From Dave Morrison at NASA...
NEO News (12/28/07) Odds of Mars Impact Increase
Date Released: Friday, December 28, 2007
Source: Jet Propulsion Laboratory
Updated Dec. 28, 2007 -- Astronomers have identified asteroid 2007 WD 5 in archival imagery. With these new observations, scientists at NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif have refined their trajectory estimates for the asteroid. Based on this latest analysis, the odds for the asteroid impacting Mars on Jan. 30 are now 1-in-25 -- or about 4 percent.
Note from David Morrison: In case of a close pass (but a miss), it is normal for the impact odds to increase before they drop to zero. This is because there is a time, as knowledge of the orbit improves, when the error ellipse (the uncertainty in the miss distance) shrinks while the target (in this case Mars) remains within the ellipse. Thus the change in odds of a hit from 1 in 75 to 1 in 25 does not mean it will hit -- it still has a 96% chance of missing -- but it sure is interesting! It would be even more "interesting" if the target were Earth not Mars. Think about it.
-------------------------------
WASHINGTON - Astronomers funded by NASA are monitoring the trajectory of an asteroid estimated to be 50 meters (164 feet) wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object may pass within 30,000 miles of Mars at about 6 a.m. EST (3 a.m. PST) on Jan. 30, 2008.
"Right now asteroid 2007 WD5 is about half-way between Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory."
NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," plots the orbits of these objects to determine if any could be potentially hazardous to our planet.
Asteroid 2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded Catalina Sky Survey and put on a "watch list" because its orbit passes near Earth. Further observations from both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the Magdalena Ridge Observatory in New Mexico gave scientists enough data to determine that the asteroid was not a danger to Earth, but could potentially impact Mars. This makes it a member of an interesting class of small objects that are both near Earth objects and "Mars crossers."
Because of current uncertainties about the asteroid's exact orbit, there is a 1-in-75 chance of 2007 WD5 impacting Mars. If this unlikely event were to occur, it would be somewhere within a broad swath across the planet north of where the Opportunity rover is located.
"We estimate such impacts occur on Mars every thousand years or so," said Steve Chesley, a scientist at JPL. "If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 30,000 miles per hour and might create a crater more than half-a-mile wide." The Mars Rover Opportunity is exploring a crater approximately this size right now.
Such a collision could release about three megatons of energy. Scientists believe an event of comparable magnitude occurred here on Earth in 1908 in Tunguska, Siberia, but no crater was created. The object was disintegrated by Earth's thicker atmosphere before it hit the ground, although the air blast devastated a large area of unpopulated forest.
NASA and its partners will continue to track asteroid 2007 WD5 and will provide an update in January when further information is available. For more information on the Near Earth Object program, visit: http://neo.jpl.nasa.gov/.
An audio interview/podcast regarding 2007 WD5 is available at: http://www.jpl.nasa.gov/multimedia/podcast/mars-asteroid-20071221/
A videofile related to this story is available on NASA TV and the Web. For information and schedules, visit: http://www.nasa.gov/ntv.
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+++++++++++++++++++++++++++++++++++++++++++
NEO News (now in its fourteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.
31 December 2007
21 December 2007
Planetary Society Blog Update on 2007 WD5 (with additional Chesley comments)
From the Planetary Society Blog (Emily Lakdawalla):
"WD5 is approximately 50 meters in diameter, so if it did hit, it would be a good-sized bang, producing a crater about a kilometer in diameter. (This is pretty close to the size of Victoria crater, Opportunity's haunt.) Chesley estimates that such a bang happens on Mars about once every thousand years."
"However, Chesley says that this size of an impact should create a dust plume that could be detected by one of the orbiters; even the rovers could detect a change in the dust component of the sky. And of course a 1-kilometer crater would be a pretty big target for HiRISE and CRISM on Mars Reconnaissance Orbiter -- in fact, that's quite big enough to be an interesting target for all the cameras on all the orbiters at Mars. You'd probably need to spot it first with one of the lower-resolution cameras, then zero in for a detailed look with one of the higher-resolution ones."
Link: Planetary Society Blog Entry 21 December 2007: "Alert the Martian Defense Force!"
"WD5 is approximately 50 meters in diameter, so if it did hit, it would be a good-sized bang, producing a crater about a kilometer in diameter. (This is pretty close to the size of Victoria crater, Opportunity's haunt.) Chesley estimates that such a bang happens on Mars about once every thousand years."
"However, Chesley says that this size of an impact should create a dust plume that could be detected by one of the orbiters; even the rovers could detect a change in the dust component of the sky. And of course a 1-kilometer crater would be a pretty big target for HiRISE and CRISM on Mars Reconnaissance Orbiter -- in fact, that's quite big enough to be an interesting target for all the cameras on all the orbiters at Mars. You'd probably need to spot it first with one of the lower-resolution cameras, then zero in for a detailed look with one of the higher-resolution ones."
Link: Planetary Society Blog Entry 21 December 2007: "Alert the Martian Defense Force!"
JPL News Release and PodCast on 2007 WD5
The current position of asteroid 2007 WD5, with its orbit shown in blue. The asteroid's orbit stretches from just outside the Earth's orbit at its closest point to the Sun, to the outer reaches of the asteroid belt at its farthest.
This artist rendering uses an arrow to show the predicted path of the asteroid on Jan. 30, 2008, and the orange swath indicates the area it is expected to pass through. Mars may or may not be in its path. Image credit: NASA/JPL
Link: JPL New Release
Link: JPL Podcast
NASA News release on 2007 WD5
From the article...
Astronomers funded by NASA are monitoring the trajectory of an asteroid estimated to be 164-feet wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object may pass within 30,000 miles of Mars at about 6 a.m. EST on Jan. 30, 2008.
"Right now asteroid 2007 WD5 is about half-way between the Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory."
Asteroid 2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded Catalina Sky Survey and put on a "watch list" because its orbit passes near the Earth. Further observations from both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the Magdalena Ridge Observatory in New Mexico gave scientists enough data to determine that the asteroid was not a danger to Earth, but could potentially impact Mars. This makes it a member of an interesting class of small objects that are both Near Earth Objects and “Mars crossers."
Because of current uncertainties about the asteroid's exact orbit, there is a 1-in-75 chance of 2007 WD5 impacting Mars. If this unlikely event were to occur, it would be somewhere within a broad swath across the planet north of where the Opportunity rover is.
"Astronomers Monitor Asteroid to Pass Near Mars"
NASA
21 December 2007
Link: NASA News Release
Astronomers funded by NASA are monitoring the trajectory of an asteroid estimated to be 164-feet wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object may pass within 30,000 miles of Mars at about 6 a.m. EST on Jan. 30, 2008.
"Right now asteroid 2007 WD5 is about half-way between the Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory."
Asteroid 2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded Catalina Sky Survey and put on a "watch list" because its orbit passes near the Earth. Further observations from both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the Magdalena Ridge Observatory in New Mexico gave scientists enough data to determine that the asteroid was not a danger to Earth, but could potentially impact Mars. This makes it a member of an interesting class of small objects that are both Near Earth Objects and “Mars crossers."
Because of current uncertainties about the asteroid's exact orbit, there is a 1-in-75 chance of 2007 WD5 impacting Mars. If this unlikely event were to occur, it would be somewhere within a broad swath across the planet north of where the Opportunity rover is.
"Astronomers Monitor Asteroid to Pass Near Mars"
NASA
21 December 2007
Link: NASA News Release
Update on Tunguska Mars (2007 WD5) Close Approach
My colleagues at SpaceWorks have done some quick propagation of 2007 WD5 using our own internal trajectory propagator. Here are some preliminary results using our IHOP (Interplanetary High-fidelity Orbit Propagator) tool:
Using an internally-developed orbit propagation tool, SpaceWorks Engineering, Inc. (SEI) has verified the predicted date for the 2007 WD5 close approach to Mars on January 30, 2008. Starting from the publicly available NASA JPL HORIZONS system orbital elements for 2007 WD5 for December 21, 2007, IHOP predicts that the asteroid 2007 WD5 will pass within 51,720 km (32,137 miles) of Mars on Wednesday, January 30, 2008 at 4:10 AM Eastern Standard Time-EST (09:10:22.1 UTC, Julian date 2454495.88220).
The internal tool, dubbed IHOP (Interplanetary High-fidelity Orbit Propagator), is a Java-based n-body propagator that utilizes a 7th/8th order Runge-Kutta-Fehlberg numerical integrator to propagate small bodies in the solar system. The orbit propagator includes the gravitational accelerations induced by the sun, the planets, and Earth's moon.
Link: SpaceWorks Engineering, Inc. (SEI)
Using an internally-developed orbit propagation tool, SpaceWorks Engineering, Inc. (SEI) has verified the predicted date for the 2007 WD5 close approach to Mars on January 30, 2008. Starting from the publicly available NASA JPL HORIZONS system orbital elements for 2007 WD5 for December 21, 2007, IHOP predicts that the asteroid 2007 WD5 will pass within 51,720 km (32,137 miles) of Mars on Wednesday, January 30, 2008 at 4:10 AM Eastern Standard Time-EST (09:10:22.1 UTC, Julian date 2454495.88220).
The internal tool, dubbed IHOP (Interplanetary High-fidelity Orbit Propagator), is a Java-based n-body propagator that utilizes a 7th/8th order Runge-Kutta-Fehlberg numerical integrator to propagate small bodies in the solar system. The orbit propagator includes the gravitational accelerations induced by the sun, the planets, and Earth's moon.
Link: SpaceWorks Engineering, Inc. (SEI)
Follow on Tunguska Mars from Dave Morrison's NEO News
From Dave Morrison's NEO News (12/21/07):
NEO News (12/21/07) "Tunguska" on Mars?
Remarkably, the Spaceguard Survey has discovered a small NEA that might hit Mars, not Earth, Orbit calculations from JPL indicate that Asteroid 2007 WD5 is on a trajectory that will bring it close to Mars on January 30, with a chance of hitting (based on the current uncertainty in the orbit) of better than 1%. Only once (3 years ago) has the orbital analysis of a NEA indicated a higher probability of impact, and the target then was Earth. For about two days around Christmas, 2004, the calculated impact probability for NEA Apophis was better than 1%, reaching a maximum of slightly greater than 1 in 50. Of course, additional orbital data then showed that while Apophis would come close in April 2029, it would not hit. The same thing will probably happen with this orbital analysis of 2007 WD5. But those of us in the business of surveying for possible impacts must always consider the possibility of a hit, even if the odds are against it. Should 2007 WD5 actually hit Mars, it would have an impact energy similar to that of the 1908 Tunguska impact on Earth, making a roughly 1-km-diameter crater. This crater, with its freshly exposed ejecta, would be extremely interesting to study from several spacecraft now in orbit around Mars. We can hope that this might happen, providing us a new window into the martian subsurface -- but the most likely ending for this story will be a miss, with 2007 WD5 quickly fading from memory.
Below are two press stories about 2007 WD5, and another reporting on the work of Mark Boslough on Tunguska, which was discussed in NEO News for December 18.
David Morrison
=====================================
ASTEROID ON TRACK FOR POSSIBLE MARS HIT
By John Johnson Jr., Los Angeles Times Staff Writer
December 21, 2007
Talk about your cosmic pileups. An asteroid similar to the one that flattened forests in Siberia in 1908 could plow into Mars next month, scientists said Thursday.
Researchers attached to NASA's Near-Earth Object Program, who sometimes jokingly call themselves the Solar System Defense Team, have been tracking the asteroid since its discovery in late November. The scientists, at the Jet Propulsion Laboratory in La Cañada Flintridge, put the chances that it will hit the Red Planet on Jan. 30 at about 1 in 75.
A 1-in-75 shot is "wildly unusual," said Steve Chesley, an astronomer with the Near-Earth Object office, which routinely tracks about 5,000 objects in Earth's neighborhood. "We're used to dealing with odds like one-in-a-million," Chesley said. "Something with a one-in-a-hundred chance makes us sit up straight in our chairs."
The asteroid, designated 2007 WD5, is about 160 feet across, which puts it in the range of the space rock that exploded over Siberia. That explosion, the largest impact event in recent history, felled 80 million trees over 830 square miles.
The Tunguska object broke up in midair, but the Martian atmosphere is so thin that an asteroid would probably plummet to the surface, digging a crater half a mile wide, Chesley said.
The impact would probably send dust high into the atmosphere, scientists said. Depending on where the asteroid hit, such a plume might be visible through telescopes on Earth, Chesley said. The Mars Reconnaissance Orbiter, which is mapping the planet, would have a front-row seat. And NASA's two JPL-built rovers, Opportunity and Spirit, might be able to take pictures from the ground.
Because scientists have never observed an asteroid impact -- the closest thing being the 1994 collision of comet Shoemaker-Levy with Jupiter -- such a collision on Mars would produce a "scientific bonanza," Chesley said. The asteroid is now behind the moon, he said, so it will be almost two weeks before observers can plot its course more accurately.
The possibility of an impact has the Solar System Defense Team excited. "Normally, we're rooting against the asteroid," when it has Earth in its cross hairs, Chesley said. "This time we're rooting for the asteroid to hit."
==============================
ASTEROID MAY HIT MARS IN NEXT MONTH
By Alicia Chang (MSNBC & AP)
LOS ANGELES (AP) - Mars could be in for an asteroid hit. A newly discovered hunk of space rock has a 1 in 75 chance of slamming into the Red Planet on Jan. 30, scientists said Thursday.
"These odds are extremely unusual. We frequently work with really long odds when we track ... threatening asteroids," said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory.
The asteroid, known as 2007 WD5, was discovered in late November and is similar in size to an object that hit remote central Siberia in 1908, unleashing energy equivalent to a 15-megaton nuclear bomb and wiping out 60 million trees.
Scientists tracking the asteroid, currently halfway between Earth and Mars, initially put the odds of impact at 1 in 350 but increased the chances this week. Scientists expect the odds to diminish again early next month after getting new observations of the asteroid's orbit, Chesley said. "We know that it's going to fly by Mars and most likely going to miss, but there's a possibility of an impact," he said.
If the asteroid does smash into Mars, it will probably hit near the equator close to where the rover Opportunity has been exploring the Martian plains since 2004. The robot is not in danger because it lies outside the impact zone. Speeding at 8 miles a second, a collision would carve a hole the size of the famed Meteor Crater in Arizona.
In 1994, fragments of the comet Shoemaker-Levy 9 smacked into Jupiter, creating a series of overlapping fireballs in space. Astronomers have yet to witness an asteroid impact with another planet. "Unlike an Earth impact, we're not afraid, but we're excited," Chesley said.
===================================
SMALL ASTEROIDS POSE BIG NEW THREAT
By Charles Q. Choi, SPACE.com
19 December 2007
The infamous Tunguska explosion, which mysteriously leveled an area of Siberian forest nearly the size of Tokyo a century ago, might have been caused by an impacting asteroid far smaller than previously thought.
The fact that a relatively small asteroid could still cause such a massive explosion suggests "we should be making more efforts at detecting the smaller ones than we have till now," said researcher Mark Boslough, a physicist at Sandia National Laboratory in Albuquerque, N.M.
The explosion near the Podkamennaya Tunguska River on June 30, 1908, flattened some 500,000 acres (2,000 square kilometers) of Siberian forest. Scientists calculated the Tunguska explosion could have been roughly as strong as 10 to 20 megatons of TNT - 1,000 times more powerful than the atom bomb dropped on Hiroshima.
Wild theories have been bandied about for a century regarding what caused the Tunguska explosion, including a UFO crash, antimatter, a black hole and famed inventor Nikola Tesla's "death ray." In the last decade, researchers have conjectured the event was triggered by an asteroid exploding in Earth's atmosphere that was roughly 100 feet wide (30 meters) and 560,000 metric tons in mass - more than 10 times that of the Titanic.
The space rock is thought to have blown up above the surface, only fragments possibly striking the ground.
Now new supercomputer simulations suggest "the asteroid that caused the extensive damage was much smaller than we had thought," Boslough said. Specifically, he and his colleagues say it would have been a factor of three or four smaller in mass and perhaps 65 feet (20 meters) in diameter.
The simulations run on Sandia's Red Storm supercomputer - the third fastest in the world - detail how an asteroid that explodes as it runs into Earth's atmosphere will generate a supersonic jet of expanding superheated gas. This fireball would have caused blast waves that were stronger at the surface than previously thought.
At the same time, previous estimates seem to have overstated the devastation the event caused. The forest back then was not healthy, according to foresters, "and it doesn't take as much energy to blow down a diseased tree than a healthy tree," Boslough said. In addition, the winds from the explosion would naturally get amplified above ridgelines, making the explosion seem more powerful than it actually was. What scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons, he explained.
All in all, the researchers suggest that smaller asteroids may pose a greater danger than previously believed. Moreover, "there are a lot more objects that size," Boslough told SPACE.com.
NASA Ames Research Center planetary scientist and astrobiologist David Morrison, who did not participate in this study, said, "If he's right, we can expect more Tunguska-sized explosions - perhaps every couple of centuries instead of every millennia or two." He added, "It raises the bar in the long term - ultimately, we'd like to have a survey system that can detect things this small."
Boslough and his colleagues detailed their findings at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon has been accepted for publication in the International Journal of Impact Engineering.
--
+++++++++++++++++++++++++++++++++++++++++++
NEO News (now in its fourteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.
NEO News (12/21/07) "Tunguska" on Mars?
Remarkably, the Spaceguard Survey has discovered a small NEA that might hit Mars, not Earth, Orbit calculations from JPL indicate that Asteroid 2007 WD5 is on a trajectory that will bring it close to Mars on January 30, with a chance of hitting (based on the current uncertainty in the orbit) of better than 1%. Only once (3 years ago) has the orbital analysis of a NEA indicated a higher probability of impact, and the target then was Earth. For about two days around Christmas, 2004, the calculated impact probability for NEA Apophis was better than 1%, reaching a maximum of slightly greater than 1 in 50. Of course, additional orbital data then showed that while Apophis would come close in April 2029, it would not hit. The same thing will probably happen with this orbital analysis of 2007 WD5. But those of us in the business of surveying for possible impacts must always consider the possibility of a hit, even if the odds are against it. Should 2007 WD5 actually hit Mars, it would have an impact energy similar to that of the 1908 Tunguska impact on Earth, making a roughly 1-km-diameter crater. This crater, with its freshly exposed ejecta, would be extremely interesting to study from several spacecraft now in orbit around Mars. We can hope that this might happen, providing us a new window into the martian subsurface -- but the most likely ending for this story will be a miss, with 2007 WD5 quickly fading from memory.
Below are two press stories about 2007 WD5, and another reporting on the work of Mark Boslough on Tunguska, which was discussed in NEO News for December 18.
David Morrison
=====================================
ASTEROID ON TRACK FOR POSSIBLE MARS HIT
By John Johnson Jr., Los Angeles Times Staff Writer
December 21, 2007
Talk about your cosmic pileups. An asteroid similar to the one that flattened forests in Siberia in 1908 could plow into Mars next month, scientists said Thursday.
Researchers attached to NASA's Near-Earth Object Program, who sometimes jokingly call themselves the Solar System Defense Team, have been tracking the asteroid since its discovery in late November. The scientists, at the Jet Propulsion Laboratory in La Cañada Flintridge, put the chances that it will hit the Red Planet on Jan. 30 at about 1 in 75.
A 1-in-75 shot is "wildly unusual," said Steve Chesley, an astronomer with the Near-Earth Object office, which routinely tracks about 5,000 objects in Earth's neighborhood. "We're used to dealing with odds like one-in-a-million," Chesley said. "Something with a one-in-a-hundred chance makes us sit up straight in our chairs."
The asteroid, designated 2007 WD5, is about 160 feet across, which puts it in the range of the space rock that exploded over Siberia. That explosion, the largest impact event in recent history, felled 80 million trees over 830 square miles.
The Tunguska object broke up in midair, but the Martian atmosphere is so thin that an asteroid would probably plummet to the surface, digging a crater half a mile wide, Chesley said.
The impact would probably send dust high into the atmosphere, scientists said. Depending on where the asteroid hit, such a plume might be visible through telescopes on Earth, Chesley said. The Mars Reconnaissance Orbiter, which is mapping the planet, would have a front-row seat. And NASA's two JPL-built rovers, Opportunity and Spirit, might be able to take pictures from the ground.
Because scientists have never observed an asteroid impact -- the closest thing being the 1994 collision of comet Shoemaker-Levy with Jupiter -- such a collision on Mars would produce a "scientific bonanza," Chesley said. The asteroid is now behind the moon, he said, so it will be almost two weeks before observers can plot its course more accurately.
The possibility of an impact has the Solar System Defense Team excited. "Normally, we're rooting against the asteroid," when it has Earth in its cross hairs, Chesley said. "This time we're rooting for the asteroid to hit."
==============================
ASTEROID MAY HIT MARS IN NEXT MONTH
By Alicia Chang (MSNBC & AP)
LOS ANGELES (AP) - Mars could be in for an asteroid hit. A newly discovered hunk of space rock has a 1 in 75 chance of slamming into the Red Planet on Jan. 30, scientists said Thursday.
"These odds are extremely unusual. We frequently work with really long odds when we track ... threatening asteroids," said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory.
The asteroid, known as 2007 WD5, was discovered in late November and is similar in size to an object that hit remote central Siberia in 1908, unleashing energy equivalent to a 15-megaton nuclear bomb and wiping out 60 million trees.
Scientists tracking the asteroid, currently halfway between Earth and Mars, initially put the odds of impact at 1 in 350 but increased the chances this week. Scientists expect the odds to diminish again early next month after getting new observations of the asteroid's orbit, Chesley said. "We know that it's going to fly by Mars and most likely going to miss, but there's a possibility of an impact," he said.
If the asteroid does smash into Mars, it will probably hit near the equator close to where the rover Opportunity has been exploring the Martian plains since 2004. The robot is not in danger because it lies outside the impact zone. Speeding at 8 miles a second, a collision would carve a hole the size of the famed Meteor Crater in Arizona.
In 1994, fragments of the comet Shoemaker-Levy 9 smacked into Jupiter, creating a series of overlapping fireballs in space. Astronomers have yet to witness an asteroid impact with another planet. "Unlike an Earth impact, we're not afraid, but we're excited," Chesley said.
===================================
SMALL ASTEROIDS POSE BIG NEW THREAT
By Charles Q. Choi, SPACE.com
19 December 2007
The infamous Tunguska explosion, which mysteriously leveled an area of Siberian forest nearly the size of Tokyo a century ago, might have been caused by an impacting asteroid far smaller than previously thought.
The fact that a relatively small asteroid could still cause such a massive explosion suggests "we should be making more efforts at detecting the smaller ones than we have till now," said researcher Mark Boslough, a physicist at Sandia National Laboratory in Albuquerque, N.M.
The explosion near the Podkamennaya Tunguska River on June 30, 1908, flattened some 500,000 acres (2,000 square kilometers) of Siberian forest. Scientists calculated the Tunguska explosion could have been roughly as strong as 10 to 20 megatons of TNT - 1,000 times more powerful than the atom bomb dropped on Hiroshima.
Wild theories have been bandied about for a century regarding what caused the Tunguska explosion, including a UFO crash, antimatter, a black hole and famed inventor Nikola Tesla's "death ray." In the last decade, researchers have conjectured the event was triggered by an asteroid exploding in Earth's atmosphere that was roughly 100 feet wide (30 meters) and 560,000 metric tons in mass - more than 10 times that of the Titanic.
The space rock is thought to have blown up above the surface, only fragments possibly striking the ground.
Now new supercomputer simulations suggest "the asteroid that caused the extensive damage was much smaller than we had thought," Boslough said. Specifically, he and his colleagues say it would have been a factor of three or four smaller in mass and perhaps 65 feet (20 meters) in diameter.
The simulations run on Sandia's Red Storm supercomputer - the third fastest in the world - detail how an asteroid that explodes as it runs into Earth's atmosphere will generate a supersonic jet of expanding superheated gas. This fireball would have caused blast waves that were stronger at the surface than previously thought.
At the same time, previous estimates seem to have overstated the devastation the event caused. The forest back then was not healthy, according to foresters, "and it doesn't take as much energy to blow down a diseased tree than a healthy tree," Boslough said. In addition, the winds from the explosion would naturally get amplified above ridgelines, making the explosion seem more powerful than it actually was. What scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons, he explained.
All in all, the researchers suggest that smaller asteroids may pose a greater danger than previously believed. Moreover, "there are a lot more objects that size," Boslough told SPACE.com.
NASA Ames Research Center planetary scientist and astrobiologist David Morrison, who did not participate in this study, said, "If he's right, we can expect more Tunguska-sized explosions - perhaps every couple of centuries instead of every millennia or two." He added, "It raises the bar in the long term - ultimately, we'd like to have a survey system that can detect things this small."
Boslough and his colleagues detailed their findings at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon has been accepted for publication in the International Journal of Impact Engineering.
--
+++++++++++++++++++++++++++++++++++++++++++
NEO News (now in its fourteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.
Article: "Asteroid May Hit Mars in Next Month"
Our firm, SpaceWorks Engineering, Inc. (SEI) has been reviewing this object and may have some additional analysis on this object.
From the article...
A newly discovered hunk of space rock has a 1 in 75 chance of slamming into the Red Planet on Jan. 30, scientists said Thursday.
"These odds are extremely unusual. We frequently work with really long odds when we track ... threatening asteroids," said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory.
The asteroid, known as 2007 WD5, was discovered in late November and is similar in size to an object that hit remote central Siberia in 1908, unleashing energy equivalent to a 15-megaton nuclear bomb and wiping out 60 million trees.
Scientists tracking the asteroid, currently halfway between Earth and Mars, initially put the odds of impact at 1 in 350 but increased the chances this week. Scientists expect the odds to diminish again early next month after getting new observations of the asteroid's orbit, Chesley said.
"Asteroid May Hit Mars in Next Month"
Alicia Chang
Associated Press
20 December 2007
Link: Article
Another article from the LA Times has more information:
The asteroid is now behind the moon, he said, so it will be almost two weeks before observers can plot its course more accurately.
"Normally, we're rooting against the asteroid," when it has Earth in its cross hairs, Chesley said. "This time we're rooting for the asteroid to hit."
"Asteroid on track for possible Mars hit"
John Johnson Jr.
Los Angeles Times Staff Writer
21 December 2007
Link: LA Times article
Link: JPL Orbit Diagram of 2007 WD5
From the article...
A newly discovered hunk of space rock has a 1 in 75 chance of slamming into the Red Planet on Jan. 30, scientists said Thursday.
"These odds are extremely unusual. We frequently work with really long odds when we track ... threatening asteroids," said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory.
The asteroid, known as 2007 WD5, was discovered in late November and is similar in size to an object that hit remote central Siberia in 1908, unleashing energy equivalent to a 15-megaton nuclear bomb and wiping out 60 million trees.
Scientists tracking the asteroid, currently halfway between Earth and Mars, initially put the odds of impact at 1 in 350 but increased the chances this week. Scientists expect the odds to diminish again early next month after getting new observations of the asteroid's orbit, Chesley said.
"Asteroid May Hit Mars in Next Month"
Alicia Chang
Associated Press
20 December 2007
Link: Article
Another article from the LA Times has more information:
The asteroid is now behind the moon, he said, so it will be almost two weeks before observers can plot its course more accurately.
"Normally, we're rooting against the asteroid," when it has Earth in its cross hairs, Chesley said. "This time we're rooting for the asteroid to hit."
"Asteroid on track for possible Mars hit"
John Johnson Jr.
Los Angeles Times Staff Writer
21 December 2007
Link: LA Times article
Link: JPL Orbit Diagram of 2007 WD5
19 December 2007
NEO News (12/19/07) Tunguska Revision & New Book
From David Morrison...
NEO News (12/19/07) Tunguska Revision & New Book
Season's greetings and best wishes for a good new year!
The main story in this edition of NEO News concerns a proposed downsizing of the energy of the 1908 Tunguska airburst, with associated increase in the expected frequency of such impacts. Mark Boslough of Sandia has generated supercomputer simulations of the Tunguska atmospheric explosion. In part his models require less energy in the explosion because he includes the substantial downward momentum of the rocky impactor, rather then modeling it as a stationary explosion. If this revision (down to an estimated energy of 3-5 megatons, and a corresponding diameter of about 50 meters) is correct, the expected frequency of such impacts changes, from once in a couple of millennia to once in a few hundred years. If smaller impactors can do the damage previously associated with larger ones, of course, the total hazard from such impacts is increased.
The second item below is an announcement of publication of a new multi-author book "Comet/Asteroid Impacts and Human Society."
David Morrison
===================================
NEW ESTIMATE OF TUNGUSKA IMPACTOR SIZE
Sandia: December 17, 2007
ALBUQUERQUE, N.M. - The stunning amount of forest devastation at Tunguska a century ago in Siberia may have been caused by an asteroid only a fraction as large as previously published estimates, Sandia National Laboratories supercomputer simulations suggest.
"The asteroid that caused the extensive damage was much smaller than we had thought," says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. "That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed." Because smaller asteroids approach Earth statistically more frequently than larger ones, he says, "We should be making more efforts at detecting the smaller ones than we have till now."
The new simulation -- which more closely matches the widely known facts of destruction than earlier models -- shows that the center of mass of an asteroid exploding above the ground is transported downward at speeds faster than sound. It takes the form of a high-temperature jet of expanding gas called a fireball. This causes stronger blast waves and thermal radiation pulses at the surface than would be predicted by an explosion limited to the height at which the blast was initiated.
"Our understanding was oversimplified," says Boslough, "We no longer have to make the same simplifying assumptions, because present-day supercomputers allow us to do things with high resolution in 3-D. Everything gets clearer as you look at things with more refined tools."
The new interpretation also accounts for the fact that winds were amplified above ridgelines where trees tended to be blown down, and that the forest at the time of the explosion, according to foresters, was not healthy. Thus previous scientific estimates had overstated the devastation caused by the asteroid, since topographic and ecologic factors contributing to the result had not been taken into account.
"There's actually less devastation than previously thought," says Boslough, "but it was caused by a far smaller asteroid. Unfortunately, it's not a complete wash in terms of the potential hazard, because there are more smaller asteroids than larger ones."
Boslough and colleagues achieved fame more than a decade ago by accurately predicting that that the fireball caused by the intersection of the comet Shoemaker-Levy 9 with Jupiter would be observable from Earth.
Simulations show that the material of an incoming asteroid is compressed by the increasing resistance of Earth's atmosphere. As it penetrates deeper, the more and more resistant atmospheric wall causes it to explode as an airburst that precipitates the downward flow of heated gas.
Because of the additional energy transported toward the surface by the fireball, what scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons. The physical size of the asteroid, says Boslough, depends upon its speed and whether it is porous or nonporous, icy or waterless, and other material characteristics.
"Any strategy for defense or deflection should take into consideration this revised understanding of the mechanism of explosion," says Boslough.
One of most prominent papers in estimating frequency of impact was published five years ago in Nature by Sandia researcher Dick Spalding and his colleagues, from satellite data on explosions in atmosphere. "They can count those events and estimate frequencies of arrival through probabilistic arguments," says Boslough.
The work was presented at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon, co-authored by Sandia researcher Dave Crawford and entitled "Low-altitude airbursts and the impact threat" has been accepted for publication in the International Journal of Impact Engineering.
The research was paid for by Sandia's Laboratory-Directed Research and Development office.
==================================
NEW BOOK ON IMPACTS AND HUMAN SOCIETY
During the first days of December 2004, a multidisciplinary workshop was held in the town of La Laguna on the Canary isle of Tenerife with the title "Comet/Asteroid Impacts and Human Society". This was funded as part of a project with the same name by ICSU, the International Council for Science. The driving force behind the project is the realization of a need to support the development of both national and international policies regarding the impact hazard. And the direct goal of the workshop was to bring together experts on as wide a range of topics as possible with a bearing on all issues from the astronomical observations and dynamical theories to the down-to-Earth aspects of disaster planning and information chains.
The papers presented at this workshop - both keynote and research talks - have been refereed and are now available as a Springer volume entitled "Comet/Asteroid Impacts and Human Society - an Interdisciplinary Approach" (ISBN 978-3-540-32709-7), edited by Peter Bobrowsky and Hans Rickman. They were the leaders of the project and main organizers of the workshop, representing the International Union of Geological Sciences and the International Astronomical Union, respectively. The book has been prepared as a technical document describing the state of knowledge in many different fields in a way that should be understandable across all borders. It should not be perceived as the end of an effort but rather as the beginning of something new, i.e., a concerted effort to develop an interdisciplinary scientific field and bring the knowledge to both citizens and decision makers of society.
Hans Rickman
--
+++++++++++++++++++++++++++++++++++++++++++
NEO News (now in its fourteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.
NEO News (12/19/07) Tunguska Revision & New Book
Season's greetings and best wishes for a good new year!
The main story in this edition of NEO News concerns a proposed downsizing of the energy of the 1908 Tunguska airburst, with associated increase in the expected frequency of such impacts. Mark Boslough of Sandia has generated supercomputer simulations of the Tunguska atmospheric explosion. In part his models require less energy in the explosion because he includes the substantial downward momentum of the rocky impactor, rather then modeling it as a stationary explosion. If this revision (down to an estimated energy of 3-5 megatons, and a corresponding diameter of about 50 meters) is correct, the expected frequency of such impacts changes, from once in a couple of millennia to once in a few hundred years. If smaller impactors can do the damage previously associated with larger ones, of course, the total hazard from such impacts is increased.
The second item below is an announcement of publication of a new multi-author book "Comet/Asteroid Impacts and Human Society."
David Morrison
===================================
NEW ESTIMATE OF TUNGUSKA IMPACTOR SIZE
Sandia: December 17, 2007
ALBUQUERQUE, N.M. - The stunning amount of forest devastation at Tunguska a century ago in Siberia may have been caused by an asteroid only a fraction as large as previously published estimates, Sandia National Laboratories supercomputer simulations suggest.
"The asteroid that caused the extensive damage was much smaller than we had thought," says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. "That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed." Because smaller asteroids approach Earth statistically more frequently than larger ones, he says, "We should be making more efforts at detecting the smaller ones than we have till now."
The new simulation -- which more closely matches the widely known facts of destruction than earlier models -- shows that the center of mass of an asteroid exploding above the ground is transported downward at speeds faster than sound. It takes the form of a high-temperature jet of expanding gas called a fireball. This causes stronger blast waves and thermal radiation pulses at the surface than would be predicted by an explosion limited to the height at which the blast was initiated.
"Our understanding was oversimplified," says Boslough, "We no longer have to make the same simplifying assumptions, because present-day supercomputers allow us to do things with high resolution in 3-D. Everything gets clearer as you look at things with more refined tools."
The new interpretation also accounts for the fact that winds were amplified above ridgelines where trees tended to be blown down, and that the forest at the time of the explosion, according to foresters, was not healthy. Thus previous scientific estimates had overstated the devastation caused by the asteroid, since topographic and ecologic factors contributing to the result had not been taken into account.
"There's actually less devastation than previously thought," says Boslough, "but it was caused by a far smaller asteroid. Unfortunately, it's not a complete wash in terms of the potential hazard, because there are more smaller asteroids than larger ones."
Boslough and colleagues achieved fame more than a decade ago by accurately predicting that that the fireball caused by the intersection of the comet Shoemaker-Levy 9 with Jupiter would be observable from Earth.
Simulations show that the material of an incoming asteroid is compressed by the increasing resistance of Earth's atmosphere. As it penetrates deeper, the more and more resistant atmospheric wall causes it to explode as an airburst that precipitates the downward flow of heated gas.
Because of the additional energy transported toward the surface by the fireball, what scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons. The physical size of the asteroid, says Boslough, depends upon its speed and whether it is porous or nonporous, icy or waterless, and other material characteristics.
"Any strategy for defense or deflection should take into consideration this revised understanding of the mechanism of explosion," says Boslough.
One of most prominent papers in estimating frequency of impact was published five years ago in Nature by Sandia researcher Dick Spalding and his colleagues, from satellite data on explosions in atmosphere. "They can count those events and estimate frequencies of arrival through probabilistic arguments," says Boslough.
The work was presented at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon, co-authored by Sandia researcher Dave Crawford and entitled "Low-altitude airbursts and the impact threat" has been accepted for publication in the International Journal of Impact Engineering.
The research was paid for by Sandia's Laboratory-Directed Research and Development office.
==================================
NEW BOOK ON IMPACTS AND HUMAN SOCIETY
During the first days of December 2004, a multidisciplinary workshop was held in the town of La Laguna on the Canary isle of Tenerife with the title "Comet/Asteroid Impacts and Human Society". This was funded as part of a project with the same name by ICSU, the International Council for Science. The driving force behind the project is the realization of a need to support the development of both national and international policies regarding the impact hazard. And the direct goal of the workshop was to bring together experts on as wide a range of topics as possible with a bearing on all issues from the astronomical observations and dynamical theories to the down-to-Earth aspects of disaster planning and information chains.
The papers presented at this workshop - both keynote and research talks - have been refereed and are now available as a Springer volume entitled "Comet/Asteroid Impacts and Human Society - an Interdisciplinary Approach" (ISBN 978-3-540-32709-7), edited by Peter Bobrowsky and Hans Rickman. They were the leaders of the project and main organizers of the workshop, representing the International Union of Geological Sciences and the International Astronomical Union, respectively. The book has been prepared as a technical document describing the state of knowledge in many different fields in a way that should be understandable across all borders. It should not be perceived as the end of an effort but rather as the beginning of something new, i.e., a concerted effort to develop an interdisciplinary scientific field and bring the knowledge to both citizens and decision makers of society.
Hans Rickman
--
+++++++++++++++++++++++++++++++++++++++++++
NEO News (now in its fourteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.
International Primitive Body Exploration Working Group (IPEWG): 14-16 Janaury 2008 (Okinawa, Japan)
From the conference website...
Thanks to successful development of enabling technologies for deep space exploration, missions to small solar system bodies have revolutionized our understanding of the Solar System’s origin and evolution in the last decade. At present, rendezvous, impact, landing and sample return missions to asteroids and comets such as NEAR-Shoemaker, Hayabusa, Stardust, Deep Impact, Rosetta,Dawn, EPOXI and NEXT as well as New Horizons, a fly-by mission to EKBOs, are completed or still in the middle of operation.
Also more challenging, new missions are under development or under concept studies by several space agencies including Hayabusa-2, Hayabusa Mk-II(Marco Polo), Don Quijote, OSIRIS, and Phobos-Grunt.
In addition to scientific and engineering motivations, NEO studies receive increasing interests in the context of planetary defense, deep space human spaceflight and potential in-situ resource utilization.
In 1980’s, the inter-agency coordination group for Comet Halley exploration proved that synergy of coordinated individual missions could enrich total outcomes more than each result combined.Since then, international exploration working groups participated by international space agencies have been formed and played key roles for advancing fields of solar terrestrial physics, Moon and Mars missions.
As we are entering the second golden age of the primitive body exploration in upcoming decade, now is the appropriate time to create the International Primitive Body Exploration Working Group (IPEWG) in order to promote international collaborations and to maximize outcomes of each mission. With these in mind, the first IPEWG meeting will be hosted by JAXA at Okinawa,the southern-most, tropical island in Japan. All space agencies, scientists, engineers and other interested stakeholders are cordially invited.
Session-1: Currently Operated Missions Review
(The following is a list of potential presentations)
[Asteroids]
Hayabusa
Dawn
[Comets]
Rosetta
NeXT
EPOXI
[Trans-Neptunian]
New Horizons
Session-2: Missions in Preparation & Concepts
(The following is a list of potential presentations)
[Asteroids]
Hayabusa-2
Marco Polo
OSIRIS
Phobos-Grunt
NEA Observer
Don Quijote
Small NEO Missions
Apophis Mission
NASA Human NEO
Solar Power Sail
[Comets]
Comet Surface Sample Return
Triple-F
Link: Conference Website
Thanks to successful development of enabling technologies for deep space exploration, missions to small solar system bodies have revolutionized our understanding of the Solar System’s origin and evolution in the last decade. At present, rendezvous, impact, landing and sample return missions to asteroids and comets such as NEAR-Shoemaker, Hayabusa, Stardust, Deep Impact, Rosetta,Dawn, EPOXI and NEXT as well as New Horizons, a fly-by mission to EKBOs, are completed or still in the middle of operation.
Also more challenging, new missions are under development or under concept studies by several space agencies including Hayabusa-2, Hayabusa Mk-II(Marco Polo), Don Quijote, OSIRIS, and Phobos-Grunt.
In addition to scientific and engineering motivations, NEO studies receive increasing interests in the context of planetary defense, deep space human spaceflight and potential in-situ resource utilization.
In 1980’s, the inter-agency coordination group for Comet Halley exploration proved that synergy of coordinated individual missions could enrich total outcomes more than each result combined.Since then, international exploration working groups participated by international space agencies have been formed and played key roles for advancing fields of solar terrestrial physics, Moon and Mars missions.
As we are entering the second golden age of the primitive body exploration in upcoming decade, now is the appropriate time to create the International Primitive Body Exploration Working Group (IPEWG) in order to promote international collaborations and to maximize outcomes of each mission. With these in mind, the first IPEWG meeting will be hosted by JAXA at Okinawa,the southern-most, tropical island in Japan. All space agencies, scientists, engineers and other interested stakeholders are cordially invited.
Session-1: Currently Operated Missions Review
(The following is a list of potential presentations)
[Asteroids]
Hayabusa
Dawn
[Comets]
Rosetta
NeXT
EPOXI
[Trans-Neptunian]
New Horizons
Session-2: Missions in Preparation & Concepts
(The following is a list of potential presentations)
[Asteroids]
Hayabusa-2
Marco Polo
OSIRIS
Phobos-Grunt
NEA Observer
Don Quijote
Small NEO Missions
Apophis Mission
NASA Human NEO
Solar Power Sail
[Comets]
Comet Surface Sample Return
Triple-F
Link: Conference Website
Andrei Ol'khovatov's Very Extenstive Site on Tunguska Event
Map above (taken from Yevgenii Krinov's 1949 book called "The Tunguska meteorite"), with Krinov's marks of various Tunguska manifestations
Here is a link to Andrei Ol'khovatov's site where he seems to have the latest information on the Tunguska research. Remember: next year, 30 June 2008, is the 100th anniversary of the Tunguska event.
Link: Tunguska Update
Link: Andrei Ol'khovatov's main site
Article: "Small Asteroids Pose Big New Threat"
A supercomputer simulation of a fireball that might be expected from an asteroid exploding in Earth's atmosphere, as pointed out by Sandia National Laboratories researcher Mark Boslough. Credit: Randy Montoya
From the abstract...
"Computational Modeling of Low-Altitude Airbursts," Boslough, M. [Sandia National Laboratories], American Geophysical Union 2007 Fall Meeting, San Francisco, CA, December 10-14, 2007.
New simulations of airbursts in the Earth's lower atmosphere from hypervelocity asteroid impacts suggest that a re-evaluation of the impact hazard is necessary to properly account for the enhanced damage potential relative to point-source approximations. The intent of these simulations was to explore the phenomenology associated with low-altitude airbursts and to determine whether the altitude of maximum energy deposition can be used as a reasonable estimate of the equivalent height of a point explosion. The simulations suggest that this not a good approximation, because the center of mass of an exploding projectile is transported downward in the form of a high-temperature jet of expanding gas. The jet descends by a significant fraction of the burst altitude before its velocity becomes subsonic. The time scale of this descent is similar to the time scale of the explosion itself, so the jet simultaneously couples both its translational and its radial kinetic energy to the atmosphere. Because of this downward flow, larger blast waves and stronger thermal radiation pulses are felt at the surface than would be predicted for a nuclear explosion of the same yield at the same height. For impacts with a kinetic energy above some threshold, the hot jet of vaporized projectile (the descending "fireball") makes contact with the Earth's surface, where it expands radially. During the time of radial expansion, the fireball can maintain temperatures well above the melting temperature of silicate minerals, and its radial velocity can exceed the sound speed in air. Surface materials can ablate by radiative/convective melting under these conditions, and then quench rapidly to form glass after the fireball cools and recedes. One possible example of an airburst glass is the Libyan Desert Glass of western Egypt. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.
From the article...
Now new supercomputer simulations suggest "the asteroid that caused the extensive damage was much smaller than we had thought," Boslough [Mark Boslough, a physicist at Sandia National Laboratory in Albuquerque, N.M.] said. Specifically, he and his colleagues say it would have been a factor of three or four smaller in mass and perhaps 65 feet (20 meters) in diameter.
The simulations run on Sandia's Red Storm supercomputer — the third fastest in the world — detail how an asteroid that explodes as it runs into Earth's atmosphere will generate a supersonic jet of expanding superheated gas. This fireball would have caused blast waves that were stronger at the surface than previously thought.
At the same time, previous estimates seem to have overstated the devastation the event caused. The forest back then was not healthy, according to foresters, "and it doesn't take as much energy to blow down a diseased tree than a healthy tree," Boslough said. In addition, the winds from the explosion would naturally get amplified above ridgelines, making the explosion seem more powerful than it actually was. What scientists had thought to be an explosion between 10 and 20 megatons was more likely only three to five megatons, he explained.
All in all, the researchers suggest that smaller asteroids may pose a greater danger than previously believed. Moreover, "there are a lot more objects that size," Boslough told SPACE.com.
NASA Ames Research Center planetary scientist and astrobiologist David Morrison, who did not participate in this study, said, "If he's right, we can expect more Tunguska-sized explosions — perhaps every couple of centuries instead of every millennia or two." He added, "It raises the bar in the long term — ultimately, we'd like to have a survey system that can detect things this small."
Boslough and his colleagues detailed their findings at the American Geophysical Union meeting in San Francisco on Dec. 11. A paper on the phenomenon has been accepted for publication in the International Journal of Impact Engineering.
"Small Asteroids Pose Big New Threat"
Charles Q. Choi
19 December 2007
SPACE.com
Link: Space.com Article
"Computational Modeling of Low-Altitude Airbursts," Boslough, M. [Sandia National Laboratories], American Geophysical Union 2007 Fall Meeting, San Francisco, CA, December 10-14, 2007.
"Terrestrial Impact Cratering: New Insights Into the Cratering Process From Geophysics and Geochemistry," C. Koeberl [University of Vienna], M. Boslough [Sandia National Laboratories], American Geophysical Union 2007 Fall Meeting, San Francisco, CA, December 10-14, 2007.
Link: American Geophysical Union 2007 Fall Meeting
18 December 2007
U.S. Congress to Have National Research Council Review Arecibo and NASA NEO Report
Looks as if there may be a National Research Council (NRC) review of decisions regarding Arecibo (and any closure of it) as well as the recent NASA NEO Study. From the recent US Omnibus Congressional Legislation for the FY2008 US Budget:
"In order to assist Congress in determining the optimal approach regarding the Arecibo Observatory, NASA shall contract with the National Research Council to study the issue and make recommendations. As part of its deliberations, the NRC shall review NASA's report 2006 Near-Earth Object Survey and Deflection Study - and its associated March 2007 Near-Earth Object Survey and Deflection Study as well as any other relevant literature. An interim report, with recommendations focusing primarily on the optimal approach to the survey program, shall be submitted within 15 months of enactment of this Act. The final report, including recommendations regarding the optimal approach to developing a deflection capability, shall be submitted within 21 months of enactment of this Act. The NRC study shall include an assessment of the costs of various alternatives, including options that may blend the use of different facilities (whether ground- or space-based), or involve international cooperation. Independent cost estimating should be utilized."
Link: Text of the House Amendments to Senate Amendment to H.R. 2764 – State, Foreign Operations, and Related Programs Appropriations Act, 2008 (Consolidated Appropriations Act, 2008) Division B--Commerce, Justice, Science
"In order to assist Congress in determining the optimal approach regarding the Arecibo Observatory, NASA shall contract with the National Research Council to study the issue and make recommendations. As part of its deliberations, the NRC shall review NASA's report 2006 Near-Earth Object Survey and Deflection Study - and its associated March 2007 Near-Earth Object Survey and Deflection Study as well as any other relevant literature. An interim report, with recommendations focusing primarily on the optimal approach to the survey program, shall be submitted within 15 months of enactment of this Act. The final report, including recommendations regarding the optimal approach to developing a deflection capability, shall be submitted within 21 months of enactment of this Act. The NRC study shall include an assessment of the costs of various alternatives, including options that may blend the use of different facilities (whether ground- or space-based), or involve international cooperation. Independent cost estimating should be utilized."
Link: Text of the House Amendments to Senate Amendment to H.R. 2764 – State, Foreign Operations, and Related Programs Appropriations Act, 2008 (Consolidated Appropriations Act, 2008) Division B--Commerce, Justice, Science
16 December 2007
Non-Asteroid Related: Mars Surface Habitat Video
This is not related specifically to planetary defense but to my job. From the news announcement:
SpaceWorks Engineering, Inc. (SEI) announces it has produced a new video entitled "Mars Vision: The Surface", a visualization of human exploration on the surface of Mars. This video shows the interior of a habitat where future explorers would reside during surface operations. The depicted concept is based upon a human exploration architecture for Mars designed independently in 2007 by SpaceWorks Engineering, Inc. (SEI). The lead technical author of this concept is Dr. Brad St. Germain, Director of the Advanced Concepts Group (ACG) at SEI. "Mars Vision: The Surface" video developer and SEI lead concept artist is Mr. Mark Elwood. The video is available on YouTube; please see the "SpaceWorksEng" user on YouTube. The video is also available for direct download from the links below. A technical paper is also available that describes a related notional Mars architecture as developed by SEI.
Link: SEI News Announcement
Link: "Mars Vision: The Surface" Video: YouTube
Link: "Mars Vision: The Surface" Video: Direct Download - MPEG4 (47.1 MB)
Link: "Mars Vision: The Surface" Video: Direct Download - MPEG2 (85 MB)
Link: "Mars Vision: The Surface" Video: Direct Download - AVI (42.6 MB)
SpaceWorks Engineering, Inc. (SEI) announces it has produced a new video entitled "Mars Vision: The Surface", a visualization of human exploration on the surface of Mars. This video shows the interior of a habitat where future explorers would reside during surface operations. The depicted concept is based upon a human exploration architecture for Mars designed independently in 2007 by SpaceWorks Engineering, Inc. (SEI). The lead technical author of this concept is Dr. Brad St. Germain, Director of the Advanced Concepts Group (ACG) at SEI. "Mars Vision: The Surface" video developer and SEI lead concept artist is Mr. Mark Elwood. The video is available on YouTube; please see the "SpaceWorksEng" user on YouTube. The video is also available for direct download from the links below. A technical paper is also available that describes a related notional Mars architecture as developed by SEI.
Link: SEI News Announcement
Link: "Mars Vision: The Surface" Video: YouTube
Link: "Mars Vision: The Surface" Video: Direct Download - MPEG4 (47.1 MB)
Link: "Mars Vision: The Surface" Video: Direct Download - MPEG2 (85 MB)
Link: "Mars Vision: The Surface" Video: Direct Download - AVI (42.6 MB)
14 December 2007
NASA does not select OSIRIS asteroid sample return mission for selection as Discovery Mission
From the article:
The University of Arizona has lost out on $425 million in NASA funding after the space agency selected a competing proposal for its next Discovery Class mission.
The UA's OSIRIS mission, which would have launched a spacecraft to collect and return material from a near-Earth asteroid, was one of three finalists competing for the NASA funding. NASA officials announced this week that another finalist, a moon mission known as GRAIL, will move forward.
"It was a bit of a shock, frankly," said Michael Drake, director of the UA's Lunar and Planetary Laboratory and principal investigator for OSIRIS.
The lab will continue to seek funding for the asteroid-sample-return mission, modifying the proposal based on feedback from NASA officials. The ongoing Discovery program aims to launch a mission every 12 to 24 months.
Link: Article
"NASA turns down UA asteroid plan Proposal to collect, return material was one of three project finalists
Eric Swedlund
Arizona Daily Star
14 December 2007
Link: NASA Discovery Program announcement about the lunar Gravity Recovery and Interior Laboratory (GRAIL) mission
The University of Arizona has lost out on $425 million in NASA funding after the space agency selected a competing proposal for its next Discovery Class mission.
The UA's OSIRIS mission, which would have launched a spacecraft to collect and return material from a near-Earth asteroid, was one of three finalists competing for the NASA funding. NASA officials announced this week that another finalist, a moon mission known as GRAIL, will move forward.
"It was a bit of a shock, frankly," said Michael Drake, director of the UA's Lunar and Planetary Laboratory and principal investigator for OSIRIS.
The lab will continue to seek funding for the asteroid-sample-return mission, modifying the proposal based on feedback from NASA officials. The ongoing Discovery program aims to launch a mission every 12 to 24 months.
Link: Article
"NASA turns down UA asteroid plan Proposal to collect, return material was one of three project finalists
Eric Swedlund
Arizona Daily Star
14 December 2007
Link: NASA Discovery Program announcement about the lunar Gravity Recovery and Interior Laboratory (GRAIL) mission
10 December 2007
Update on Results for Planetary Society's Apophis Mission Design Competition
I talked to Bruce Betts, Director of Projects for the Planetary Society, at the recent Space Investment Summit (SIS) 3 in San Jose, California. He said that the judging of their Apophis Mission Design Competition is taking a little longer. Whereas the original schedule called for winners to be announced in the middle of December, he stated that the current plan calls for an announcement in January 2008.
Article: "Practice run [to asteroid] before Mars suggested"
From the article:
"A near-Earth asteroid is a great intermediate destination that would allow NASA to check out the launch systems and crew vehicles, as well as set procedures," Huntress [former NASA associate administrator for science] told a group of about 100 people at the U.S. Space & Rocket Center. "It would be a six-month, or even a year mission, but that's quick compared to a three-year or longer human voyage to Mars...In the end it would give NASA confidence to go to another planet."
"Practice run before Mars suggested"
08 December 2007
Huntsville Times
Shelby G. Spires
Link: Article
"A near-Earth asteroid is a great intermediate destination that would allow NASA to check out the launch systems and crew vehicles, as well as set procedures," Huntress [former NASA associate administrator for science] told a group of about 100 people at the U.S. Space & Rocket Center. "It would be a six-month, or even a year mission, but that's quick compared to a three-year or longer human voyage to Mars...In the end it would give NASA confidence to go to another planet."
"Practice run before Mars suggested"
08 December 2007
Huntsville Times
Shelby G. Spires
Link: Article
Article: "The Best Way to Deflect an Asteroid"
From the article:
Massimiliano Vasile, a lecturer in aerospace engineering at the University of Glasgow, recently concluded a two-year study comparing nine asteroid-deflection methods, rating them for efficiency, complexity and launch readiness.
The best method, called “mirror bees,” entails sending a group of small satellites equipped with mirrors 30 to 100 feet wide into space to “swarm” around an asteroid and trail it, Vasile explains. The mirrors would be tilted to reflect sunlight onto the asteroid, vaporizing one spot and releasing a stream of gases that would slowly move it off course. Vasile says this method is especially appealing because it could be scaled easily: 25 to 5,000 satellites could be used, depending on the size of the rock.
The losing ideas — satellites equipped with lasers; detonating a nuclear explosion; pushing the asteroid with a spacecraft, to name a few — might still have their place. Vasile says improved technologies could make others appealing in the future. (In March, NASA released a report on “near Earth objects” that deemed the nuclear-explosion method the most effective.)
"The Best Way to Deflect an Asteroid"
New York Times
Lia Miller
09 December 2007
Link: Article
27 November 2007
"Return of the Falcon," a new animation of the Hayabusa mission
From Planetary Society Blog:
"JAXA has released a 30-minute video of the Hayabusa mission, "Return of the Falcon," combining computer animation with actual footage of the construction and launch as well as images from the spacecraft of Itokawa. It takes a while to download but is worth a watch. The video is set to the smooth jazz sounds of Emiko Kai, composed before the launch of Hayabusa (then named MUSES-C) to express "people's interest, hope, and support for a successful flight. The music represents the hopes of all people supporting the mission as though it represented a Muse gently watching over the challenges of a boy named 'Hayabusa.'"
Link: Planetary Society Blog Post
Link: JAXA Movie Link
"JAXA has released a 30-minute video of the Hayabusa mission, "Return of the Falcon," combining computer animation with actual footage of the construction and launch as well as images from the spacecraft of Itokawa. It takes a while to download but is worth a watch. The video is set to the smooth jazz sounds of Emiko Kai, composed before the launch of Hayabusa (then named MUSES-C) to express "people's interest, hope, and support for a successful flight. The music represents the hopes of all people supporting the mission as though it represented a Muse gently watching over the challenges of a boy named 'Hayabusa.'"
Link: Planetary Society Blog Post
Link: JAXA Movie Link
20 November 2007
NASA Article: "Hubble Zooms in on Heart of Mystery Comet"
Image above: Images of Comet 17P/Holmes as seen from the ground (left) and the Hubble Space Telescope (right). Click image for enlargement. Credit: A. Dyer, Alberta, Canada (left); NASA/ESA/H. Weaver/The Johns Hopkins University Applied Physics Laboratory (right)
From the new release:
NASA's Hubble Space Telescope has probed the bright core of Comet 17P/Holmes, which, to the delight of sky watchers, mysteriously brightened by nearly a millionfold in a 24-hour period beginning Oct. 23, 2007.
Astronomers used Hubble's powerful resolution to study Comet Holmes' core for clues about how the comet brightened. The orbiting observatory's Wide Field Planetary Camera 2 (WFPC2) monitored the comet for several days, snapping images on Oct. 29, Oct. 31, and Nov. 4. Hubble's crisp "eye" can see objects as small as 33 miles (54 kilometers) across, providing the sharpest most detailed view yet of the source of the spectacular brightening.
The Hubble image at right, taken Nov. 4, shows the heart of the comet. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust along lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a "bow tie" appearance.
The composite color image at left, taken Nov. 1 by an amateur astronomer, shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet's right side.
Link: NASA Press Release
Link: HubbelSite
Presentations from Recent Space Resources Space Resources Roundtable IX on Asteroids
The Ninth Space Resources Roundtable was held at the Colorado School of Mines from 24-27 October 2007. Many of the presentations dealt with In-Situ Resource Utilization (ISRU) on the moon and Mars. A few paper dealt with non-lunar ISRU (with some relation to asteroids). Here are some of the papers:
"Meteoric Steel as a Construction Resource on Mars"
G.A. Landis
Link: Presentation (zip file download, 5.9 MB)
"The Effective Bullet Shape for Impact Asteroid Sampling"
T. Makabe, H.Yano
Link: Presentation (zip file download, 6.5 MB)
"Defining Intercept Orbits for NEO 2004 GU0 in Support of Potential Long-Duration Manned or Sample-Return Missions"
J.G. Rodriguez
Link: Presentation (zip file download, 0.6 MB)
"ISRU Mission Recommendations to the SELENE-2 Project"
H. Kanamori
Link: Presentation (zip file download, 5.2 MB)
Link: Agenda (with Presentations)
"Meteoric Steel as a Construction Resource on Mars"
G.A. Landis
Link: Presentation (zip file download, 5.9 MB)
"The Effective Bullet Shape for Impact Asteroid Sampling"
T. Makabe, H.Yano
Link: Presentation (zip file download, 6.5 MB)
"Defining Intercept Orbits for NEO 2004 GU0 in Support of Potential Long-Duration Manned or Sample-Return Missions"
J.G. Rodriguez
Link: Presentation (zip file download, 0.6 MB)
"ISRU Mission Recommendations to the SELENE-2 Project"
H. Kanamori
Link: Presentation (zip file download, 5.2 MB)
Link: Agenda (with Presentations)
NYTimes Article on Arecibo: "A Hazy Future for a ‘Jewel’ of Space Instruments"
From the article...
With a quarter of its annual budget slashed, to $8 million from $10.5 million, Arecibo will be listening to the universe less often in the coming years. For researchers like Dr. Lovell, a professor of astronomy at Agnes Scott College in Georgia, that may mean her work — detecting radio waves emitted by ions from busted-up water molecules — will take years longer to complete.
More alarming would be the closing of Arecibo in four years, a possibility that has been raised by the National Science Foundation, which pays for the operation of the telescope.
In an era of tight and tightening budgets, a review panel for the foundation’s astronomy division two years ago looked for places where money could be freed up for new facilities. It recommended a 25 percent cut in Arecibo’s foundation financing by 2011 and then another 50 percent cut, to $4 million, in 2011.
The panel said Arecibo should look to other institutions and agencies to make up for the 2011 cut; if it could not find the money, the panel said, the foundation should consider closing it.
A quarter of its staff was laid off last year. The telescope is now on hiatus for repainting, but when it resumes operation, the number of observing hours will be cut, and nearly half of its receivers will be furloughed. Its emphasis will shift to large, continuing surveys, and smaller projects like Dr. Lovell’s may be much more squeezed than in the past.
An outcry followed the review panel’s decision, particularly from planetary scientists who thought that the group had overlooked Arecibo’s role in cataloging potential dangers from asteroids. Its radar can precisely plot the orbit of an asteroid to determine if it could be on course for a collision with Earth.
Two weeks ago, scientists and officials testified before a Congressional committee about the asteroid issue and touched on Arecibo’s fate. “The planetary science community is in danger of losing one of its instrumental crown jewels,” Donald K. Yeomans, a scientist at NASA’s Jet Propulsion Laboratory, told the House subcommittee on space and aeronautics.
NASA is a candidate to pick up some of the financing, particularly the $1 million to $2 million annual cost of the planetary radar. The agency has contributed to the radar operations in the past, as much as $500,000, but NASA officials say their focus should be on instruments in space, not on the ground.
"A Hazy Future for a ‘Jewel’ of Space Instruments"
Kenneth Chang
New York Times
20 November 2007
Link: Article
With a quarter of its annual budget slashed, to $8 million from $10.5 million, Arecibo will be listening to the universe less often in the coming years. For researchers like Dr. Lovell, a professor of astronomy at Agnes Scott College in Georgia, that may mean her work — detecting radio waves emitted by ions from busted-up water molecules — will take years longer to complete.
More alarming would be the closing of Arecibo in four years, a possibility that has been raised by the National Science Foundation, which pays for the operation of the telescope.
In an era of tight and tightening budgets, a review panel for the foundation’s astronomy division two years ago looked for places where money could be freed up for new facilities. It recommended a 25 percent cut in Arecibo’s foundation financing by 2011 and then another 50 percent cut, to $4 million, in 2011.
The panel said Arecibo should look to other institutions and agencies to make up for the 2011 cut; if it could not find the money, the panel said, the foundation should consider closing it.
A quarter of its staff was laid off last year. The telescope is now on hiatus for repainting, but when it resumes operation, the number of observing hours will be cut, and nearly half of its receivers will be furloughed. Its emphasis will shift to large, continuing surveys, and smaller projects like Dr. Lovell’s may be much more squeezed than in the past.
An outcry followed the review panel’s decision, particularly from planetary scientists who thought that the group had overlooked Arecibo’s role in cataloging potential dangers from asteroids. Its radar can precisely plot the orbit of an asteroid to determine if it could be on course for a collision with Earth.
Two weeks ago, scientists and officials testified before a Congressional committee about the asteroid issue and touched on Arecibo’s fate. “The planetary science community is in danger of losing one of its instrumental crown jewels,” Donald K. Yeomans, a scientist at NASA’s Jet Propulsion Laboratory, told the House subcommittee on space and aeronautics.
NASA is a candidate to pick up some of the financing, particularly the $1 million to $2 million annual cost of the planetary radar. The agency has contributed to the radar operations in the past, as much as $500,000, but NASA officials say their focus should be on instruments in space, not on the ground.
"A Hazy Future for a ‘Jewel’ of Space Instruments"
Kenneth Chang
New York Times
20 November 2007
Link: Article
19 November 2007
Interesting Asteroid/Comet Abstracts from Seventh IAA International Conference on Low-Cost Planetary Missions
Here are some interesting abstracts from the recent Seventh IAA International Conference on Low-Cost Planetary Missions (12-14 September, 2007, Pasadena, California USA).
- An Approach To Minimum Cost NEO Characterization. R. Reinert , R. Dissly, and Scott Mitchell, Ball Aerospace & Technologies Corp.
Link: Abstract
This abstract details a few mission concepts including (from the abstract):
- NEO Scout Low-Cost Spacecraft Concept. The NEO Scout mission concept is designed to minimize mission cost by using a very low-cost spacecraft. The NEO Scout approach uses a basic single-string architecture and a simple hydrazine monopropellant propulsion approach to rendezvous with a single NEO after a launch to a C3 of 5-10 by a Taurus, Falcon-5, or Minotaur-V medium-cost LV.
- NEO Sentry Minimum Launch Cost Mission Concept. The NEO Sentry mission is aimed at minimizing mission cost by using the lowest cost launch vehicle. It uses a high performance dual-mode bipropellant propulsion approach and ultra-low mass to rendezvous with a single NEO after launch to a 185-km LEO by a bargain-basement Falcon-1 LV.
- NEO Explorer (NEOX) Solar Electric Propelled Spacecraft Concept. The NEOX mission concept minimizes mission cost by enabling a single spacecraft to rendezvous with multiple NEO’s and by allowing multiple S/C to be launched by a single LV. The NEOX mission profile takes advantage of the low-thrust mission designs described below to rendezvous with up to three separate NEO's, or to perform a single rendezvous with a NEO inaccessible to chemically propelled vehicles. SEP efficiency lowers the NEOX S/C mass sufficiently to allow 2 such S/C to be launched on a single Delta-II, or four to be launched on the smallest Delta
- Deep Interior: Radar Exploration of Asteroid Interiors. A. Safaeinili (1), E. Asphaug (2), Y. Gim (1), E. Heggy (2), 1.Jet Propulsion Laboratory, 2. UC Santa Cruz, 3. Lunar and Planetary Institute
Link: Abstract
From the abstract...
Our nominal mission design for a radar investigation at a typical km-sized asteroid utilizes a polar orbit, with a period of weeks, while the asteroid spins underneath with a period of hours. The result is to "peel the apple" with thousands of unique radar returns providing global coverage at the spatial requirements of tomographic reconstruction. Another alternative, appealing at small (sub-km) asteroids where orbiting can be a challenge (solar wind pressure becomes comparable to the asteroid gravity), or at binary asteroid systems, is to utilize a hovering mission approach (as was done by the Japanese Hayabusa mission) while, as before, the asteroid spins underneath. Optical imaging is sufficient for the a posteriori reconstruction of spacecraft position at the time of data acquisition, so the only instruments required for this mission is the radar hardware, the antenna, and a simple camera. At present, this mission fits inside of the Discovery cost parameters even if one flies to two or more asteroids. With further radar flight heritage, this radar reflection imaging technology can evolve into a very low cost mission that could be flown routinely to near-Earth objects and other small bodies.
- Triple F: A comet nucleus sample return mission for ESA’s Cosmic Vision program. M. KÜPPERS1, H. U. KELLER1, E. KÜHRT2, P. EHRENFREUND3 AND THE TRIPLE F TEAM, 1 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, 2 Institut für Planetenforschung, DLR, Germany, 3 Leiden Institute of Chemistry, Leiden, The Netherlands
Link: Abstract
From the abstract...
A relatively small spacecraft will be launched into its interplanetary trajectory to a short period comet. After a short monitoring period near the cometary nucleus, needed to find suitable sampling spots, the spacecraft will touch down on the surface of the nucleus to collect samples. The sampling depth will be several decimeters. Finally the cooled samples will be returned to Earth. The mission is proposed to ESA’s Cosmic Vision and exploration programs, in co-operation with the Russian space agency.
- Hayabusa-2, The Next Asteroid Sample Return Mission of Japan. Makoto Yoshikawa, Hajime Yano, Junichiro Kawaguchi, Post-Hayabusa Mission WG, Japan Aerospace Exploration Agency.
Link: Abstract
From the abstract...
We have been considering post Hayabusa missions much before Hayabusa's arrival to the asteroid. This is because we think that asteroid is the key object to understand the origin and evolution of the solar system. Since the results of Hayabusa were very impressive and important from the point of the planetary science, we are now attempting to start next mission as soon as possible. We call the next mission as Hayabusa-2. The spacecraft is basically the same as Hayabusa. Of course we modify several points where there were problems. But the model is almost same, so we can save time to manufacture it, and we are hoping that we can launch it in 2011 or 2012. The target is again small near earth asteroid but C-type. So we are looking forward to seeing how the small C-type asteroid looks like. The current target of Hayabusa-2 is 1999 JU3.
Also, we are considering another sample return mission, which we call "Hayabusa-Mark2" tentatively. Hayabusa-Mark2 is not the copy of Hayabusa, but it is much-advanced mission both in the sampling and the remote sensing. For example, we want to challenge sampling with preserving depth profile and to get much more detailed data of the sampling sight. Hayabusa-Mark2 is also considered in the scheme of Cosmic Vision of ESA.
- Stand-off Estimation of Binary Asteroid Mass Distributions. D.J. Scheeres1,2 and E.G. Fahnestock1, 1The University of Michigan, Ann Arbor.
Link: Abstract
From the abstract...
Recent investigations of the dynamics and morphology of the binary asteroid system 1999 KW4 have revealed a complex and dynamic system that should be typical of binary asteroids. While investigation of the KW4 system is of intrinsic interest, methods we have developed to understand and characterize this system are also applicable to other NEA binaries with similar morphology. In this presentation we will detail an underlying dynamical theory we have developed and an accompanying procedure which allows one to estimate the mass distribution properties of a binary system without having to fly a spacecraft within the gravitational field of the system. Specifically, we show that in a system such as KW4 there is sufficient information in the dynamical oscillation of its components to estimate the second degree and order gravity field coefficients and moments of inertia of both bodies based on stand-off observations alone. This is significant when compared to the situation for solitary asteroids where the gravity field can only be determined by tracking the motion of a spacecraft perturbed by the higher order gravity coefficients. Also, the moments of inertia cannot be estimated for solitary asteroids, except if the body is in non-uniform rotation. For a binary system with an excitation level similar to KW4’s, it is possible to determine the total mass, mass fraction of the system, the J2 gravity coefficient of the primary, the principal moments of inertia of the secondary, and potentially the principal moments of inertia of the primary if it has a significant equatorial ellipticity. The moments of inertia contain significant information on how the mass is distributed within a body not available from the gravity coefficients alone. The placement of passive probes on the surface of the binary components with radio transmitters can yield significantly improved precision for these estimated quantities. The estimation of these quantities do not require the spacecraft to orbit the system closely, which can reduce a mission’s operational costs significantly.
Link: 7th Low-Cost Planetary Missions Conference Website
Link: 7th Low-Cost Planetary Missions Conference Website: Agenda
- An Approach To Minimum Cost NEO Characterization. R. Reinert , R. Dissly, and Scott Mitchell, Ball Aerospace & Technologies Corp.
Link: Abstract
This abstract details a few mission concepts including (from the abstract):
- NEO Scout Low-Cost Spacecraft Concept. The NEO Scout mission concept is designed to minimize mission cost by using a very low-cost spacecraft. The NEO Scout approach uses a basic single-string architecture and a simple hydrazine monopropellant propulsion approach to rendezvous with a single NEO after a launch to a C3 of 5-10 by a Taurus, Falcon-5, or Minotaur-V medium-cost LV.
- NEO Sentry Minimum Launch Cost Mission Concept. The NEO Sentry mission is aimed at minimizing mission cost by using the lowest cost launch vehicle. It uses a high performance dual-mode bipropellant propulsion approach and ultra-low mass to rendezvous with a single NEO after launch to a 185-km LEO by a bargain-basement Falcon-1 LV.
- NEO Explorer (NEOX) Solar Electric Propelled Spacecraft Concept. The NEOX mission concept minimizes mission cost by enabling a single spacecraft to rendezvous with multiple NEO’s and by allowing multiple S/C to be launched by a single LV. The NEOX mission profile takes advantage of the low-thrust mission designs described below to rendezvous with up to three separate NEO's, or to perform a single rendezvous with a NEO inaccessible to chemically propelled vehicles. SEP efficiency lowers the NEOX S/C mass sufficiently to allow 2 such S/C to be launched on a single Delta-II, or four to be launched on the smallest Delta
- Deep Interior: Radar Exploration of Asteroid Interiors. A. Safaeinili (1), E. Asphaug (2), Y. Gim (1), E. Heggy (2), 1.Jet Propulsion Laboratory, 2. UC Santa Cruz, 3. Lunar and Planetary Institute
Link: Abstract
From the abstract...
Our nominal mission design for a radar investigation at a typical km-sized asteroid utilizes a polar orbit, with a period of weeks, while the asteroid spins underneath with a period of hours. The result is to "peel the apple" with thousands of unique radar returns providing global coverage at the spatial requirements of tomographic reconstruction. Another alternative, appealing at small (sub-km) asteroids where orbiting can be a challenge (solar wind pressure becomes comparable to the asteroid gravity), or at binary asteroid systems, is to utilize a hovering mission approach (as was done by the Japanese Hayabusa mission) while, as before, the asteroid spins underneath. Optical imaging is sufficient for the a posteriori reconstruction of spacecraft position at the time of data acquisition, so the only instruments required for this mission is the radar hardware, the antenna, and a simple camera. At present, this mission fits inside of the Discovery cost parameters even if one flies to two or more asteroids. With further radar flight heritage, this radar reflection imaging technology can evolve into a very low cost mission that could be flown routinely to near-Earth objects and other small bodies.
- Triple F: A comet nucleus sample return mission for ESA’s Cosmic Vision program. M. KÜPPERS1, H. U. KELLER1, E. KÜHRT2, P. EHRENFREUND3 AND THE TRIPLE F TEAM, 1 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, 2 Institut für Planetenforschung, DLR, Germany, 3 Leiden Institute of Chemistry, Leiden, The Netherlands
Link: Abstract
From the abstract...
A relatively small spacecraft will be launched into its interplanetary trajectory to a short period comet. After a short monitoring period near the cometary nucleus, needed to find suitable sampling spots, the spacecraft will touch down on the surface of the nucleus to collect samples. The sampling depth will be several decimeters. Finally the cooled samples will be returned to Earth. The mission is proposed to ESA’s Cosmic Vision and exploration programs, in co-operation with the Russian space agency.
- Hayabusa-2, The Next Asteroid Sample Return Mission of Japan. Makoto Yoshikawa, Hajime Yano, Junichiro Kawaguchi, Post-Hayabusa Mission WG, Japan Aerospace Exploration Agency.
Link: Abstract
From the abstract...
We have been considering post Hayabusa missions much before Hayabusa's arrival to the asteroid. This is because we think that asteroid is the key object to understand the origin and evolution of the solar system. Since the results of Hayabusa were very impressive and important from the point of the planetary science, we are now attempting to start next mission as soon as possible. We call the next mission as Hayabusa-2. The spacecraft is basically the same as Hayabusa. Of course we modify several points where there were problems. But the model is almost same, so we can save time to manufacture it, and we are hoping that we can launch it in 2011 or 2012. The target is again small near earth asteroid but C-type. So we are looking forward to seeing how the small C-type asteroid looks like. The current target of Hayabusa-2 is 1999 JU3.
Also, we are considering another sample return mission, which we call "Hayabusa-Mark2" tentatively. Hayabusa-Mark2 is not the copy of Hayabusa, but it is much-advanced mission both in the sampling and the remote sensing. For example, we want to challenge sampling with preserving depth profile and to get much more detailed data of the sampling sight. Hayabusa-Mark2 is also considered in the scheme of Cosmic Vision of ESA.
- Stand-off Estimation of Binary Asteroid Mass Distributions. D.J. Scheeres1,2 and E.G. Fahnestock1, 1The University of Michigan, Ann Arbor.
Link: Abstract
From the abstract...
Recent investigations of the dynamics and morphology of the binary asteroid system 1999 KW4 have revealed a complex and dynamic system that should be typical of binary asteroids. While investigation of the KW4 system is of intrinsic interest, methods we have developed to understand and characterize this system are also applicable to other NEA binaries with similar morphology. In this presentation we will detail an underlying dynamical theory we have developed and an accompanying procedure which allows one to estimate the mass distribution properties of a binary system without having to fly a spacecraft within the gravitational field of the system. Specifically, we show that in a system such as KW4 there is sufficient information in the dynamical oscillation of its components to estimate the second degree and order gravity field coefficients and moments of inertia of both bodies based on stand-off observations alone. This is significant when compared to the situation for solitary asteroids where the gravity field can only be determined by tracking the motion of a spacecraft perturbed by the higher order gravity coefficients. Also, the moments of inertia cannot be estimated for solitary asteroids, except if the body is in non-uniform rotation. For a binary system with an excitation level similar to KW4’s, it is possible to determine the total mass, mass fraction of the system, the J2 gravity coefficient of the primary, the principal moments of inertia of the secondary, and potentially the principal moments of inertia of the primary if it has a significant equatorial ellipticity. The moments of inertia contain significant information on how the mass is distributed within a body not available from the gravity coefficients alone. The placement of passive probes on the surface of the binary components with radio transmitters can yield significantly improved precision for these estimated quantities. The estimation of these quantities do not require the spacecraft to orbit the system closely, which can reduce a mission’s operational costs significantly.
Link: 7th Low-Cost Planetary Missions Conference Website
Link: 7th Low-Cost Planetary Missions Conference Website: Agenda
ESPA Ring as Foundation for Future Spacecraft Design
I have been recently interested in the use of the ESPA ring for planetary missions (potentially including asteroid missions). The most recent NASA Small Business Innovation Research (SBIR) grants included one to CSA engineering for examination of the ESPA ring for future planetary missions (see below).
NASA 2007 Phase I SBIR: "ESPA for Lunar and Science Missions"
NASA mission planning in the next decade includes small spacecraft and secondary flight opportunities on Evolved Expendable Launch Vehicles (EELVs), specifically Atlas V and Delta IV. NASA's use of EELVs is accelerated because of the impending termination of the Delta II launcher. Nearly all EELVs slated for launch have significant excess payload capacity. The EELV Secondary Payload Adapter (ESPA) Ring was developed by CSA Engineering under an Air Force SBIR to utilize excess lift capability by providing a secondary mission capability.
ESPA, as built, can provide access to space for NASA lunar and science missions. However, to ensure that diverse NASA mission objectives can be achieved with the best possible mission configurations, structural tailoring of the ESPA will be required. The proposed effort will develop modular features of ESPA that are required for optimal NASA mission configurations targeting, but not necessarily limited to, the following:
(1) Separable ESPA: Separation capability built into the ESPA Ring.
(2) Hierarchical ESPA: Scaling of the ESPA design for larger EELV payloads and for small launch vehicles.
(3) ESPA Mounts: Interior and exterior mounting for spacecraft and auxiliary structures.
Phase 1 will establish feasibility for the modular ESPA designs. Plans will be presented for flight qualification of all designs. Phase 2 will produce flight qualified hardware to at least TRL 6 for a design determined to be the most desirable for near-term NASA implementation.
Link: NASA 2007 Phase I SBIR Announcement for CSA Engineering Inc.
Link: ESPA ring paper - "Designing for ESPA: The Challenges of Designing a Spacecraft for a Launch Accommodation Still in Development"
Link: AeroAstro ESPA-class concepts
Link: ESPA ring brochure from CSA Engineering (PDF)
Link: NASA Lunar CRater Observation and Sensing Satellite (LCROSS) spacecraft (based upon ESPA ring), part of the Lunar Reconnaissance Orbiter (LRO)
NASA 2007 Phase I SBIR: "ESPA for Lunar and Science Missions"
NASA mission planning in the next decade includes small spacecraft and secondary flight opportunities on Evolved Expendable Launch Vehicles (EELVs), specifically Atlas V and Delta IV. NASA's use of EELVs is accelerated because of the impending termination of the Delta II launcher. Nearly all EELVs slated for launch have significant excess payload capacity. The EELV Secondary Payload Adapter (ESPA) Ring was developed by CSA Engineering under an Air Force SBIR to utilize excess lift capability by providing a secondary mission capability.
ESPA, as built, can provide access to space for NASA lunar and science missions. However, to ensure that diverse NASA mission objectives can be achieved with the best possible mission configurations, structural tailoring of the ESPA will be required. The proposed effort will develop modular features of ESPA that are required for optimal NASA mission configurations targeting, but not necessarily limited to, the following:
(1) Separable ESPA: Separation capability built into the ESPA Ring.
(2) Hierarchical ESPA: Scaling of the ESPA design for larger EELV payloads and for small launch vehicles.
(3) ESPA Mounts: Interior and exterior mounting for spacecraft and auxiliary structures.
Phase 1 will establish feasibility for the modular ESPA designs. Plans will be presented for flight qualification of all designs. Phase 2 will produce flight qualified hardware to at least TRL 6 for a design determined to be the most desirable for near-term NASA implementation.
Link: NASA 2007 Phase I SBIR Announcement for CSA Engineering Inc.
Link: ESPA ring paper - "Designing for ESPA: The Challenges of Designing a Spacecraft for a Launch Accommodation Still in Development"
Link: AeroAstro ESPA-class concepts
Link: ESPA ring brochure from CSA Engineering (PDF)
Link: NASA Lunar CRater Observation and Sensing Satellite (LCROSS) spacecraft (based upon ESPA ring), part of the Lunar Reconnaissance Orbiter (LRO)
18 November 2007
Asteroid 2007 VF189: Son of ROSETTA
Selection from the Planetary Society blog entry...
On the heels of the news last week that the Rosetta spacecraft was spotted by sky surveys and briefly named among the minor planets as 2007 VN84 came another close approach by a newly discovered near-Earth object, designated 2007 VF189, which had an orbit surprisingly similar to the Rosetta spacecraft, making a close approach to Earth (closer than the Moon, about 250,000 kilometers away) roughly six hours after Rosetta, on November 14. This is a story that has been unfolding on the Minor Planets Mailing List, and I've been watching it with interest. (A big thanks to all of the various MPML participants whose comments I'm paraphrasing below, in particular Richard Kowalski -- whose Catalina Sky Survey discovered both 2007 VN84 and 2007 VF189 -- as well as Steven Chesley and Alan Harris.)
In brief: the probability for there to be a random object so close in the sky to Rosetta is 1 in 70; the probability for Rosetta and this object to come close to Earth within 6 hours of each other is 1 in 10; and the probability that they would have velocities within 2.1 km/sec of each other is 1 in 10. Multiplying those together, you get a 1 in 7000 chance for Rosetta and another object to pass so close to each other, at nearly the same speed, near Earth. That's an interesting number, because it's not too likely, but neither is it vanishingly unlikely. Plenty of people bet lots of money on worse odds.
In the end, then, 2007 VF189 is a small, unremarkable Apollo-class object (meaning it's an Earth-orbit-crossing asteroid with an orbital period of longer than one year), and nobody would have paid much attention to it if not for last week's mixup.
"Son of Rosetta"
The Planetary Society Weblog
By Emily Lakdawalla
16 November 2007
Link: Article
Link: JPL Small-Body Database Browser for 2007 VF189
Link: Minor Planet Center data for 2007 VF189
Link: Article from Der Spiegel, Thorsten Dambeck, 15 November 2007, "Unknown flying object pursues space probe "Rosetta"
Link: Translation of Above Der Spiegel Article
On the heels of the news last week that the Rosetta spacecraft was spotted by sky surveys and briefly named among the minor planets as 2007 VN84 came another close approach by a newly discovered near-Earth object, designated 2007 VF189, which had an orbit surprisingly similar to the Rosetta spacecraft, making a close approach to Earth (closer than the Moon, about 250,000 kilometers away) roughly six hours after Rosetta, on November 14. This is a story that has been unfolding on the Minor Planets Mailing List, and I've been watching it with interest. (A big thanks to all of the various MPML participants whose comments I'm paraphrasing below, in particular Richard Kowalski -- whose Catalina Sky Survey discovered both 2007 VN84 and 2007 VF189 -- as well as Steven Chesley and Alan Harris.)
In brief: the probability for there to be a random object so close in the sky to Rosetta is 1 in 70; the probability for Rosetta and this object to come close to Earth within 6 hours of each other is 1 in 10; and the probability that they would have velocities within 2.1 km/sec of each other is 1 in 10. Multiplying those together, you get a 1 in 7000 chance for Rosetta and another object to pass so close to each other, at nearly the same speed, near Earth. That's an interesting number, because it's not too likely, but neither is it vanishingly unlikely. Plenty of people bet lots of money on worse odds.
In the end, then, 2007 VF189 is a small, unremarkable Apollo-class object (meaning it's an Earth-orbit-crossing asteroid with an orbital period of longer than one year), and nobody would have paid much attention to it if not for last week's mixup.
"Son of Rosetta"
The Planetary Society Weblog
By Emily Lakdawalla
16 November 2007
Link: Article
Link: JPL Small-Body Database Browser for 2007 VF189
Link: Minor Planet Center data for 2007 VF189
Link: Article from Der Spiegel, Thorsten Dambeck, 15 November 2007, "Unknown flying object pursues space probe "Rosetta"
Link: Translation of Above Der Spiegel Article
16 November 2007
Interesting Article on Modern Perception of Global Natural Risks
Selections from the article...
In recent years, humankind has become aware of a number of global and existential risks that potentially threaten our survival.
These natural and man-made risks comprise cosmic disasters, volcanic super-eruptions and climatic disruption on the one hand, and nuclear warfare, technological catastrophes and fully-fledged bioterrorism on the other.
In order to secure the future of civilisation, we are challenged to recognise and ward off these low-probability, but potentially destructive hazards.
A new debate is gaining momentum about how best to achieve a secure future for our planetary civilisation.
A recent study confirms that the annual percentage of people killed by natural disasters has decreased tenfold in the last 40 years, in spite of the fact that the average annual number of recorded disasters increased fivefold. Evidently, open and technological societies are becoming increasingly resilient to the effects of natural disasters.
The more people see, hear or read about the risks of Near Earth Object (NEO) impacts, nuclear terrorism or global climate catastrophes, the more concerned they have become. The mere mention of catastrophic risks, regardless of its low probability, is enough to make the danger more urgent, thus increasing public estimates of danger.
Scientists who evaluate risks are often torn between employing level-headed risk communication and the temptation to overstate potential danger.
In recent years, leading scientists in the UK, such as Brandon Carter, Stephen Hawking and Sir Martin Rees, have advanced the so-called Doomsday Argument, a cosmological theory in which global catastrophes due to low-probability mega-disasters play a considerable role.
This speculative theory maintains that scientific risk assessments have systematically underestimated existential hazards. Hence the probability is growing that humankind will be wiped out in the near future.
Nevertheless, there are many good and compelling reasons why human extinction is not predetermined or unavoidable.
According to a more optimistic view of the future, all existential risks can be tackled, eliminated or significantly reduced through the application of human ingenuity, hyper-technologies and global democratisation.
Current advances in developing an effective planetary defence system, for example, will eventually lead to a protective shield that can safeguard life on the Earth from disastrous NEO impacts.
"Existential risk and democratic peace"
BBC Viewpoint
Benny Peiser, Liverpool John Moores University, UK
15 November 2007
Link: Article
In recent years, humankind has become aware of a number of global and existential risks that potentially threaten our survival.
These natural and man-made risks comprise cosmic disasters, volcanic super-eruptions and climatic disruption on the one hand, and nuclear warfare, technological catastrophes and fully-fledged bioterrorism on the other.
In order to secure the future of civilisation, we are challenged to recognise and ward off these low-probability, but potentially destructive hazards.
A new debate is gaining momentum about how best to achieve a secure future for our planetary civilisation.
A recent study confirms that the annual percentage of people killed by natural disasters has decreased tenfold in the last 40 years, in spite of the fact that the average annual number of recorded disasters increased fivefold. Evidently, open and technological societies are becoming increasingly resilient to the effects of natural disasters.
The more people see, hear or read about the risks of Near Earth Object (NEO) impacts, nuclear terrorism or global climate catastrophes, the more concerned they have become. The mere mention of catastrophic risks, regardless of its low probability, is enough to make the danger more urgent, thus increasing public estimates of danger.
Scientists who evaluate risks are often torn between employing level-headed risk communication and the temptation to overstate potential danger.
In recent years, leading scientists in the UK, such as Brandon Carter, Stephen Hawking and Sir Martin Rees, have advanced the so-called Doomsday Argument, a cosmological theory in which global catastrophes due to low-probability mega-disasters play a considerable role.
This speculative theory maintains that scientific risk assessments have systematically underestimated existential hazards. Hence the probability is growing that humankind will be wiped out in the near future.
Nevertheless, there are many good and compelling reasons why human extinction is not predetermined or unavoidable.
According to a more optimistic view of the future, all existential risks can be tackled, eliminated or significantly reduced through the application of human ingenuity, hyper-technologies and global democratisation.
Current advances in developing an effective planetary defence system, for example, will eventually lead to a protective shield that can safeguard life on the Earth from disastrous NEO impacts.
"Existential risk and democratic peace"
BBC Viewpoint
Benny Peiser, Liverpool John Moores University, UK
15 November 2007
Link: Article
15 November 2007
Articles on Mistaken Identification of ESA Rosetta Spacecraft as Asteroid
Image description: Rosetta’s navigation camera (NAVCAM) took this shot of Earth right after Rosetta’s closest approach to our planet. The picture was taken at 22:56 CET on 13 November, as Rosetta’s second Earth swing-by concluded, while the spacecraft was flying at a height of about 6250 km from the surface. Credits: ESA.
Image description: An artist's rendition of Rosetta's second close approach to Earth on Nov. 13, 2007. The swing-by is Rosetta's third major step on its 10-year journey to comet 67/P-Churyumov-Gerasimenko. Credit: C. Carreau/ESA.
From one of the articles...
The Minor Planet Center, the world clearinghouse for information about newly discovered asteroids, raised the alarm last week. In an email to professional observatories, they announced that a previously unknown asteroid would miss the Earth by just 5,600 kilometers.
The newly discovered space rock was given an official label by the MPC, which is run by the Smithsonian Astrophysical Observatory, Massachusetts, for the International Astronomical Union. Observations for 2007 VN84 were collected from astronomers around the world, to track the threatening celestial body. This would be one of the closest approaches ever by a sizable asteroid – its distance away being less than half the diameter of the Earth.
Then Denis Denisenko, of Moscow's Space Research Institute (IKI), made an interesting discovery. He noticed that the incoming asteroid's track matched that of the European space probe Rosetta on a scheduled flyby of Earth.
The Rosetta craft was launched from Europe's Guiana Space Center in early March of 2004; the purpose of the space probe is to place itself in low orbit around the comet Churyumov-Gerasimenko at a distance of 675 million kilometers from the sun. To get there, the billion-dollar craft will spend ten years boosting its velocity (using the gravity assist technique) with no fewer than three flybys of Earth and one of Mars.
Denisenko's discovery came none too soon; Britain's Royal Astronomical Society was preparing a bulletin for the media that would have been released on Monday.
"Near-Miss Asteroid Found to be Artificial"
Bill Christensen
Space.com
12 November 2007
Link: Article
From another article...
But the incident raises questions about how well the warning system works. The Minor Planet Center complains that, "this incident highlights the deplorable state of availability of positional information on distant artificial objects". This lack of a centralised database makes checking incoming objects against known space probes difficult.
"Astronomers defend asteroid warning mix-up"
Justin Mullins
NewScientist.com
13 November 2007
Link: Article
Article: "Incredible Comet [Comet 17P Holmes] Bigger than the Sun"
From the article...
A comet that has delighted backyard astronomers in recent weeks after an unexpected eruption has now grown larger than the sun...The sun remains by far the most massive object in the solar system, with an extended influence of particles that reaches all the planets. But the comparatively tiny Comet Holmes has released so much gas and dust that its extended atmosphere, or coma, appears larger than the diameter of the sun in a new image..."It continues to expand and is now the largest single object in the solar system," according to astronomers at the University of Hawaii.
"The coma's diameter on Nov. 9 was 869,900 miles (1.4 million kilometers), based on measurements by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. They used observations from the Canada-France-Hawaii Telescope. The sun's diameter, stated differently by various sources and usually rounded to the nearest 100, is about 864,900 miles (1.392 million kilometers)."
Incredible Comet Bigger than the Sun
Robert Roy Britt
Space.com
15 November 2007
Link: Article
12 November 2007
NEO News (11/12/07) More on Congress NEO Hearings
Note: The following is the 10/12/07 Edition of NEO News, an email newsletter distributed by David Morrison.
NEO News (11/12/07) More on Congress NEO Hearings
This edition of NEO News contains some additional material on the hearings held last week by the House Subcommittee on Space and Aeronautics dealing with advanced NEO searches and related topics. I have (1) posted a news story on the hearing from Physorg.com, (2) selected several very nice summary comments taken from the testimony, and (3) also added a few comments of my own on some misunderstandings that can arise in these discussions, misunderstandings that apparently caused the NASA NEO study to limit itself to technologies for deflecting NEAs between 140m and 1km in diameter, neglecting both the most dangerous (>1km) and the most common (<140m) cases. Also, unrelated to the hearings, there is (4) a post on the strange story off how the Rosetta spacecraft was mistaken for a NEA.
David Morrison
===================================
(1) NASA PRESSED TO AVERT CATASTROPHIC DEEP IMPACT
AFP, 8 November 2007
http://www.physorg.com/news113748841.html
NASA penny-pinching risks exposing humankind to a planetary catastrophe if a big enough asteroid evades detection and slams into Earth, US lawmakers argued Thursday. But the US space agency said the chances of a new "Near-Earth Object" (NEO) like the one that wiped out the dinosaurs were too remote to divert scarce resources.
Scott Pace, head of program analysis and evaluation at NASA, said the agency could not do more to detect NEOs "given the constrained resources and the strategic objectives NASA already has been tasked with."
Pace and other NASA officials were grilled at a congressional hearing on the existing NEO program, which seized the public imagination in the late 1990s through the movies "Armageddon" and "Deep Impact." Lawmakers decried the threatened closure of a giant radio telescope in Puerto Rico run with NASA's assistance that is the world's foremost facility for tracking space objects.
"We're talking about minimal expense compared to the cost of having to absorb this type of damage," Republican Congressman Dana Rohrabacher said. "After all, it may be the entire planet that is destroyed!"
Puerto Rico delegate Luis Fortuno fretted over the economic impact on his impoverished US territory, but also warned of the broader consequences for the entire planet. The National Science Foundation has earmarked the Arecibo Observatory, which featured in science-fiction movie "Contact" and the James Bond installment "Goldeneye," for closure after 2011 if new private-sector money is not found.
NASA officials said they would get by with new monitoring systems, including a network of four telescopes being built in Hawaii by the US Air Force.
Critics say NASA has imposed big cuts on many research programs in a bid to meet President George W. Bush's goal of returning astronauts to the Moon by 2020 and use it as a stepping stone for manned missions to Mars and beyond.
The hearing of the House of Representatives space and aeronautics subcommittee highlighted one small asteroid named Apophis, about 250 meters (273 yards) wide, which some scientists say could swing by Earth on Friday, April 13, 2029. NASA says there is a one in 45,000 chance that Apophis could pass through a "gravitational keyhole" and return to hit the planet in 2036. "It's a very unlikely situation and one we can drive to zero, probably," said Donald Yeomans, who manages the NEO program at NASA's Jet Propulsion Laboratory.
NASA now only tracks NEOs larger than one kilometer (0.62 miles) in diameter, which come near Earth only once every few hundred thousand years. Objects of that size can cause global disaster through their immediate surface impact and by triggering rapid climate change. "Extinction-class" objects measuring at least 10 kilometers, such as the object that crashed into Mexico's Yucatan peninsula about 65 million years ago, would be rarer still.
Lawmakers complained that NASA had failed to come up with a budget in line with a 2005 act of Congress that mandated an expanded search for NEOs that are at least 140 meters in diameter. The agency's annual NEO budget of 4.1 million dollars was attacked as being too meager to cover this goal.
There are about 20,000 smaller objects with the potential to hit home, according to NASA, and Republican Representative Tom Feeney said "they could still inflict large regional impacts if they struck the Earth."
Options to divert space rocks on a collision course with Earth include slamming nuclear missiles into them, although scientists believe that in most cases involving smaller debris, conventional rockets would do the job.
Yeomans said also that while the European and Japanese space agencies are stepping up their own NEO programs, more than 98 percent of the work is now done by NASA.
© 2007 AFP
==================================
(2) BRIEF KEY MESSAGES FROM THE NEO HEARING
From testimony of J. Anthony Tyson, LSST
Until recently, the discussion of risk associated with an impact of a NEO has been statistical; what is the probability? This is similar to considerations of risk in many other areas such as weather and traffic accidents. What if it were feasible to deploy a system that would alert me of an impending traffic accident well in advance? That would change the very nature of that risk from a probabilistic worry to a deterministic actionable situation. The ability to detect virtually every potentially hazardous Near-Earth object and determine its orbit with precision transforms that statistical threat into a deterministic prediction. We face many threats, and virtually all of them are either so complex or unpredictable that they are treated probabilistically even though the social and financial consequences are legion. With a comparatively small investment the NEO risk can be transformed from a probabilistic one to a deterministic one, enabling mitigation.
From testimony of Donald Yeomans, JPL
What should be done in the event of an identified NEO Threat? A number of existing technologies can deflect an Earth threatening asteroid -- if there is time. The primary goal of the PHA survey programs is to discover them early and provide the necessary time. An asteroid that is predicted to hit Earth might require a change in its velocity of only 3 millimeters per second if this impulse were applied twenty years in advance of the impact. The key to a successful deflection is having sufficient time to carry it out, whether it is the slow, gentle drag of a gravity tractor or a more impulsive shove from an impacting spacecraft or explosive device. In either case, a verification process would be required to ensure the deflection maneuver was successful and to ensure the object's subsequent motion would not put it on yet another Earth impacting trajectory. While suitable deflection technologies exist, none of them can be effective if we are taken by surprise. It is the aggressive survey efforts and robust planetary radars that must ensure that the vast majority of potentially hazardous objects are discovered and tracked well in advance of any Earth threatening encounters. The first three steps in any asteroid mitigation process are: Find them early, find them early, and find them early!
From testimony of Russell Schweickart, B612 Foundation
In closing I would suggest a personal perspective based on having spent the last 6 years of my life studying this issue. NEOs are part of nature. A NEO impact is a natural hazard in much the same way as are hurricanes, tsunamis, floods, etc. NEO impacts are deceptively infrequent, yet devastating at potentially unimaginable levels. NEOs are however not our enemies. We do not need to "defend" against NEOs, we need to protect ourselves from their occasional impact, as we do with other natural hazards.
Unlike other natural hazards, however, NEO impacts can be predicted well ahead of time and actually prevented from occurring. If we live up to our responsibility, if we wisely use our amazing technology, and if we are mature enough, as a nation and as a community of nations, there may never again be a substantially damaging asteroid impact on the Earth. We have the ability to make ourselves safe from cosmic extinction. If we cannot manage to meet this challenge, we will, in my opinion, have failed to meet our evolutionary responsibility.
==================================
SOME MISCONSEPTIONS ABOUT NEO IMPACTS
David Morrison
Some of the often misunderstood concepts behind NEO surveys concern the meaning of a specified 90% target size, 1km diameter in the case of the current Spaceguard Survey, and 140m for the proposed Spaceguard deep survey. An example from the news story above is this statement: "NASA now only tracks NEOs larger than one kilometer (0.62 miles) in diameter." But the fact is, in Al Harris's often-quoted words, "we don't throw back the small ones." The majority of NEAs found by Spaceguard are less than 1km in diameter. By the time we reach 90% completeness at 1km, we will have found almost ten times more NEAs smaller than this limit, and certainly these smaller NEAs are tracked and cataloged. The best known example is Apophis, the most dangerous NEA found yet, which is only about half the 1km Spaceguard target size. In any such survey, most of the NEAs will be below the index size, but these will be less complete than the index size used for the 90% metric.
Similarly, any survey scaled for 140m NEAs will predominantly find NEAs smaller than this size. In fact, the discoveries from this deep survey will extend down below the atmospheric cut-off at about 30m diameter. Rusty Schweickart in his testimony estimates that when we reach 90% completeness at 140m, we will be 40% complete for Tunguska-size objects. The most likely object to require deflection is actually below the 140m index size.
There are implications of these facts that need to be considered. For example, the data handling must be scaled for nearly 10 times the number of NEAs at 140m size, since again, we won't throw back the small ones. Further, any plans for deflection should recognize that the most likely challenges will come from NEAs less than 140m in diameter. The NASA study apparently focused only on deflecting NEAs between 140m and 1km in diameter, neglecting both the most dangerous (those larger than 1km, of which 10% will remain undiscovered at the nominal end of the current Spaceguard survey) and the most common (those under 140m diameter).
None of the prepared testimony explicitly mentioned uncertainties in the population of small NEAs or in the ability to model the efficiency of survey telescopes. This in understandable, given the limited time available, but it does over-emphasize specific dates and sizes that enter into models of the new deep surveys. It is not unreasonable that both the number of NEAs larger than 140m and the ability of new telescopes (both ground-based and space based) to detect and identify them could be off by as much as a factor of two. We won't know when we are likely to achieve 90% completeness at 140m until the telescopes are built and the new survey is well underway. Therefore I don't worry too much about small differences in the estimated dates of completion. I am more interested in the start date than the completion date for Spaceguard-2.
=================================
(4) THAT'S NO NEAR-EARTH OBJECT, IT'S A SPACESHIP
The Planetary Society Weblog, 9 November 2007
http://www.planetary.org/blog/article/00001227/
By Emily Lakdawalla
Whenever I am out at night with my husband and I point to the sky and say, "that's Venus" or "look, that's Saturn, see how yellow it is," he likes to burst my bubble by saying "no, it's just a plane." Every great once in a while, I'm sad to say, he's right.
Well, a similar scenario has just unfolded within the near-Earth asteroid community. On November 8 the Minor Planet Center issued a routine Minor Planet Electronic Circular, reporting on observations of a newly discovered object, newly designated 2007 VN84. Several observatories had spotted the faint object, and, based upon those observations, an orbital trajectory was calculated, which placed the object on a very close path by Earth, "0.000081 AU (1.89 Earth radii) on Nov 13.844 UT." Now, that 1.89 Earth radii is measured relative to Earth's center, meaning that the thing was going to fly within 6,000 kilometers of Earth on November 13 at 20:15 UTC. That's pretty close! This is a truly near-Earth object.
Rosetta's second Earth flyby is due to take place Closest approach will take place on 13 November 2007 at 20:57 UTC, at which time Rosetta will speed past at 45,000 km/h (about 12.5 km/s) relative to Earth. At this time, Rosetta will be 5,301 km above the Pacific Ocean, south-west of Chile, at 63° 46' south and 74° 35' west. But a sharp-eyed reader of the MPECs, Denis Denisenko, realized that there was something going on. I'm not sure what tipped him off; whether he noticed that specific date and time and remembered another significant event to happen on that day, or whether he has a habit of checking near-Earth object trajectories against catalogs of manmade objects. However the discovery happened, he realized that 2007 VN84 had a trajectory that was awfully similar to Rosetta, which is due to swing by Earth on November 13 at 20:57 UTC. He posted as much to the Minor Planet Mailing List.
Indeed, today, the Minor Planet Center issued an Editorial Notice stating that further investigation has shown that the object briefly designated 2007 VN84 is, in fact, the Rosetta spacecraft, and that the designation "2007 VN84" will be retired. The editorial notice goes on to say, with notable asperity, "This incident, along with previous NEOCP postings of the WMAP spacecraft, highlights the deplorable state of availability of positional information on distant artificial objects.... A single source for information on all distant artificial objects would be very desirable."
I think it's pretty funny that a very big spacecraft designed to study minor planets in the solar system has itself, however briefly, been named among the minor planets. This episode also goes to show how sensitive our detection capability is. Rosetta is a pretty reflective object, but it's also quite small when compared to near-Earth objects that could do us any damage. And here we had at least several days' warning of this small object's approach. It's actually comforting to me, in a way; it seems that there is now no way we can have less than a few weeks' warning of the approach of an object large enough to do us some harm. Bad things may happen if such an object hits, but that's enough time to get a lot of people out of harm's way.
Of course, all this hubbub is occasioned by Rosetta's upcoming flyby. The Rosetta Blog has some updates, including the nice detail that no further trajectory correction maneuvers are necessary, which bodes well for them accomplishing the acquisition of science data during the flyby.
Copyright © 1993 - 2007 The Planetary Society. All rights reserved.
--
+++++++++++++++++++++++++++++++++++++++++++
NEO News (now in its thirteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.
NEO News (11/12/07) More on Congress NEO Hearings
This edition of NEO News contains some additional material on the hearings held last week by the House Subcommittee on Space and Aeronautics dealing with advanced NEO searches and related topics. I have (1) posted a news story on the hearing from Physorg.com, (2) selected several very nice summary comments taken from the testimony, and (3) also added a few comments of my own on some misunderstandings that can arise in these discussions, misunderstandings that apparently caused the NASA NEO study to limit itself to technologies for deflecting NEAs between 140m and 1km in diameter, neglecting both the most dangerous (>1km) and the most common (<140m) cases. Also, unrelated to the hearings, there is (4) a post on the strange story off how the Rosetta spacecraft was mistaken for a NEA.
David Morrison
===================================
(1) NASA PRESSED TO AVERT CATASTROPHIC DEEP IMPACT
AFP, 8 November 2007
http://www.physorg.com/news113748841.html
NASA penny-pinching risks exposing humankind to a planetary catastrophe if a big enough asteroid evades detection and slams into Earth, US lawmakers argued Thursday. But the US space agency said the chances of a new "Near-Earth Object" (NEO) like the one that wiped out the dinosaurs were too remote to divert scarce resources.
Scott Pace, head of program analysis and evaluation at NASA, said the agency could not do more to detect NEOs "given the constrained resources and the strategic objectives NASA already has been tasked with."
Pace and other NASA officials were grilled at a congressional hearing on the existing NEO program, which seized the public imagination in the late 1990s through the movies "Armageddon" and "Deep Impact." Lawmakers decried the threatened closure of a giant radio telescope in Puerto Rico run with NASA's assistance that is the world's foremost facility for tracking space objects.
"We're talking about minimal expense compared to the cost of having to absorb this type of damage," Republican Congressman Dana Rohrabacher said. "After all, it may be the entire planet that is destroyed!"
Puerto Rico delegate Luis Fortuno fretted over the economic impact on his impoverished US territory, but also warned of the broader consequences for the entire planet. The National Science Foundation has earmarked the Arecibo Observatory, which featured in science-fiction movie "Contact" and the James Bond installment "Goldeneye," for closure after 2011 if new private-sector money is not found.
NASA officials said they would get by with new monitoring systems, including a network of four telescopes being built in Hawaii by the US Air Force.
Critics say NASA has imposed big cuts on many research programs in a bid to meet President George W. Bush's goal of returning astronauts to the Moon by 2020 and use it as a stepping stone for manned missions to Mars and beyond.
The hearing of the House of Representatives space and aeronautics subcommittee highlighted one small asteroid named Apophis, about 250 meters (273 yards) wide, which some scientists say could swing by Earth on Friday, April 13, 2029. NASA says there is a one in 45,000 chance that Apophis could pass through a "gravitational keyhole" and return to hit the planet in 2036. "It's a very unlikely situation and one we can drive to zero, probably," said Donald Yeomans, who manages the NEO program at NASA's Jet Propulsion Laboratory.
NASA now only tracks NEOs larger than one kilometer (0.62 miles) in diameter, which come near Earth only once every few hundred thousand years. Objects of that size can cause global disaster through their immediate surface impact and by triggering rapid climate change. "Extinction-class" objects measuring at least 10 kilometers, such as the object that crashed into Mexico's Yucatan peninsula about 65 million years ago, would be rarer still.
Lawmakers complained that NASA had failed to come up with a budget in line with a 2005 act of Congress that mandated an expanded search for NEOs that are at least 140 meters in diameter. The agency's annual NEO budget of 4.1 million dollars was attacked as being too meager to cover this goal.
There are about 20,000 smaller objects with the potential to hit home, according to NASA, and Republican Representative Tom Feeney said "they could still inflict large regional impacts if they struck the Earth."
Options to divert space rocks on a collision course with Earth include slamming nuclear missiles into them, although scientists believe that in most cases involving smaller debris, conventional rockets would do the job.
Yeomans said also that while the European and Japanese space agencies are stepping up their own NEO programs, more than 98 percent of the work is now done by NASA.
© 2007 AFP
==================================
(2) BRIEF KEY MESSAGES FROM THE NEO HEARING
From testimony of J. Anthony Tyson, LSST
Until recently, the discussion of risk associated with an impact of a NEO has been statistical; what is the probability? This is similar to considerations of risk in many other areas such as weather and traffic accidents. What if it were feasible to deploy a system that would alert me of an impending traffic accident well in advance? That would change the very nature of that risk from a probabilistic worry to a deterministic actionable situation. The ability to detect virtually every potentially hazardous Near-Earth object and determine its orbit with precision transforms that statistical threat into a deterministic prediction. We face many threats, and virtually all of them are either so complex or unpredictable that they are treated probabilistically even though the social and financial consequences are legion. With a comparatively small investment the NEO risk can be transformed from a probabilistic one to a deterministic one, enabling mitigation.
From testimony of Donald Yeomans, JPL
What should be done in the event of an identified NEO Threat? A number of existing technologies can deflect an Earth threatening asteroid -- if there is time. The primary goal of the PHA survey programs is to discover them early and provide the necessary time. An asteroid that is predicted to hit Earth might require a change in its velocity of only 3 millimeters per second if this impulse were applied twenty years in advance of the impact. The key to a successful deflection is having sufficient time to carry it out, whether it is the slow, gentle drag of a gravity tractor or a more impulsive shove from an impacting spacecraft or explosive device. In either case, a verification process would be required to ensure the deflection maneuver was successful and to ensure the object's subsequent motion would not put it on yet another Earth impacting trajectory. While suitable deflection technologies exist, none of them can be effective if we are taken by surprise. It is the aggressive survey efforts and robust planetary radars that must ensure that the vast majority of potentially hazardous objects are discovered and tracked well in advance of any Earth threatening encounters. The first three steps in any asteroid mitigation process are: Find them early, find them early, and find them early!
From testimony of Russell Schweickart, B612 Foundation
In closing I would suggest a personal perspective based on having spent the last 6 years of my life studying this issue. NEOs are part of nature. A NEO impact is a natural hazard in much the same way as are hurricanes, tsunamis, floods, etc. NEO impacts are deceptively infrequent, yet devastating at potentially unimaginable levels. NEOs are however not our enemies. We do not need to "defend" against NEOs, we need to protect ourselves from their occasional impact, as we do with other natural hazards.
Unlike other natural hazards, however, NEO impacts can be predicted well ahead of time and actually prevented from occurring. If we live up to our responsibility, if we wisely use our amazing technology, and if we are mature enough, as a nation and as a community of nations, there may never again be a substantially damaging asteroid impact on the Earth. We have the ability to make ourselves safe from cosmic extinction. If we cannot manage to meet this challenge, we will, in my opinion, have failed to meet our evolutionary responsibility.
==================================
SOME MISCONSEPTIONS ABOUT NEO IMPACTS
David Morrison
Some of the often misunderstood concepts behind NEO surveys concern the meaning of a specified 90% target size, 1km diameter in the case of the current Spaceguard Survey, and 140m for the proposed Spaceguard deep survey. An example from the news story above is this statement: "NASA now only tracks NEOs larger than one kilometer (0.62 miles) in diameter." But the fact is, in Al Harris's often-quoted words, "we don't throw back the small ones." The majority of NEAs found by Spaceguard are less than 1km in diameter. By the time we reach 90% completeness at 1km, we will have found almost ten times more NEAs smaller than this limit, and certainly these smaller NEAs are tracked and cataloged. The best known example is Apophis, the most dangerous NEA found yet, which is only about half the 1km Spaceguard target size. In any such survey, most of the NEAs will be below the index size, but these will be less complete than the index size used for the 90% metric.
Similarly, any survey scaled for 140m NEAs will predominantly find NEAs smaller than this size. In fact, the discoveries from this deep survey will extend down below the atmospheric cut-off at about 30m diameter. Rusty Schweickart in his testimony estimates that when we reach 90% completeness at 140m, we will be 40% complete for Tunguska-size objects. The most likely object to require deflection is actually below the 140m index size.
There are implications of these facts that need to be considered. For example, the data handling must be scaled for nearly 10 times the number of NEAs at 140m size, since again, we won't throw back the small ones. Further, any plans for deflection should recognize that the most likely challenges will come from NEAs less than 140m in diameter. The NASA study apparently focused only on deflecting NEAs between 140m and 1km in diameter, neglecting both the most dangerous (those larger than 1km, of which 10% will remain undiscovered at the nominal end of the current Spaceguard survey) and the most common (those under 140m diameter).
None of the prepared testimony explicitly mentioned uncertainties in the population of small NEAs or in the ability to model the efficiency of survey telescopes. This in understandable, given the limited time available, but it does over-emphasize specific dates and sizes that enter into models of the new deep surveys. It is not unreasonable that both the number of NEAs larger than 140m and the ability of new telescopes (both ground-based and space based) to detect and identify them could be off by as much as a factor of two. We won't know when we are likely to achieve 90% completeness at 140m until the telescopes are built and the new survey is well underway. Therefore I don't worry too much about small differences in the estimated dates of completion. I am more interested in the start date than the completion date for Spaceguard-2.
=================================
(4) THAT'S NO NEAR-EARTH OBJECT, IT'S A SPACESHIP
The Planetary Society Weblog, 9 November 2007
http://www.planetary.org/blog/article/00001227/
By Emily Lakdawalla
Whenever I am out at night with my husband and I point to the sky and say, "that's Venus" or "look, that's Saturn, see how yellow it is," he likes to burst my bubble by saying "no, it's just a plane." Every great once in a while, I'm sad to say, he's right.
Well, a similar scenario has just unfolded within the near-Earth asteroid community. On November 8 the Minor Planet Center issued a routine Minor Planet Electronic Circular, reporting on observations of a newly discovered object, newly designated 2007 VN84. Several observatories had spotted the faint object, and, based upon those observations, an orbital trajectory was calculated, which placed the object on a very close path by Earth, "0.000081 AU (1.89 Earth radii) on Nov 13.844 UT." Now, that 1.89 Earth radii is measured relative to Earth's center, meaning that the thing was going to fly within 6,000 kilometers of Earth on November 13 at 20:15 UTC. That's pretty close! This is a truly near-Earth object.
Rosetta's second Earth flyby is due to take place Closest approach will take place on 13 November 2007 at 20:57 UTC, at which time Rosetta will speed past at 45,000 km/h (about 12.5 km/s) relative to Earth. At this time, Rosetta will be 5,301 km above the Pacific Ocean, south-west of Chile, at 63° 46' south and 74° 35' west. But a sharp-eyed reader of the MPECs, Denis Denisenko, realized that there was something going on. I'm not sure what tipped him off; whether he noticed that specific date and time and remembered another significant event to happen on that day, or whether he has a habit of checking near-Earth object trajectories against catalogs of manmade objects. However the discovery happened, he realized that 2007 VN84 had a trajectory that was awfully similar to Rosetta, which is due to swing by Earth on November 13 at 20:57 UTC. He posted as much to the Minor Planet Mailing List.
Indeed, today, the Minor Planet Center issued an Editorial Notice stating that further investigation has shown that the object briefly designated 2007 VN84 is, in fact, the Rosetta spacecraft, and that the designation "2007 VN84" will be retired. The editorial notice goes on to say, with notable asperity, "This incident, along with previous NEOCP postings of the WMAP spacecraft, highlights the deplorable state of availability of positional information on distant artificial objects.... A single source for information on all distant artificial objects would be very desirable."
I think it's pretty funny that a very big spacecraft designed to study minor planets in the solar system has itself, however briefly, been named among the minor planets. This episode also goes to show how sensitive our detection capability is. Rosetta is a pretty reflective object, but it's also quite small when compared to near-Earth objects that could do us any damage. And here we had at least several days' warning of this small object's approach. It's actually comforting to me, in a way; it seems that there is now no way we can have less than a few weeks' warning of the approach of an object large enough to do us some harm. Bad things may happen if such an object hits, but that's enough time to get a lot of people out of harm's way.
Of course, all this hubbub is occasioned by Rosetta's upcoming flyby. The Rosetta Blog has some updates, including the nice detail that no further trajectory correction maneuvers are necessary, which bodes well for them accomplishing the acquisition of science data during the flyby.
Copyright © 1993 - 2007 The Planetary Society. All rights reserved.
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NEO News (now in its thirteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.
08 November 2007
U.S. House Comm. Hearing on 08 November 2007: Near-Earth Objects (NEOs)—Status of the Survey Program and Review of NASA’s 2007 Report to Congress
U.S. HOUSE OF REPRESENTATIVES
COMMITTEE ON SCIENCE AND TECHNOLOGY
SUBCOMMITTEE ON SPACE AND AERONAUTICS
Near-Earth Objects (NEOs)—Status of the Survey Program and Review of NASA’s 2007 Report to Congress
Thursday, November 8, 2007
10:00 a.m. – 12:00 p.m.
2318 Rayburn House Office Building
Washington, D.C. USA
Purpose: On Thursday, November 8, 2007 at 10:00 a.m., the House Committee on Science and Technology’s Subcommittee on Space and Aeronautics will hold a hearing to examine the status of NASA’s Near-Earth Object survey program, review the findings and recommendations of NASA’s report to Congress, Near-Earth Object Survey and Deflection Analysis of Alternatives, and to assess NASA’s plans for complying with the requirements of Section 321 of the NASA Authorization Act of 2005.
Witnesses
Panel 1
- The Honorable Luis G. Fortuño, Resident Commissioner, Puerto Rico
Panel 2
- Dr. James Green, Science Mission Directorate, NASA
- Dr. Scott Pace, Program Analysis and Evaluation, NASA
- Dr. Donald K.Yeomans, Jet Propulsion Laboratory
- Dr. Donald B.Campbell, Cornell University
- Mr. Russell Schweickart, B612 Foundation
- Dr. J. Anthony Tyson, University of California, Davis
Link: Article - 08 November 2007 (NASA pressed to avert catastrophic Deep Impact)
Link: U.S. House Science Comm. Hearing Information
Link: Hearing Charter (PDF)
Link: Testimony of Chairman Mark Udall, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress
Link: Testimony of Rep. Luis G. Fortuno, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress
Link: Testimony of James Green, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress
Link: Testimony of Scott Pace, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress
Link: Testimony of Donald Yeomans, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress
Link: Testimony of Russell Schweickart, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress
Link: Testimony of J. Anthony Tyson, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress
Journal Article: "A possible impact crater for the 1908 Tunguska Event"
Summary from Slashdot.org:
"A team of scientists from the Marine Science Institute in Bologna [Italy] claims to have found the crater left by the aerial blast of a comet or asteroid in 1908 in the Tunguska region of Siberia. The blast flattened 770 square miles (2,000 square kilometers) of forest, but to date no remains or crater have been found. This has left open the question of what kind of object made the impact. The team believes that, contrary to previous studies, nearby Lake Cheko is only one century old and 'If the body was an asteroid, a surviving fragment may be buried beneath the lake. If it was a comet, its chemical signature should be found in the deepest layers of sediments.' The team's findings are based on a 1999 expedition to Tunguska and appeared in the August issue of the journal Terra Nova."
Journal Reference:
Terra Nova, 00, 1–7
Volume 19 Issue 4 Page 245-251, August 2007
"A possible impact crater for the 1908 Tunguska Event"
Luca Gasperini, Geologia Marina, Istituto di Scienze Marine, CNR, Via Gobetti 101, Bologna 40129, Italy. Tel.: +39 051 639 8901; fax: +39 051 639 8901; e-mail: luca.gasperini@ismar.cnr.it
Abstract:
The so-called ‘Tunguska Event’ refers to a major explosion that occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2000 km2 of taiga, globally detected pressure and seismic waves, and bright luminescence in the night skies of Europe and Central Asia, combined with other unusual phenomena. The ‘Tunguska Event’ may be related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report results from the investigation of Lake Cheko, located ~8 km NNW of the inferred explosion epicenter. Its funnel-like bottom morphology and the structure of its sedimentary deposits, revealed by acoustic imagery and direct sampling, all suggest that the lake fills an impact crater. Lake Cheko may have formed due to a secondary impact onto alluvial swampy ground; the size and shape of the crater may have been affected by the nature of the ground and by impact-related melting and degassing of a permafrost layer.
Link: National Geographic Article
Link: Terra Nova Journal (August 2007)
Link: Terra Nova Journal Article
Link: Terra Nova Journal Article PDF
"A team of scientists from the Marine Science Institute in Bologna [Italy] claims to have found the crater left by the aerial blast of a comet or asteroid in 1908 in the Tunguska region of Siberia. The blast flattened 770 square miles (2,000 square kilometers) of forest, but to date no remains or crater have been found. This has left open the question of what kind of object made the impact. The team believes that, contrary to previous studies, nearby Lake Cheko is only one century old and 'If the body was an asteroid, a surviving fragment may be buried beneath the lake. If it was a comet, its chemical signature should be found in the deepest layers of sediments.' The team's findings are based on a 1999 expedition to Tunguska and appeared in the August issue of the journal Terra Nova."
Journal Reference:
Terra Nova, 00, 1–7
Volume 19 Issue 4 Page 245-251, August 2007
"A possible impact crater for the 1908 Tunguska Event"
Luca Gasperini, Geologia Marina, Istituto di Scienze Marine, CNR, Via Gobetti 101, Bologna 40129, Italy. Tel.: +39 051 639 8901; fax: +39 051 639 8901; e-mail: luca.gasperini@ismar.cnr.it
Abstract:
The so-called ‘Tunguska Event’ refers to a major explosion that occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2000 km2 of taiga, globally detected pressure and seismic waves, and bright luminescence in the night skies of Europe and Central Asia, combined with other unusual phenomena. The ‘Tunguska Event’ may be related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report results from the investigation of Lake Cheko, located ~8 km NNW of the inferred explosion epicenter. Its funnel-like bottom morphology and the structure of its sedimentary deposits, revealed by acoustic imagery and direct sampling, all suggest that the lake fills an impact crater. Lake Cheko may have formed due to a secondary impact onto alluvial swampy ground; the size and shape of the crater may have been affected by the nature of the ground and by impact-related melting and degassing of a permafrost layer.
Link: National Geographic Article
Link: Terra Nova Journal (August 2007)
Link: Terra Nova Journal Article
Link: Terra Nova Journal Article PDF
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