From Dave Morrison.
NEO News (07/30/09) Impact on Jupiter
The big news this week is the apparent impact on Jupiter that took place on July 19, 2009. This appears analogous to the 1996 impacts of Comet Shoemaker-Levy 9, except that in this case the hit was from a single projectile, probably no more than 1 km across. It has been generally called a comet in the press, although no one knows what it was made of or its orbit before hitting Jupiter. This new impact scar on Jupiter has stimulated considerable press interest in the impact threat, including some suggestions that we need to devote more resources to protecting the Earth.
The NASA NEO Program Office at JPL has inaugurated a new program to provide timely information on NEOs via Twitter and Widget. The discovery and orbit calculations for all NEOs have been available for several years at (neo.jpl.nasa.gov), but now they are adding a more user-friendly format for the general public (jpl.nasa.gov/asteroidwatch).
Coincidentally, there is also news that the U.S. Air Force will re-instate its release of information on space observations of bright fireballs, although there are no details indicating just what information will be provided or how quickly the data release will take place. This edition of NEO News is made up of various news releases and press commentary on these recent events.
David Morrison
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NATURE NEWS: FIREBALL DATA WILL BE AVAILABLE AGAIN
Published online 8 July 2009 | Nature 460, 163 (2009) News in Brief
US Air Force will continue to share meteor data
The United States Air Force says that it will resume sharing data on incoming meteors with astronomers. The Air Force collects the data with a network of satellites and sensors designed as a missile early warning system. For more than a decade, it provided them to astronomers on an ad-hoc basis, but the informal relationship came to a halt earlier this year (see Nature 459, 896-897; 2009). Astronomers feared that the Air Force had put a stop to the practice, but "the data will still flow", says Andy Roake, a spokesman for Air Force Space Command in Colorado Springs, Colorado. The Air Force is developing procedures for releasing data that will be faster, more systematic and in compliance with classification procedures. Data sharing could resume within the next few months.
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NEW NASA IMAGES INDICATE OBJECT HITS JUPITER
Jet Propulsion Laboratory, Pasadena, Calif. July 20, 2009
Scientists have found evidence that another object has bombarded Jupiter, exactly 15 years after the first impacts by the comet Shoemaker-Levy 9. Following up on a tip by an amateur astronomer that a new dark "scar" had suddenly appeared on Jupiter, this morning between 3 and 9 a.m. PDT (6 a.m. and noon EDT) scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., using NASA's Infrared Telescope Facility at the summit of Mauna Kea, Hawaii, gathered evidence indicating an impact.
New infrared images show the likely impact point was near the south polar region, with a visibly dark "scar" and bright upwelling particles in the upper atmosphere detected in near-infrared wavelengths, and a warming of the upper troposphere with possible extra emission from ammonia gas detected at mid-infrared wavelengths
"We were extremely lucky to be seeing Jupiter at exactly the right time, the right hour, the right side of Jupiter to witness the event. We couldn't have planned it better," said Glenn Orton, a scientist at JPL.
The new Jupiter images are online at: http://www.jpl.nasa.gov/news/news.cfm?release=2009-112 .
Orton and his team of astronomers kicked into gear early in the morning and haven't stopped tracking the planet. They are downloading data now and are working to get additional observing time on this and other telescopes.
This image was taken at 1.65 microns, a wavelength sensitive to sunlight reflected from high in Jupiter's atmosphere, and it shows both the bright center of the scar (bottom left) and the debris to its northwest (upper left). "It could be the impact of a comet, but we don't know for sure yet," said Orton. "It's been a whirlwind of a day, and this on the anniversary of the Shoemaker-Levy 9 and Apollo anniversaries is amazing." Shoemaker-Levy 9 was a comet that had been seen to break into many pieces before the pieces hit Jupiter in 1994.
Leigh Fletcher, a NASA postdoctoral student at JPL who worked with Orton during these latest observations said, "Given the rarity of these events, it's extremely exciting to be involved in these observations. These are the most exciting observations I've seen in my five years of observing the outer planets!"
The observations were made possible in large measure by the extraordinary efforts of the Infrared Telescope Facility staff, including telescope operator William Golisch, who adroitly moved three instruments in and out of the field during the short time the scar was visible on the planet, providing the wide wavelength coverage.
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JUPITER'S BEEN HIT!
By Richard A. Kerr, Science NOW Daily News, 20 July 2009
A large object has slammed into Jupiter, leaving behind a giant black smudge that was first reported yesterday by an amateur astronomer. The find is only the second time in recorded history that scientists have glimpsed an impact scar in the atmosphere of a giant planet. "I never expected I'd get to see something like this," says astronomer Leigh Fletcher, a postdoc at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.
Amateur astronomer Anthony Wesley had been taking routine images of Jupiter through his 37-centimeter telescope (pros would be on a 1000-centimeter instrument) in Murrumbateman, Australia, at about 11:30 p.m. local time, when he noticed something unusual: a dark spot several thousands of kilometers across rotating into view high in Jupiter's south polar region (see picture). Wesley had been about to end his observing run, and he initially considered passing the spot off as a typical dark polar storm. But he decided to keep at it, and in 15 minutes more he believed he was seeing something else entirely.
Wesley suspected an impact and soon contacted Fletcher and JPL astronomer Glenn Orton. As luck would have it, the duo had previously scheduled time on the NASA Infrared Telescope on Hawaii (remotely operated from JPL), so they took a closer look. They found the same distinctive infrared signature as Orton and others saw 15 years ago this week when the 21-plus fragments of disrupted comet Shoemaker-Levy 9 slammed into Jupiter one after the other (Science, 29 July 1994, p. 601). "We've been incredibly fortunate to have a talented amateur report this within hours," says Fletcher. Such amateurs "are doing some of the fundamental work of observing what's happening on Jupiter," adds Orton.
The impact "was a bit of a surprise," says astronomer Heidi Hammel of the Space Science Institute in Boulder, Colorado, who observed the 1994 impacts with the Hubble Space Telescope. "We all thought these were a little more rare." This one--a solitary event so far--looks like one of Shoemaker-Levy 9's medium-size impacts, says Hammel. How large the rocky asteroid or icy comet was is hard to estimate, says astronomer Harold Weaver of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. There was never any consensus on the size of the Shoemaker-Levy 9 objects, but this one might have been several hundred meters across--a kilometer at most--and traveling at tens of thousands of kilometers per hour.
If scientists are to retrieve any new information about jovian impacts, they'll have to be quick about it. Winds are tearing the black splotch apart even as astronomers race to submit their emergency proposals for telescope time--including time on the recently renovated Hubble Space Telescope.
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JUPITER GETS A BLACK EYE
The Wall Street Journal, July 24, 2009, By Michio Kaku
We sometimes forget that the universe is a violent place. This week, astronomers in Hawaii recorded an exceedingly rare event. An amazing photograph revealed a comet or asteroid, probably no more than a mile across, plowing into Jupiter's atmosphere. The impact created a fireball roughly the size of the planet earth.
The good news is that Jupiter was just doing its job, cleaning out the solar system of stray comets and asteroids. Jupiter, 318 times more massive than the earth, acts like a cosmic vacuum cleaner, sucking in or deflecting debris left over from the solar system's birth 4.5 billion years ago. If it weren't for Jupiter's colossal gravitational field, we wouldn't be here, since the Earth would be hit with deadly comet and meteor impacts every month or so. Most of the U.S. would just be an empty graveyard of bleak craters.
The bad news is that a comet impact could happen to us. A black eye for Jupiter would be a body blow to the earth. We got a taste of this back in 1908, when something the size of an apartment building plowed into Tunguska, Siberia. This "city-buster" flattened 100 million trees with the force of a hydrogen bomb. But this recent Jupiter comet, much larger and coming in at perhaps 100,000 miles per hour, would have unleashed the power of hundreds of H-bombs. It might have engulfed most of the East Coast in a huge firestorm, triggering a massive tsunami and destabilizing the weather.
According to Hollywood, we can always send our astronauts on a space shuttle to intercept a comet and blow it up with H-bombs. Wrong. Blowing up a comet with nuclear bombs creates chunks of debris, increasing the area of destruction. So we are sitting ducks to a potential impact from deep space.
So what's the lesson from all of this? Maybe Mother Nature has a sense of humor. An impact like the recent one in Jupiter happened 15 years ago, in late July, after the Shoemaker-Levy 9 comet broke up into 20 pieces, each of which plunged into Jupiter, creating a dazzling display of cosmic fireworks. Scientists used to believe that these collisions took place once every few thousand years, not 15 years. So perhaps Mother Nature was just trying to show what little scientists really understand about these cosmic collisions.
But it also happened on the 40th anniversary of the Moon landing. So maybe Mother Nature was reminding us that the universe is, after all, a violent place-that we may one day need a new home. The Earth lies in the middle of a cosmic shooting gallery. The proof comes out every night when we gaze at the Moon. When viewing the film of Neil Armstrong and Buzz Aldrin bobbing among the barren craters of the Moon, we are reminded that each crater was gouged out by a titanic impact.
In addition, there are more than 5,000 so-called near-Earth objects, carefully tracked by telescope, that can cross near the orbit of the earth. One of them, the asteroid Apophis, is about the size of the Rose Bowl. It will graze the Earth in 2029 and again in 2036, passing below some of our satellites.
But there are also many unnamed comets outside the solar system whose orbits are totally unknown and unpredictable. They would give us little warning and catch us totally off-guard, like the comet that just hit Jupiter.
So in the long term, perhaps we should look at the space program as an insurance policy. Not only has the space program given us a bonanza of benefits (such as weather satellites, the Global Positioning System, telecommunications, etc.), it also provides a gateway to the stars. Over the course of the next few centuries, maybe we should use that gateway to plan to be a "two planet species." Life is too precious to place in one basket.
In August, President Barack Obama will receive a major report from the U.S. human space flight plans committee about the future of space travel, which could be a turning point for NASA in the 21st century. He should remember the Jupiter hit as he considers the report.
-Mr. Kaku is the author of "Physics of the Impossible: a Scientific Exploration into the World of Phasers, Force Fields, Teleportation, and Time Travel" (Doubleday, 2008).
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JUPITER: OUR COSMIC PROTECTOR?
By Dennis Overbye, New York Times, July 25, 2009
Jupiter took a bullet for us last weekend. An object, probably a comet that nobody saw coming, plowed into the giant planet's colorful cloud tops sometime Sunday, splashing up debris and leaving a black eye the size of the Pacific Ocean. This was the second time in 15 years that this had happened. The whole world was watching when Comet Shoemaker-Levy 9 fell apart and its pieces crashed into Jupiter in 1994, leaving Earth-size marks that persisted up to a year.
That's Jupiter doing its cosmic job, astronomers like to say. Better it than us. Part of what makes the Earth such a nice place to live, the story goes, is that Jupiter's overbearing gravity acts as a gravitational shield deflecting incoming space junk, mainly comets, away from the inner solar system where it could do for us what an asteroid apparently did for the dinosaurs 65 million years ago. Indeed, astronomers look for similar configurations - a giant outer planet with room for smaller planets in closer to the home stars - in other planetary systems as an indication of their hospitableness to life.
Anthony Wesley, the Australian amateur astronomer who first noticed the mark on Jupiter and sounded the alarm on Sunday, paid homage to that notion when he told The Sydney Morning Herald, "If anything like that had hit the Earth it would have been curtains for us, so we can feel very happy that Jupiter is doing its vacuum-cleaner job and hoovering up all these large pieces before they come for us."
But is this warm and fuzzy image of the King of Planets as father-protector really true? "I really question this idea," said Brian G. Marsden of the Harvard-Smithsonian Center for Astrophysics, referring to Jupiter as our guardian planet. As the former director of the International Astronomical Union's Central Bureau for Astronomical Telegrams, he has spent his career keeping track of wayward objects, particularly comets, in the solar system. Jupiter is just as much a menace as a savior, he said. The big planet throws a lot of comets out of the solar system, but it also throws them in.
Take, for example, Comet Lexell, named after the Swedish astronomer Anders Lexell. In 1770 it whizzed only a million miles from the Earth, missing us by a cosmic whisker, Dr. Marsden said. That comet had come streaking in from the outer solar system three years earlier and passed close to Jupiter, which diverted it into a new orbit and straight toward Earth. The comet made two passes around the Sun and in 1779 again passed very close to Jupiter, which then threw it back out of the solar system.
"It was as if Jupiter aimed at us and missed," said Dr. Marsden, who complained that the comet would never have come anywhere near the Earth if Jupiter hadn't thrown it at us in the first place.
Hal Levison, an astronomer at the Southwest Research Institute, in Boulder, Colo., who studies the evolution of the solar system, said that whether Jupiter was menace or protector depended on where the comets came from. Lexell, like Shoemaker Levy 9 and probably the truck that just hit Jupiter, most likely came from an icy zone of debris known as the Kuiper Belt, which lies just outside the orbit of Neptune, he explained. Jupiter probably does increase our exposure to those comets, he said.
But Jupiter helps protect us, he said, from an even more dangerous band of comets coming from the so-called Oort Cloud, a vast spherical deep-freeze surrounding the solar system as far as a light-year from the Sun. Every once in a while, in response to gravitational nudges from a passing star or gas cloud, a comet is unleashed from storage and comes crashing inward.
Jupiter's benign influence here comes in two forms. The cloud was initially populated in the early days of the solar system by the gravity of Uranus and Neptune sweeping up debris and flinging it outward, but Jupiter and Saturn are so strong, Dr. Levison said, that, first of all, they threw a lot of the junk out of the solar system altogether, lessening the size of this cosmic arsenal. Second, Jupiter deflects some of the comets that get dislodged and fall back in, Dr. Levison said. "It's a double anti-whammy," he said.
Asteroids pose the greatest danger of all to Earth, however, astronomers say, and here Jupiter's influence is hardly assuring. Mostly asteroids live peacefully in the asteroid belt between Mars and Jupiter, whose gravity, so the standard story goes, keeps them too stirred to coalesce into a planet but can cause them to collide and rebound in the direction of Earth.
That's what happened, Greg Laughlin of the University of California at Santa Cruz, said, to a chunk of iron and nickel about 50 yards across roughly 10 million to 100 million years ago. The result is a hole in the desert almost a mile wide and 500 feet deep in northern Arizona, called Barringer Crater. A gift, perhaps, from our friend and lord, Jupiter. [Note from DM: The accepted age of Meteor [Barringer] Crater is 50,000 years, orders of magnitude less than 10-100 million years.]
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COULD EARTH BE HIT, LIKE JUPITER JUST WAS?
Charles Q. Choi, space.com - Jul 28, 2009
The recent bruising Jupiter received from a cosmic impact is a violent reminder that our solar system is a shooting gallery that sometimes blasts Earth. Still, what are the odds of a cosmic impact threatening our planet?
So far 784 near-Earth objects (NEOs) more than a half-mile wide (1 km) have been found. "If an object of about the same size that just hit Jupiter also hit Earth - it was probably a typical cometary object of a kilometer or so in size (0.6 miles) - it would have been fairly catastrophic," explained astronomer Donald Yeomans, manager of NASA's Near-Earth Object program office at the Jet Propulsion Laboratory in Pasadena, Calif.
Scientists have ruled out the chances of an Earth impact for all of these 784 large NEOs. Still, lesser objects also pose a risk, and researchers estimate more than 100 large NEOs remain to be found.
Billions of years ago, impacts were far more common. Our Moon retains a record of the pummeling it and Earth took: the Moon's craters remain, while on Earth, most scars of ancient impacts have been folded back into the planet or weathered away.
Today's solar system is far less crowded, and in fact Jupiter, having more mass and gravity, scoops up a lot of the dangerous objects, as does the sun. Currently just one NEO of all the objects scientists are tracking poses any significant chance of hitting the Earth - 2007 VK184. If this roughly 425-foot-wide (130 meters) asteroid hit our planet, it would strike with an energy of roughly 150 million tons of TNT, or more than 10,000 times that of the atom bomb dropped on Hiroshima.
Roughly 100 telescopic observations made so far suggest that 2007 VK184 has a 1-in-2,940 chance of hitting Earth 40 to 50 years from now. However, if the past is any guide, further observations to refine computations of its orbit very likely will downgrade its probability of hitting Earth to virtually nothing, Yeomans said.
Of remaining concern are the NEOs that we do not see. Researchers suspect about 156 large NEOs 1 kilometer in diameter or larger remain to be found, and when it comes to dangerous NEOs in general, "when we get down to 140 meters (460 feet) or larger diameter objects, we think we've discovered about 15 percent of them, and with 50 meters (164 feet) or larger diameter, we've discovered less than 5 percent of them," Yeomans explained.
On average, an NEO roughly a half-mile wide or larger hits the Earth roughly every 500,000 years, "so we're not expecting one anytime soon," Yeomans explained. "For 500 meters (1,640 feet), we're talking a mean interval of about 100,000 years," he added. "When you get down to 50 meters, the mean interval is about 700 years, and for 30 meters (98 feet), about 140 years or so, but by then you're getting down to a size where you won't expect any ground damage, as they burn up in the atmosphere at about 25 meters (82 feet) in diameter and smaller, probably for an impressive fireball event."
When it comes to truly monstrous NEOs some 10 kilometers (6.2 miles) or larger, of the size thought to have helped kill off the dinosaurs, "that's a 100 million year event, and in fact, I don't think there is anything like that we see right now," Yeomans said. "The largest near-Earth object that can actually cross the Earth's path, Sisyphus, has a diameter of 8 kilometers (5 miles), and the largest that is termed a potential hazard is Toutatis, which has a diameter of approximately 5.4 km (3.35 miles)."
Keeping watch; There are currently four teams worldwide actively looking for both large and small NEOs, Yeomans said. "We're concentrating on the large ones for now, but hopefully with the next generation of search, we'll be more efficient in finding the smaller objects, to find 90 percent of the total population of potential hazards larger than 140 meters," he added.
Keeping an eye on NEOs might not just be healthy for humanity, but also help lead us out into space. "They're easy objectives to get to, and asteroids have significant metal resources that can be mined, while comets have significant water resources for space habitats or travel," Yeomans said. "If you want to build a habitat in space, you're not going to build it all on the ground and launch it up, since that's too expensive - you want to go up and look for resources instead."
Furthermore, asteroids and comets are among the objects that have changed the least since the birth of the solar system roughly 4.6 billion years ago, and might reveal vital clues behind the mysterious process. "They may well have delivered the water and carbon-based molecules to Earth that allowed life to form, so they're extremely important for study in that direction," Yeomans added.
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WEB UPDATES ON NEOS FROM NASA
Jet Propulsion Laboratory, Pasadena, Calif.
Internet Advisory: 2009-115. July 29, 2009
NASA to Provide Web Updates on Objects Approaching Earth
PASADENA, Calif. -- NASA's Jet Propulsion Laboratory is introducing a new Web site that will provide a centralized resource for information on near-Earth objects - those asteroids and comets that can approach Earth. The "Asteroid Watch" site also contains links for the interested public to sign up for NASA's new asteroid widget and Twitter account.
"Most people have a fascination with near-Earth objects," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at JPL. "And I have to agree with them. I have studied them for over three decades and I find them to be scientifically fascinating, and a few are potentially hazardous to Earth. The goal of our Web site is to provide the public with the most up-to-date and accurate information on these intriguing objects."
The new Asteroid Watch site is online at http://www.jpl.nasa.gov/asteroidwatch. It provides information on NASA's missions to study comets, asteroids and near-Earth objects, and also provides the basic facts and the very latest in science and research on these objects. News about near-Earth object discoveries and Earth flybys will be available and made accessible on the site via a downloadable widget and RSS feed. And for those who want to learn about their space rocks on the go, a Twitter feed is o ffered. "Asteroid Watch" also contains a link to JPL's more technical Near-Earth Objects Web site, where many scientists and researchers studying near-Earth objects go for information.
"This innovative new Web application gives the public an unprecedented look at what's going on in near-Earth space," said Lindley Johnson, program executive for the Near-Earth Objects Observation program at NASA Headquarters in Washington. NASA supports surveys that detect and track asteroids and comets passing close to Earth. The Near-Earth Object Observation Program, commonly called "Spaceguard," also plots the orbits of these objects to determine if any could be potentially hazardous to our planet.
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PLANETARY SOCIETY POLL OF MEMBERS
July 29, 2009
The results of our 2009 Member Survey tell us loud and clear that the number-one supported Planetary Society program-with nearly 90 percent of Society members strongly behind it-is "Monitoring potentially dangerous near-Earth asteroids and comets."
We couldn't agree more. An asteroid or comet impact may be a rare event, but when one happens, all life on Earth could be affected. Just ask the dinosaurs...
So we're asking you to help support the Society's three-part initiative to address this important threat:
1. Gene Shoemaker NEO Grants: This program offers small, but crucial, financial awards to amateur and under-funded professional observers who are making substantial contributions to vital near-Earth object research.
2. Apophis Mission Design Competition: Last year's successful competition designed ways to tag and track this asteroid. The next step might be to design a mission to send human investigators to explore and characterize a threatening object, such as Apophis.
3. Advocacy Action: As the largest grassroots space organization, we must mobilize public support and leverage our partnerships in the astronomical community to force action now.
Protecting our planet from a catastrophic hit is not a problem that can wait until tomorrow. It's not an exaggeration to say that an incoming asteroid or comet could devastate our civilization. It's the only preventable natural disaster and we need to act now to prepare our defenses.
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NEO News (now in its fifteenth 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.
01 August 2009
25 June 2009
Shuttle Plumes Aid in Confirming Comet Explosion at Tunguska in 1908
Noctilucent clouds observed from Donnelley Dome near Fairbanks, Alaska, resulting from a post-space shuttle plume in August 2007 (Credit: M.J. Taylor and C.D. Burton/Utah State University). Kelley, M. C., C. E. Seyler, and M. F. Larsen (2009), Two-dimensional turbulence, space shuttle plume transport in the thermosphere, and a possible relation to the Great Siberian Impact Event, Geophys. Res. Lett., doi:10.1029/2009GL038362, in press (accepted 22 June 2009).
From the article in Universe Today:
The 1908 Tunguska event has always been mysterious and intriguing because no one has been able to fully explain the explosion that leveled 830 square miles of Siberian forest. But the latest research has concluded that the Tunguska explosion was almost certainly caused by a comet entering the Earth’s atmosphere. And how researcher Michael Kelly from Cornell University came to that conclusion it quite interesting: He analyzed the space shuttle's exhaust plume and noctilucent clouds.
“It’s almost like putting together a 100-year-old murder mystery,” said Kelley, a professor of Engineering, who led the research team. “The evidence is pretty strong that the Earth was hit by a comet in 1908.” Previous speculation had ranged from comets to meteors.
Noctilucent clouds are brilliant, night-visible clouds made of ice particles and only form at very high altitudes and in extremely cold temperatures. These clouds appeared a day after the Tunguska explosion and also appear following a shuttle mission.
The researchers contend that the massive amount of water vapor spewed into the atmosphere by the 1908 comet’s icy nucleus was caught up in swirling eddies with tremendous energy by a process called two-dimensional turbulence, which explains why the noctilucent clouds formed a day later many thousands of miles away.
Noctilucent clouds over Saimaa. Credit: Wikipedia
Noctilucent clouds are the Earth’s highest clouds, forming naturally in the mesosphere at about 55 miles over the polar regions during the summer months when the mesosphere is around minus 180 degrees Fahrenheit (minus 117 degrees Celsius).
The space shuttle exhaust plume, the researchers say, resembled the comet’s action. A single space shuttle flight injects 300 metric tons of water vapor into the Earth’s thermosphere, and the water particles have been found to travel to the Arctic and Antarctic regions, where they form the clouds after settling into the mesosphere.
Kelley and collaborators saw the noctilucent cloud phenomenon days after the space shuttle Endeavour (STS-118) launched on Aug. 8, 2007. Similar cloud formations had been observed following launches in 1997 and 2003.
Following the Tunguska Event, the night skies shone brightly for several days across Europe, particularly Great Britain — more than 3,000 miles away. Kelley said he became intrigued by the historical eyewitness accounts of the aftermath, and concluded that the bright skies must have been the result of noctilucent clouds. The comet would have started to break up at about the same altitude as the release of the exhaust plume from the space shuttle following launch. In both cases, water vapor was injected into the atmosphere.
The scientists have attempted to answer how this water vapor traveled so far without scattering and diffusing, as conventional physics would predict.
“There is a mean transport of this material for tens of thousands of kilometers in a very short time, and there is no model that predicts that,” Kelley said. “It’s totally new and unexpected physics.”
This “new” physics, the researchers contend, is tied up in counter-rotating eddies with extreme energy. Once the water vapor got caught up in these eddies, the water traveled very quickly — close to 300 feet per second.
Scientists have long tried to study the wind structure in these upper regions of the atmosphere, which is difficult to do by such traditional means as sounding rockets, balloon launches and satellites, explained Charlie Seyler, Cornell professor of electrical engineering and paper co-author.
“Our observations show that current understanding of the mesosphere-lower thermosphere region is quite poor,” Seyler said. The thermosphere is the layer of the atmosphere above the mesosphere.
"1908 Tunguska Event Caused by Comet, New Research Reveals"
24 June 2009
Nancy Atkinson
Universe Today
Link: Article from Universe Today
"Tunguska impact riddle solved at last"
24 June 2009
SkyMania News
Link: Article from SkyMania
Link: Paper: Two-dimensional turbulence, space shuttle plume transport in the thermosphere, and a possible relation to the Great Siberian Impact Event
Link: Cornell University News Release
23 June 2009
New Fact Sheet from the Secure World Foundation on NEOs
There is a new fact sheet from the Secure World Foundation (SWF) on NEOs. Perhaps a good primer for those interested.
Link: Fact Sheet from SWF (PDF)
Link: News Announcement from SWF on NEOs
Link: Fact Sheet from SWF (PDF)
Link: News Announcement from SWF on NEOs
New Spaceguard Telescope in the UK
UK Spaceguard CentreFrom the article...
A telescope worth £500,000 which will monitor the threat posed by asteroids to earth is being delivered to an observatory in Powys.
The Spaceguard Centre, in Knighton, has been given the Schmidt camera free of charge by the Institute of Astronomy at Cambridge University.
It will be used to spot near earth objects and then track them.
The telescope is not used in Cambridge anymore because of light pollution, but Powys' dark skies are said to be ideal.
The telescope is expected to arrive in Knighton later on Friday, but it could be months before it is installed.
It will be stored temporarily at a water bottling plant in the town.
The Spaceguard Centre started a campaign to raise £54,000 to install the Schmidt camera in January 2008.
The large telescope has a wide field of view and takes photographs of the sky.
A spokeswoman for the Spaceguard centre said the Schmidt camera was 40 years old and was worth about £500,000.
She described it as a "phenomenal piece of British engineering".
It is thought the telescope will work well in Knighton because the sky above the town is free, in the main, from light pollution.
Jay Tate, who runs the centre, has said previously: "Nasa searches for near earth objects and it funds six telescopes in the US and two in Italy and Australia, but no-one else is doing this sort of work in the UK.
"(The telescope) would mean we could search for objects as well as tracking them once they have been identified."
The Spaceguard Centre currently has a robotic telescope, which is able to track asteroids and its observatory attracts school parties and tourists.
Link: BBC Article
18 June 2009
NEO News (06/18/09) Summer Stories
From Dave Morrison.
NEO News (06/18/09) Summer Stories
This edition of NEO news is devoted to several current stories that are creating some press and public interest. Some are serious, others are just summer madness. In any case, it is perhaps useful that we be aware of these issues.
David Morrison
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SURVEILLANCE SATELLITE DATA ON BRIGHT FIREBALLS
As first discussed a week ago in an article by Leonard David on Space.com, there is a move to stop releasing the routine observations of large fireballs that have been made by U.S. surveillance satellites. Peter Brown at University of Western Ontario and others have made good use of these data to define the impact frequency for objects in the meter size range and to help locate meteorite falls such as Tagish Lake. This is a serious issue, although some news sources are greatly exaggerating by claiming that the absence of global fireball data somehow increases public risk from impacts. Unfortunately, this topic feeds those who are already paranoid about government secrecy. Following is a sober summary of the issues from Nature on-line:
ASTRONOMERS LOSE ACCESS TO MILITARY DATA
Satellite information on incoming meteors is blocked.
Geoff Brumfiel, Nature, 12 June 2009
The US military has abruptly ended an informal arrangement that allowed scientists access to data on incoming meteors from classified surveillance satellites. The change is a blow to the astronomers and planetary scientists who used the information to track space rocks, especially those that burn up over the oceans or in other remote locations. "These systems are extremely useful," says Peter Brown, an astronomer at the University of Western Ontario in London, Canada. "I think the scientific community benefited enormously."
When the policy changed is unclear. The website Space.com reported the end of the relationship on 10 June, but Brown says that he was told at the beginning of this year that there would be no further data releases. Mark Boslough, a physicist at Sandia National Laboratories in Albuquerque, New Mexico, says he was told this spring that he could no longer publicly discuss the classified data to which he had some access. Neither scientist could give a reason for the end of the arrangement, and the United States Air Force, which operates the satellites, did not respond in time for Nature's deadline. The Air Force did issue a 16 March memo on the military classification of fireball data, but Nature could not confirm its contents.
The Defense Support Program satellite network is part of the Pentagon's early-warning system. Since 1970, 23 infrared satellites in the series have been launched into geosynchronous orbit to monitor the globe for missile launches or atmospheric nuclear blasts.
But the same infrared sensors were perfect for spotting fireballs as they streaked across the atmosphere, according to Brian Weeden, a former Air Force captain who now works at the Secure World Foundation, a non-profit organization based in Superior, Colorado. The satellites could precisely detect the time, position, altitude and brightness of meteors as they entered Earth's atmosphere. Weeden, who left the Air Force in 2007, says that the military didn't consider that information particularly useful, or classified. "It was being dropped on the floor," he says.
Under an informal arrangement, at least some of the data seem to have been provided on an ad-hoc basis to scientists studying meteorites. Often it came in the form of an anonymous, tersely worded e-mail describing the coordinates, altitude and size of a fireball. Brown, who has collected the data since 1994, declined to specify who sent the reports.
Even the short descriptions of events were enormously helpful. In 2002, Brown and his colleagues used a larger data set from the satellites to quantify the number of objects striking Earth each year (P. Brown et al. Nature 420, 294-296; 2002). Last year, they were used to narrow the search for remnants of the asteroid 2008 TC3 in the Sahara Desert in North Africa, and they were also crucial in recovering a meteorite fragment in 2000 from Tagish Lake in northern Canada. "In both of those cases it's hard to say whether this would have been picked up without the satellite data," Boslough says.
The data also provide a useful check against ground-based instruments monitoring low-frequency sound waves and dust from the fireball explosions, says Brown.
Brown says that whatever the reason, the end of the relationship has left the tight-knit meteorite community smarting. The global reach of the satellites and the data they supplied were unparalleled, he says. "There's nothing else that even comes close," he says.
============================
GERMAN BOY (NOT) HIT BY METEORITE
There has been considerable Internet chatter about a claim that a 14-year-old boy in Essen, Germany, was knocked off his bicycle by a small meteorite. There were no other witnesses, but his story was apparently believed at least locally in Germany, and it has spread widely. The "facts" as reported are almost entirely wrong. However, we do not know what actually happened, or whether the implausible accounts come from the boy or local reporters. Much of the following information is from the Discover-Badastronomy website of Phil Plait (blogs.discovermagazine.com/badastronomy/2009/06/12/a-boy-claims-he-was-hit-by-a-meteorite/).
The original English-language story is from the Telegraph in UK (www.telegraph.co.uk/scienceandtechnology/science/space/5511619/14-year-old-hit-by-30000-mph-space-meteorite.html). They wrote:
Gerrit Blank, 14, was on his way to school when he saw "ball of light" heading straight towards him from the sky. A red hot, pea-sized piece of rock then hit his hand before bouncing off and causing a foot wide crater in the ground. The teenager survived the strike, the chances of which are just 1 in a million - but with a nasty three-inch long scar on his hand.
He said: "At first I just saw a large ball of light, and then I suddenly felt a pain in my hand. Then a split second after that there was an enormous bang like a crash of thunder. The noise that came after the flash of light was so loud that my ears were ringing for hours afterwards. When it hit me it knocked me flying and then was still going fast enough to bury itself into the road," he explained.
Scientists are now studying the pea-sized meteorite which crashed to Earth in Essen, Germany. Chemical tests on the rock have proved it had fallen from space. Ansgar Kortem, director of Germany's Walter Hohmann Observatory, said: "It's a real meteorite, therefore it is very valuable to collectors and scientists."
What are we to make of this? Most of the "facts" don't bear close examination. The "meteorite" is pea sized and looks like a small piece of gravel. If it is a meteorite, it must have been the product of the explosion/disintegration of a larger meteor many kilometers high (since small meteorites can't make it through the atmosphere). It would have reached the ground at terminal velocity (which is low for a pea-size rock) several minutes after the high-altitude explosion. Such a small stone could not make a crater or do any damage to a paved street. It would also have been cool (it would quickly equilibrate with the air it was falling through). Compare this with the story reported in the newspapers:
Speed 30,000 mph - impossible (unless they mean the entry speed)
Red-hot - impossible
Brilliant fireball coming straight toward the boy - impossible
Loud sound at time it hit - impossible
Burned hand - not from the meteorite
Crater in road - not supported by photos
The question of whether this was a real meteorite apparently is also open. A writer to the badastronomy blog wrote: "I just checked the German sites reporting this. Ansgar Korte is quoted as saying “Ist es tatsächlich ein echter Meteorit, dann hat das Exemplar sogar einen gewissen Wert für Sammler und Mineralogen." That would correctly be translated to "IF it is a real meteorite, it would have a certain value for collectors and mineralogists." In any case, a pea-sized meteorite is easily purchased (and inexpensive) if someone wanted to fabricate a hoax.
I have no clue where the fault is, but I recommend skepticism in accepting this story as evidence of a person being hit directly by a meteorite.
David Morrison
============================
ARECIBO SUPPORT
Rusty Schweickart reports the following note from the AAAS public policy blog, quoting from the recent U.S. House Appropriations bill providing FY10 funding for NASA:
Near Earth object observations -- The recommendation includes $5,800,000 for near Earth object observations, an increase of $2,000,000 to support ongoing scientific research at the Arecibo Observatory in the fields of climate change and space weather...
The fact that this item is listed under NEOs suggests that the members of Congress may intend this as operating support for the Arecibo planetary radar, which has been so valuable in studying both the orbits and the physical characteristics of NEOs. However, the underlying issue of the continued operations of the entire Arecibo Observatory, which is managed and funded by the National Science Foundation, does not seem to be addressed in this section of the Appropriations bill.
Stay tuned Š.
==============================
SUMMER DISASTER MOVIE "IMPACT"
An ABC-TV mini-series called "Impact" will be broadcast in the U.S. on June 21. You will find the trailer and some comments on the Badastronomy website at (blogs.discovermagazine.com/badastronomy/2009/06/15/if-i-watch-this-i-hope-the-moon-will-hit-the-earth/).
The movie plot seems to be that a giant meteor storm hits the Moon, excavating huge rocks (bigger than mountains) that rain down on Earth. Then comes the bad part. The meteors contained a "piece of a brown dwarf" which is embedded in the Moon and has increased its mass to twice the mass of the Earth (perhaps they were thinking of a white dwarf, which is extremely dense, not a brown dwarf). Apparently this produced an increase in gravitational mass but not inertial mass (another miracle of nature) because the Moon is now headed for a collision with the Earth. If you care about the outcome, you will need to watch the film.
===============================
FALL DISASTER MOVIE "2012"
Stories about the fictional planet Nibiru and its collision with Earth in December 2012 have blossomed on the Internet. Claims about a 2012 doomsday are the theme of a new from Columbia Pictures titled "2012", to be released in November 2009. Apparently cosmic impacts are a part of the plot.
The film's trailer, appearing in theaters and on their website, shows a tidal wave breaking over the Himalayas, with only the following words: "How would the governments of our planet prepare 6 billion people for the end of the world? [long pause] They wouldn't. [long pause] Find out the Truth. Google search 2012".
The film publicity includes creation of a faux scientific website (www.instituteforhumancontinuity.org/) for "The Institute for Human Continuity", which is entirely fictitious. According to this website, the IHC is dedicated to scientific research and public preparedness. Its mission is the survival of mankind. The website explains that the Institute was founded 1978, and in 2004 IHC scientists confirmed with 94% certainty that the world would be destroyed in 2012. This website encourages people to register for a lottery to select those who will be saved. I learned from Wikipedia that this sort of fake website is a new advertising technique called "Viral Marketing", by analogy with computer viruses.
For lots more information on the Nibiru and 2012 hoaxes see (astrobiology.nasa.gov/ask-an-astrobiologist/intro/nibiru-and-doomsday-2012-questions-and-answers). For the film, we will have to wait until late November.
--
+++++++++++++++++++++++++++++++++++++++++++
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 (06/18/09) Summer Stories
This edition of NEO news is devoted to several current stories that are creating some press and public interest. Some are serious, others are just summer madness. In any case, it is perhaps useful that we be aware of these issues.
David Morrison
=======================
SURVEILLANCE SATELLITE DATA ON BRIGHT FIREBALLS
As first discussed a week ago in an article by Leonard David on Space.com, there is a move to stop releasing the routine observations of large fireballs that have been made by U.S. surveillance satellites. Peter Brown at University of Western Ontario and others have made good use of these data to define the impact frequency for objects in the meter size range and to help locate meteorite falls such as Tagish Lake. This is a serious issue, although some news sources are greatly exaggerating by claiming that the absence of global fireball data somehow increases public risk from impacts. Unfortunately, this topic feeds those who are already paranoid about government secrecy. Following is a sober summary of the issues from Nature on-line:
ASTRONOMERS LOSE ACCESS TO MILITARY DATA
Satellite information on incoming meteors is blocked.
Geoff Brumfiel, Nature, 12 June 2009
The US military has abruptly ended an informal arrangement that allowed scientists access to data on incoming meteors from classified surveillance satellites. The change is a blow to the astronomers and planetary scientists who used the information to track space rocks, especially those that burn up over the oceans or in other remote locations. "These systems are extremely useful," says Peter Brown, an astronomer at the University of Western Ontario in London, Canada. "I think the scientific community benefited enormously."
When the policy changed is unclear. The website Space.com reported the end of the relationship on 10 June, but Brown says that he was told at the beginning of this year that there would be no further data releases. Mark Boslough, a physicist at Sandia National Laboratories in Albuquerque, New Mexico, says he was told this spring that he could no longer publicly discuss the classified data to which he had some access. Neither scientist could give a reason for the end of the arrangement, and the United States Air Force, which operates the satellites, did not respond in time for Nature's deadline. The Air Force did issue a 16 March memo on the military classification of fireball data, but Nature could not confirm its contents.
The Defense Support Program satellite network is part of the Pentagon's early-warning system. Since 1970, 23 infrared satellites in the series have been launched into geosynchronous orbit to monitor the globe for missile launches or atmospheric nuclear blasts.
But the same infrared sensors were perfect for spotting fireballs as they streaked across the atmosphere, according to Brian Weeden, a former Air Force captain who now works at the Secure World Foundation, a non-profit organization based in Superior, Colorado. The satellites could precisely detect the time, position, altitude and brightness of meteors as they entered Earth's atmosphere. Weeden, who left the Air Force in 2007, says that the military didn't consider that information particularly useful, or classified. "It was being dropped on the floor," he says.
Under an informal arrangement, at least some of the data seem to have been provided on an ad-hoc basis to scientists studying meteorites. Often it came in the form of an anonymous, tersely worded e-mail describing the coordinates, altitude and size of a fireball. Brown, who has collected the data since 1994, declined to specify who sent the reports.
Even the short descriptions of events were enormously helpful. In 2002, Brown and his colleagues used a larger data set from the satellites to quantify the number of objects striking Earth each year (P. Brown et al. Nature 420, 294-296; 2002). Last year, they were used to narrow the search for remnants of the asteroid 2008 TC3 in the Sahara Desert in North Africa, and they were also crucial in recovering a meteorite fragment in 2000 from Tagish Lake in northern Canada. "In both of those cases it's hard to say whether this would have been picked up without the satellite data," Boslough says.
The data also provide a useful check against ground-based instruments monitoring low-frequency sound waves and dust from the fireball explosions, says Brown.
Brown says that whatever the reason, the end of the relationship has left the tight-knit meteorite community smarting. The global reach of the satellites and the data they supplied were unparalleled, he says. "There's nothing else that even comes close," he says.
============================
GERMAN BOY (NOT) HIT BY METEORITE
There has been considerable Internet chatter about a claim that a 14-year-old boy in Essen, Germany, was knocked off his bicycle by a small meteorite. There were no other witnesses, but his story was apparently believed at least locally in Germany, and it has spread widely. The "facts" as reported are almost entirely wrong. However, we do not know what actually happened, or whether the implausible accounts come from the boy or local reporters. Much of the following information is from the Discover-Badastronomy website of Phil Plait (blogs.discovermagazine.com/badastronomy/2009/06/12/a-boy-claims-he-was-hit-by-a-meteorite/).
The original English-language story is from the Telegraph in UK (www.telegraph.co.uk/scienceandtechnology/science/space/5511619/14-year-old-hit-by-30000-mph-space-meteorite.html). They wrote:
Gerrit Blank, 14, was on his way to school when he saw "ball of light" heading straight towards him from the sky. A red hot, pea-sized piece of rock then hit his hand before bouncing off and causing a foot wide crater in the ground. The teenager survived the strike, the chances of which are just 1 in a million - but with a nasty three-inch long scar on his hand.
He said: "At first I just saw a large ball of light, and then I suddenly felt a pain in my hand. Then a split second after that there was an enormous bang like a crash of thunder. The noise that came after the flash of light was so loud that my ears were ringing for hours afterwards. When it hit me it knocked me flying and then was still going fast enough to bury itself into the road," he explained.
Scientists are now studying the pea-sized meteorite which crashed to Earth in Essen, Germany. Chemical tests on the rock have proved it had fallen from space. Ansgar Kortem, director of Germany's Walter Hohmann Observatory, said: "It's a real meteorite, therefore it is very valuable to collectors and scientists."
What are we to make of this? Most of the "facts" don't bear close examination. The "meteorite" is pea sized and looks like a small piece of gravel. If it is a meteorite, it must have been the product of the explosion/disintegration of a larger meteor many kilometers high (since small meteorites can't make it through the atmosphere). It would have reached the ground at terminal velocity (which is low for a pea-size rock) several minutes after the high-altitude explosion. Such a small stone could not make a crater or do any damage to a paved street. It would also have been cool (it would quickly equilibrate with the air it was falling through). Compare this with the story reported in the newspapers:
Speed 30,000 mph - impossible (unless they mean the entry speed)
Red-hot - impossible
Brilliant fireball coming straight toward the boy - impossible
Loud sound at time it hit - impossible
Burned hand - not from the meteorite
Crater in road - not supported by photos
The question of whether this was a real meteorite apparently is also open. A writer to the badastronomy blog wrote: "I just checked the German sites reporting this. Ansgar Korte is quoted as saying “Ist es tatsächlich ein echter Meteorit, dann hat das Exemplar sogar einen gewissen Wert für Sammler und Mineralogen." That would correctly be translated to "IF it is a real meteorite, it would have a certain value for collectors and mineralogists." In any case, a pea-sized meteorite is easily purchased (and inexpensive) if someone wanted to fabricate a hoax.
I have no clue where the fault is, but I recommend skepticism in accepting this story as evidence of a person being hit directly by a meteorite.
David Morrison
============================
ARECIBO SUPPORT
Rusty Schweickart reports the following note from the AAAS public policy blog, quoting from the recent U.S. House Appropriations bill providing FY10 funding for NASA:
Near Earth object observations -- The recommendation includes $5,800,000 for near Earth object observations, an increase of $2,000,000 to support ongoing scientific research at the Arecibo Observatory in the fields of climate change and space weather...
The fact that this item is listed under NEOs suggests that the members of Congress may intend this as operating support for the Arecibo planetary radar, which has been so valuable in studying both the orbits and the physical characteristics of NEOs. However, the underlying issue of the continued operations of the entire Arecibo Observatory, which is managed and funded by the National Science Foundation, does not seem to be addressed in this section of the Appropriations bill.
Stay tuned Š.
==============================
SUMMER DISASTER MOVIE "IMPACT"
An ABC-TV mini-series called "Impact" will be broadcast in the U.S. on June 21. You will find the trailer and some comments on the Badastronomy website at (blogs.discovermagazine.com/badastronomy/2009/06/15/if-i-watch-this-i-hope-the-moon-will-hit-the-earth/).
The movie plot seems to be that a giant meteor storm hits the Moon, excavating huge rocks (bigger than mountains) that rain down on Earth. Then comes the bad part. The meteors contained a "piece of a brown dwarf" which is embedded in the Moon and has increased its mass to twice the mass of the Earth (perhaps they were thinking of a white dwarf, which is extremely dense, not a brown dwarf). Apparently this produced an increase in gravitational mass but not inertial mass (another miracle of nature) because the Moon is now headed for a collision with the Earth. If you care about the outcome, you will need to watch the film.
===============================
FALL DISASTER MOVIE "2012"
Stories about the fictional planet Nibiru and its collision with Earth in December 2012 have blossomed on the Internet. Claims about a 2012 doomsday are the theme of a new from Columbia Pictures titled "2012", to be released in November 2009. Apparently cosmic impacts are a part of the plot.
The film's trailer, appearing in theaters and on their website, shows a tidal wave breaking over the Himalayas, with only the following words: "How would the governments of our planet prepare 6 billion people for the end of the world? [long pause] They wouldn't. [long pause] Find out the Truth. Google search 2012".
The film publicity includes creation of a faux scientific website (www.instituteforhumancontinuity.org/) for "The Institute for Human Continuity", which is entirely fictitious. According to this website, the IHC is dedicated to scientific research and public preparedness. Its mission is the survival of mankind. The website explains that the Institute was founded 1978, and in 2004 IHC scientists confirmed with 94% certainty that the world would be destroyed in 2012. This website encourages people to register for a lottery to select those who will be saved. I learned from Wikipedia that this sort of fake website is a new advertising technique called "Viral Marketing", by analogy with computer viruses.
For lots more information on the Nibiru and 2012 hoaxes see (astrobiology.nasa.gov/ask-an-astrobiologist/intro/nibiru-and-doomsday-2012-questions-and-answers). For the film, we will have to wait until late November.
--
+++++++++++++++++++++++++++++++++++++++++++
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.
05 June 2009
NEO News (06/04/09) Planetary Defense at Granada pt 2
From Dave Morrison.
NEO News (06/04/09) Planetary Defense at Granada pt 2
The edition of NEO News is a continuation of my last message, which was sent 05/29/09.The focus here is on international political support, as well as technical issues associated with protecting our planet from asteroid impacts. A future message will summarize the conclusions and recommendations from the conference.
David Morrison
========================
INTERNATIONAL ORGANIZATIONS AND STUDIES
The International Academy of Astronautics was the primary sponsor of this planetary defense conference, which was held April 27-30 in Granada, Spain. Jean-Michel Contant welcomed the attendees on behalf of the IAA and committed the organization to support future Planetary Defense Conferences at two-year intervals. The next meeting will be in Bucharest, Romania, on May 9-14, 2011.
The IAA has recently completed its own study of the impact threat, summarized at this meeting by Ivan Bekey, called "Dealing with the Threat to Earth from Asteroids and Comets" (2009, 140 pages). The abstract of this document says "The Earth has been struck by asteroids and comets many times throughout its history. This report of the International Academy of Astronautics addresses the nature of the threat, expected future impacts, and the consequences of impacts from various size NEOs. It reviews current programs to detect, track, and characterize NEOs, and the future improvements required in order to take responsible and timely action. It identifies a number of techniques that could alter an incoming NEO's orbit so as to avoid an impact. It addresses the organizational aspects that will have to be dealt with if a serious international capability is to be developed and employed to mitigate the threat. It then addresses behavioral factors and the sociological and psychological aspects of the threat and attempts at its mitigation before, during, and after an intercept attempt, whether successful or not. Lastly the report examines some of the principal international policy implications that must be dealt with if the world is to act in a timely, unified, and effective way with the very real threat due to NEOs." To access full text go to this website: http://iaaweb.org/content/view/229/356/. The report contains useful information, but since it was 4 years in preparation, parts of it are rather dated.
D. Koschny of ESA (the European Space Agency) reported on an initiative to include asteroid impacts within the European Space Situational Awareness Programme. Situational awareness is concerned with perception of the environment critical to decision-makers in complex, dynamic areas such as aviation, air traffic control, and military command and control. The objective of the European Space Situational Awareness initiative is to support the European independent utilization of and access to space for research or services, through providing timely and quality data, information, services and knowledge regarding the environment, the threats, and the sustainable exploitation of the outer space. The components of this initiative are space surveillance, space weather, and NEOs. For NEOs, they intend to study tracking, orbit determination, orbital databases, and identification of impact risks. The main objective is to issue impact warnings. They intend to provide information on the impact probability and/or miss distance of NEOs. To do this, they will assess impact analyses and perform their own risk assessments.
As these are all tasks that are already being addressed by the NASA NEO Program, the initial ESA activity may be to transmit this information to European decision-makers. No independent European detection or orbital analysis plans were suggested.
Rusty Schweickart provided an update to this meeting on the "Call for Global Response" of the international panel on Asteroid Threat Mitigation of the Association of Space Explorers (made up of astronauts and cosmonauts who have flown in space). Their report has been submitted to the UN committee on the Peaceful uses of Outer Space (COPUOS) and is currently entering a process of deliberation and potential action within the UN. We will be reporting on it in the future.
UNITED STATES STUDIES AND PLANS
Mike A'Hearn of the University of Maryland summarized the current study of the NEO Hazard being carried out by the National Research Council of the National Academy of Sciences. This study, chaired by Irwin Shapiro, the Director emeritus of the Harvard College Observatory, is primarily addressing requests from Congress. They are considering the challenge of surveying potentially hazardous NEAs at smaller sizes, to reach 90% completeness at a diameter of 140 m. They are also considering a wide variety of techniques for characterization and mitigation. Congressional staff members have told the NAS-NRC steering committee that the Congress is interested in understanding how international collaboration should work in this area. This NRC study and recommendations should be completed at the end of 2009.
The capabilities of two large ground-based survey projects were
discussed: Pan-STARRS presented by M. Granvik (with the first of four survey telescopes near completion in Hawaii, funded by the U.S. Air Force), and LSST presented by Z. Ivezic (a single wide-field 8-m telescope to be constructed in Chile, with detailed studies underway supported by the U.S. National Science Foundation and the U.S.
Department of Energy). Space-based asteroid detection in the thermal infrared was discussed by Amy Mainzer of JPL, who described the capabilities of WISE (the NASA Widefield Infrared Survey Explorer), which is to be launched in November 2009, and of a possible dedicated infrared NEA survey called NEO-CAM to follow.
Peter Garretson (Lt. Col., US Air Force) reported the results of a scripted multi-agency deflection and disaster exercise. Participants included middle-level representatives of U.S. Air Force, NASA, National Security Council, Department of Defense, Department of State, Department of Homeland Security, Navy, Coast Guard, Federal Emergency Management Agency, and Defense Threat Reduction Agency. The objective was to better understand how responsible government organs would respond in the absence of clear policy on roles and missions.
The table-top simulation involved two specific threats: a binary asteroid the size of Apophis targeted in the Atlantic Ocean off the coast of Nigeria, and a 50-m metallic asteroid targeted on the Eastern U.S. near Washington DC. They studied possible mitigation of the ocean impact given 7 years warning, and disaster management for the U.S. impact given 72 hours warning. The participants were aware of lack of previous planning. While a number of useful analogs exist, as well as procedures that could be used or adapted, attempts or do so in the moment are likely to be much less successful than advance preparation. Participants recommended that the NEO scenario should be elevated to higher levels with more senior players. They also concluded that proper planning and response to a NEO emergency requires delineation of organizational responsibilities including lead agency and notification standards, but they were not able to agree on which should be the lead agency. This was the first time such a multi-agency exercise had taken place in the U.S. Dealing with similar issues on an international scale would be even more problematic.
NEA CHARACTERIZATION
Lance Benner (JPL) provided an update on the always-spectacular discoveries using the Arecibo and Goldstone radars, which are our most powerful tools for both orbital and physical characterization of NEAs (if they come with radar range). He showed an interesting comparison between the radar and spacecraft images of Itokawa; the radar got the size and shape right but could not resolve the fine detail, including the many boulders on the surface. Among the newly imaged objects were 1992 UY4, 1998 CS1, and the binary NEA 2000 DP107. Radar data indicate that about 10% of NEAs are actually contact binaries, and he stressed how different NEAs are, with "no such thing as a typical NEA."
Rick Binzel (MIT) reviewed telescopic data on the physical properties of NEAs. Large telescopes are being used to obtain visible and near-infrared colors, spectrophotometry, and polarimetry. He introduced a more accurate classification of 42-channel spectrophotometry to create what he calls the Bus-DeMeo taxonomy, with more than 20 classes. Reminding the audience that we have thousands of direct samples of NEAs in the form of meteorites, Binzel noted that one of the objectives of telescopic studies is to link the remote measurements of NEA spectra with specific meteorite types. He used such an analysis to conclude that Apophis has the surface composition of a LL Chondrite. If this is correct, we can use lab study of meteorites to estimate that Apophis is composed primarily of olivine and pyroxene with relatively low metal content. The bulk density of this material is 3.2 g/cc. Similar telescopic data for
2008 TC3 can be calibrated from the recovered meteorites. Binzel called this classification of NEAs from telescopic data "our first line of defense against NEOs."
The use of small spacecraft for detailed physical characterization of NEAs was the subject of several presentations and poster papers. The Japanese Hayabusa mission to Itokawa is an outstanding example of this approach. David Morrison stressed that flybys are of little use for small NEA targets, with a rendezvous required to determine such key properties as mass, density, and surface topography. He described a low-cost mission called MAAT that has been studied at NASA Ames Research Center. Another paper described the Didymos explorer mission designed to explore a binary NEA. Another proposed Apophis mission called Foresight is intended to tag Apophis with a radio transponder for very precise orbit determination, and PROBA-IP is an ESA technology demonstration mission targeted to Apophis. There was considerable discussion of the great value of a combined rendezvous and ballistic impact mission. Such a mission called Don Quijote was studied by ESA but now seems to have been dropped. However, ESA is working with Japan on an alternative NEA rendezvous mission without the impactor.
MORRISON COMMENTARY ON THE CONFERENCE
This was an excellent meeting: well attended and with some fine technical and policy papers presented. Most of the leaders in the NEO defense arena were present, as well as many new participants, especially many young scientists from Europe.
Several speakers assumed that the current estimates of the impact rate are greater than previously thought, adding urgency to this threat. Judging by some of the presentations at this meeting, these assessments were based on faulty or misinterpreted data. As Al Harris (Space Science Institute) showed (discussed in NEO News 05/29/09), at least 90% of the risk associated with impact by an unknown asteroid has been eliminated by the Spaceguard Survey, and in addition the NEO population data summarized by Harris indicate fewer sub-km asteroids by at least a factor of 2, relative to previous power-law estimates.
It is curious to see claims by policy analysts that the impact threat is increasing while the scientific community comes to the opposite conclusion.
There was thus a certain unreality about some of the discussions.
Many international and European organizations are becoming concerned about the impact hazard just at the time it is being rapidly reduced by the Spaceguard Survey. While there have been some excellent paper studies (for example, the U.K. impact hazard study in 2001), so far only two nations have made significant contributions to actually mitigating the impact hazard: the United States and Japan. The U.S.
has financed the Spaceguard survey, the Minor Planet Center, the NEO Program Office at JPL, the planetary radar systems at Arecibo and Goldstone, studies of the next generation of survey telescopes (including construction of the Pan-STARRS-1, casting the 8-m mirror for the LSST, building the WISE infrared survey satellite, and sending the NEAR-Shoemaker mission which orbited and landed on Eros).
Japan has carried out the only spacecraft study of a sub-km NEA, Itokawa, including brief landing and collection of a sample now en route back to Earth.
Three surprising new results presented at this meeting stand out in my mind. (1) The strange case of the Carancas meteorite fall on the Altiplano at the Peru-Bolivia border on September 15, 2007, which was described by Tancredi. A stony (ordinary chondrite) meteorite with an original mass of a few tons hit at a few km/s speed and formed a 15-m wide crater. This should not happen according to conventional models.
(2) Boslough's supercomputer simulations of the Tunguska impact indicate that stony objects <40m in diameter can produce highly destructive airbursts, and somewhat larger airbursts can also generate substantial melting of silicates at the surface when their fireball reaches the ground. (3) The unique case of 2008 TC3 showed that even with the current survey systems it is possible to detect a small NEA very close to impact, accurately predict the impact time and place, and recover meteorites. This is also our first chance to directly compare remote sensing observations of the parent object in space with "ground truth" from recovered samples. TC3 has greatly increased interest in detection of small asteroids within a few days of impact.
--
+++++++++++++++++++++++++++++++++++++++++++
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 david.morrison@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 (06/04/09) Planetary Defense at Granada pt 2
The edition of NEO News is a continuation of my last message, which was sent 05/29/09.The focus here is on international political support, as well as technical issues associated with protecting our planet from asteroid impacts. A future message will summarize the conclusions and recommendations from the conference.
David Morrison
========================
INTERNATIONAL ORGANIZATIONS AND STUDIES
The International Academy of Astronautics was the primary sponsor of this planetary defense conference, which was held April 27-30 in Granada, Spain. Jean-Michel Contant welcomed the attendees on behalf of the IAA and committed the organization to support future Planetary Defense Conferences at two-year intervals. The next meeting will be in Bucharest, Romania, on May 9-14, 2011.
The IAA has recently completed its own study of the impact threat, summarized at this meeting by Ivan Bekey, called "Dealing with the Threat to Earth from Asteroids and Comets" (2009, 140 pages). The abstract of this document says "The Earth has been struck by asteroids and comets many times throughout its history. This report of the International Academy of Astronautics addresses the nature of the threat, expected future impacts, and the consequences of impacts from various size NEOs. It reviews current programs to detect, track, and characterize NEOs, and the future improvements required in order to take responsible and timely action. It identifies a number of techniques that could alter an incoming NEO's orbit so as to avoid an impact. It addresses the organizational aspects that will have to be dealt with if a serious international capability is to be developed and employed to mitigate the threat. It then addresses behavioral factors and the sociological and psychological aspects of the threat and attempts at its mitigation before, during, and after an intercept attempt, whether successful or not. Lastly the report examines some of the principal international policy implications that must be dealt with if the world is to act in a timely, unified, and effective way with the very real threat due to NEOs." To access full text go to this website: http://iaaweb.org/content/view/229/356/. The report contains useful information, but since it was 4 years in preparation, parts of it are rather dated.
D. Koschny of ESA (the European Space Agency) reported on an initiative to include asteroid impacts within the European Space Situational Awareness Programme. Situational awareness is concerned with perception of the environment critical to decision-makers in complex, dynamic areas such as aviation, air traffic control, and military command and control. The objective of the European Space Situational Awareness initiative is to support the European independent utilization of and access to space for research or services, through providing timely and quality data, information, services and knowledge regarding the environment, the threats, and the sustainable exploitation of the outer space. The components of this initiative are space surveillance, space weather, and NEOs. For NEOs, they intend to study tracking, orbit determination, orbital databases, and identification of impact risks. The main objective is to issue impact warnings. They intend to provide information on the impact probability and/or miss distance of NEOs. To do this, they will assess impact analyses and perform their own risk assessments.
As these are all tasks that are already being addressed by the NASA NEO Program, the initial ESA activity may be to transmit this information to European decision-makers. No independent European detection or orbital analysis plans were suggested.
Rusty Schweickart provided an update to this meeting on the "Call for Global Response" of the international panel on Asteroid Threat Mitigation of the Association of Space Explorers (made up of astronauts and cosmonauts who have flown in space). Their report has been submitted to the UN committee on the Peaceful uses of Outer Space (COPUOS) and is currently entering a process of deliberation and potential action within the UN. We will be reporting on it in the future.
UNITED STATES STUDIES AND PLANS
Mike A'Hearn of the University of Maryland summarized the current study of the NEO Hazard being carried out by the National Research Council of the National Academy of Sciences. This study, chaired by Irwin Shapiro, the Director emeritus of the Harvard College Observatory, is primarily addressing requests from Congress. They are considering the challenge of surveying potentially hazardous NEAs at smaller sizes, to reach 90% completeness at a diameter of 140 m. They are also considering a wide variety of techniques for characterization and mitigation. Congressional staff members have told the NAS-NRC steering committee that the Congress is interested in understanding how international collaboration should work in this area. This NRC study and recommendations should be completed at the end of 2009.
The capabilities of two large ground-based survey projects were
discussed: Pan-STARRS presented by M. Granvik (with the first of four survey telescopes near completion in Hawaii, funded by the U.S. Air Force), and LSST presented by Z. Ivezic (a single wide-field 8-m telescope to be constructed in Chile, with detailed studies underway supported by the U.S. National Science Foundation and the U.S.
Department of Energy). Space-based asteroid detection in the thermal infrared was discussed by Amy Mainzer of JPL, who described the capabilities of WISE (the NASA Widefield Infrared Survey Explorer), which is to be launched in November 2009, and of a possible dedicated infrared NEA survey called NEO-CAM to follow.
Peter Garretson (Lt. Col., US Air Force) reported the results of a scripted multi-agency deflection and disaster exercise. Participants included middle-level representatives of U.S. Air Force, NASA, National Security Council, Department of Defense, Department of State, Department of Homeland Security, Navy, Coast Guard, Federal Emergency Management Agency, and Defense Threat Reduction Agency. The objective was to better understand how responsible government organs would respond in the absence of clear policy on roles and missions.
The table-top simulation involved two specific threats: a binary asteroid the size of Apophis targeted in the Atlantic Ocean off the coast of Nigeria, and a 50-m metallic asteroid targeted on the Eastern U.S. near Washington DC. They studied possible mitigation of the ocean impact given 7 years warning, and disaster management for the U.S. impact given 72 hours warning. The participants were aware of lack of previous planning. While a number of useful analogs exist, as well as procedures that could be used or adapted, attempts or do so in the moment are likely to be much less successful than advance preparation. Participants recommended that the NEO scenario should be elevated to higher levels with more senior players. They also concluded that proper planning and response to a NEO emergency requires delineation of organizational responsibilities including lead agency and notification standards, but they were not able to agree on which should be the lead agency. This was the first time such a multi-agency exercise had taken place in the U.S. Dealing with similar issues on an international scale would be even more problematic.
NEA CHARACTERIZATION
Lance Benner (JPL) provided an update on the always-spectacular discoveries using the Arecibo and Goldstone radars, which are our most powerful tools for both orbital and physical characterization of NEAs (if they come with radar range). He showed an interesting comparison between the radar and spacecraft images of Itokawa; the radar got the size and shape right but could not resolve the fine detail, including the many boulders on the surface. Among the newly imaged objects were 1992 UY4, 1998 CS1, and the binary NEA 2000 DP107. Radar data indicate that about 10% of NEAs are actually contact binaries, and he stressed how different NEAs are, with "no such thing as a typical NEA."
Rick Binzel (MIT) reviewed telescopic data on the physical properties of NEAs. Large telescopes are being used to obtain visible and near-infrared colors, spectrophotometry, and polarimetry. He introduced a more accurate classification of 42-channel spectrophotometry to create what he calls the Bus-DeMeo taxonomy, with more than 20 classes. Reminding the audience that we have thousands of direct samples of NEAs in the form of meteorites, Binzel noted that one of the objectives of telescopic studies is to link the remote measurements of NEA spectra with specific meteorite types. He used such an analysis to conclude that Apophis has the surface composition of a LL Chondrite. If this is correct, we can use lab study of meteorites to estimate that Apophis is composed primarily of olivine and pyroxene with relatively low metal content. The bulk density of this material is 3.2 g/cc. Similar telescopic data for
2008 TC3 can be calibrated from the recovered meteorites. Binzel called this classification of NEAs from telescopic data "our first line of defense against NEOs."
The use of small spacecraft for detailed physical characterization of NEAs was the subject of several presentations and poster papers. The Japanese Hayabusa mission to Itokawa is an outstanding example of this approach. David Morrison stressed that flybys are of little use for small NEA targets, with a rendezvous required to determine such key properties as mass, density, and surface topography. He described a low-cost mission called MAAT that has been studied at NASA Ames Research Center. Another paper described the Didymos explorer mission designed to explore a binary NEA. Another proposed Apophis mission called Foresight is intended to tag Apophis with a radio transponder for very precise orbit determination, and PROBA-IP is an ESA technology demonstration mission targeted to Apophis. There was considerable discussion of the great value of a combined rendezvous and ballistic impact mission. Such a mission called Don Quijote was studied by ESA but now seems to have been dropped. However, ESA is working with Japan on an alternative NEA rendezvous mission without the impactor.
MORRISON COMMENTARY ON THE CONFERENCE
This was an excellent meeting: well attended and with some fine technical and policy papers presented. Most of the leaders in the NEO defense arena were present, as well as many new participants, especially many young scientists from Europe.
Several speakers assumed that the current estimates of the impact rate are greater than previously thought, adding urgency to this threat. Judging by some of the presentations at this meeting, these assessments were based on faulty or misinterpreted data. As Al Harris (Space Science Institute) showed (discussed in NEO News 05/29/09), at least 90% of the risk associated with impact by an unknown asteroid has been eliminated by the Spaceguard Survey, and in addition the NEO population data summarized by Harris indicate fewer sub-km asteroids by at least a factor of 2, relative to previous power-law estimates.
It is curious to see claims by policy analysts that the impact threat is increasing while the scientific community comes to the opposite conclusion.
There was thus a certain unreality about some of the discussions.
Many international and European organizations are becoming concerned about the impact hazard just at the time it is being rapidly reduced by the Spaceguard Survey. While there have been some excellent paper studies (for example, the U.K. impact hazard study in 2001), so far only two nations have made significant contributions to actually mitigating the impact hazard: the United States and Japan. The U.S.
has financed the Spaceguard survey, the Minor Planet Center, the NEO Program Office at JPL, the planetary radar systems at Arecibo and Goldstone, studies of the next generation of survey telescopes (including construction of the Pan-STARRS-1, casting the 8-m mirror for the LSST, building the WISE infrared survey satellite, and sending the NEAR-Shoemaker mission which orbited and landed on Eros).
Japan has carried out the only spacecraft study of a sub-km NEA, Itokawa, including brief landing and collection of a sample now en route back to Earth.
Three surprising new results presented at this meeting stand out in my mind. (1) The strange case of the Carancas meteorite fall on the Altiplano at the Peru-Bolivia border on September 15, 2007, which was described by Tancredi. A stony (ordinary chondrite) meteorite with an original mass of a few tons hit at a few km/s speed and formed a 15-m wide crater. This should not happen according to conventional models.
(2) Boslough's supercomputer simulations of the Tunguska impact indicate that stony objects <40m in diameter can produce highly destructive airbursts, and somewhat larger airbursts can also generate substantial melting of silicates at the surface when their fireball reaches the ground. (3) The unique case of 2008 TC3 showed that even with the current survey systems it is possible to detect a small NEA very close to impact, accurately predict the impact time and place, and recover meteorites. This is also our first chance to directly compare remote sensing observations of the parent object in space with "ground truth" from recovered samples. TC3 has greatly increased interest in detection of small asteroids within a few days of impact.
--
+++++++++++++++++++++++++++++++++++++++++++
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 david.morrison@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.
29 May 2009
NEO News (05/29/09) Planetary Defense at Granada pt 1
From Dave Morrison.
NEO News (05/29/09) Planetary Defense at Granada pt 1
This edition of NEO News provides an overview of the Planetary Defense Conference held in Granada April 27-30, 2009, followed by a more detailed discussion of a few papers. Other reports from this conference will follow in later editions.
David Morrison
===============================
CONFERENCE OUTLINE
This meeting was officially named "Planetary Defense Conference (PDC): Protecting the Earth from Asteroids". It was the first planetary defense conference sponsored by the International Academy of Astronautics, although it follows the pattern of previous conferences sponsored by the American Institute of Aeronautics and Astronautics. As with the previous meetings, this one was organized by William Ailor of The Aerospace Corp, joined this time by co-organizer Richard Tremayne-Smith from the UK. Logistics were handled by ESA (European Space Agency). Approximately 40 oral papers were presented, in addition to a similar number of poster presentations plus several panel discussions.
The PDC sessions covered the following topics: (1) Discovery, Tracking and Characterization of NEAs (a full day session), (2) Mission and Campaign Design, (3) Deflection Technologies and Simulations, (4) Impacts and Consequences, (5) Policy, Preparedness and Deciding to Act, and (6) a concluding summary session. Among the new topics discussed were the experiences of the Japanese Hayabusa mission investigating the sub-km asteroid Itokawa, detailed discussion of the search capability of the proposed Pan-STARRS and LSST telescopes, reports on the Carancas impact event in the Altiplano (September 15, 2007), and reports on the discovery, impact (October 7, 2008), and subsequent recovery of fragments from the small asteroid 2008 TC3. This conference also followed a meeting of lawyers the previous week in Lincoln, Nebraska, considering the legal aspects of planetary protection, as reported by Frans van der Dunk of the University of Nebraska.
Keynote talks were presented by ESA astronaut Pedro Duque (who is from Spain) and Nature editor Oliver Morton (who is about to become an editor of The Economist). Morton provided an interesting journalist's perspective, noting that our interest in defending against celestial dangers marks a fundamental departure from the history of astronomical studies of the cosmos. Through history, astronomy has been the least practical of sciences, and most astronomers and space scientists still think of it that way. It is therefore perhaps no surprise that many traditional astronomers have not accepted or perhaps even grasped the significance of what we are doing toward protection of our planet. Morton also discussed lessons that the development of ideas about planetary protection might offer to other areas of human endeavor, such as global warming. Global warming is another field where technological capability, catastrophic potential, and planetary perspectives coincide.
The next Planetary Defense Conference is to be in Bucharest, Romania, May 9-14, 2011.
IMPLICATIONS OF 2008 TC3
TC3 is the first asteroid to be discovered before impact. The explosion point in northern Sudan was determined with sufficient accuracy to allow later recovery of meteorites. Clark Chapman and Rusty Schweickart of the B612 Foundation discussed some of the ways our new-found ability to detect very small NEAs close to the Earth can change our perspectives. They suggest the importance of coordination of NEA searches with disaster planning and response communities. It may be that even with the current Spaceguard system we are more likely to find a very small NEA just a few days before impact than to find a large one with decades of warning. Chapman noted that little work has been done to identify the smallest NEA that is dangerous, or the smallest that might be of interest to decision-makers. Recent models suggest that the threshold for significant ground damage is 30-40 m. But how would public officials react to a prediction of a 25 m impact, or a 15 m impact? There is about a 20% chance of an impact by a 15 m NEA in this decade. Decisions dealing with small impactors (including those that ultimately miss) may need to be made every few years, if we can predict them. Hyped or unreliable media stories might happen annually.
David Morrison also discussed some of these issues, looking at the historical progression of perspectives on the impact hazard.
1. Assessing the hazard. During the 1990s, the standard scientific tools of sampling and statistical analysis were essential to understand the impact hazard and communicate the risk to decision makers. Clark Chapman and David Morrison first identified the threshold for global damage and estimated the risk from impacts of different size. This early work compared the impact risk to other natural hazards, estimated the risk as a function of NEO size, and laid the foundation for establishing the Spaceguard Survey in 1998. The first Congressional language (in 1991) reflected this perspective when it noted, "the Committee believes it is only prudent to assess the nature of the threatŠ" Note that while these statistical studies provide a tool to analyze various mitigation schemes, they do not in themselves reduce the hazard. The step of moving from a scientific risk-analysis perspective to actually mitigating the impact hazard required a major re-orientation of thinking.
2. Mitigating the Hazard. The public and decision-makers are not interested in a better statistical understanding of the impact threat; they want warning and protection. The public-policy goal is not to refine the estimate of the risk but to identify the next impactor and do something about it. That is the purpose of surveys, orbital calculations, and follow-up characterization. The Spaceguard goal of finding 90% of the NEAs larger than 1 km diameter focuses on NEAs that are large enough to risk a global catastrophe. These are also the impacts that might threaten the survival of civilization. While such impacts are very rare, happening less than once in a million years, they still dominate the risk over more frequent impacts. Future surveys (such as Pan-STARRS and LSST) are also designed to provide decades of warning. The objective is not the last-minute detection of incoming objects, and the surveys have not been optimized for such purposes.
3. Dealing with Public Concerns. Issues that worry the public (and many decision makers) are not necessarily the greatest threats. The very rare large impacts pose the greatest hazards, but most people are more concerned about the next impact (which is likely to be small). 2008 TC3 is an example; too small to pose any danger, but something that would be of substantial public interest if it fell over a populated region. From this perspective, it is the number of "threat warnings" that matters, not the size of the threat. A 20 m object detected this week with one-week warning time will get much more attention than a 2 km object that won't actually threaten an impact for the next century. Ideally we should design a survey system that detects both distant large NEAs and close small ones. But (Morrison argued) if a choice must be made between optimizing for the deep surveys and searching for small impactors near the Earth, then it is more important to maintain the capability of detecting larger NEAs at great distances in deep surveys. The larger asteroids still dominate the hazard. Faced with both a cloud of mosquitoes and a venomous snake, we may be tempted just to go after the numerous mosquitoes, but we ignore the snake at our peril.
DESTRUCTIVE POTENTIAL OF IMPACTS BY SMALL NEAS
As the focus of new searches moves toward smaller (sub-km) NEAs, we are also learning more about the destructive potential of impacts at the smaller end of the NEA size spectrum. Mark Boslough (Sandia National Laboratories) and Galen Gisler (University of Oslo) both have used supercomputer models to investigate airbursts and tsunami formation, respectively.
Boslaugh has been simulating low-altitude airbursts of hypervelocity impacts from NEAs <100 m in diameter, finding an increased damage potential relative to earlier models that did not include the downward momentum of the exploding mass. Fireballs from nuclear explosions rise, but those from an asteroid initially continue downward from the point of disintegration. Because of this downward flow, larger blast waves and stronger thermal radiation pulses are experienced at the surface than would be produced for a nuclear airburst of the same yield. The 1908 Tunguska explosion is an example of an airburst in which the hot jet of vaporized projectile material continued downward but lost momentum before it made contact with the surface. The models suggest that the total energy released in the Tunguska event was not more than 5 megatons, in contrast to earlier analyses that suggested an energy of 10-15 megatons. For somewhat larger impacts, the fireball descends all the way to the ground, where it can melt silicate materials. The mysterious Libyan glass may have been produced by such a fireball.
Gisler (with co-author R. Weaver) did 2-D and 3-D computational analyses of the effects of ocean impacts of NEAs <500 m in diameter. They concluded that the near-field effects (that is, within 100 km of the impact) are the dominant danger, with central jets rising several km into the atmosphere and generating highly non-linear breaking waves that could devastate shorelines. However, the impact does not generate long-distance tsunami-like waves, so the area of damage remains local.
NEO POPULATION AND IMPACT RISK
With the nominal completion of the 10-year Spaceguard Survey focused on NEAs >1 km diameter, it is important to assess where we stand. Alan Harris (Space Science Institute) provided for this conference a re-evaluation of the population of NEAs and an estimate of the remaining risk from impacts. As of January 19, 2009, the present surveys have discovered 765 NEAs larger than 1 km (as estimated from their brightness) out of an estimated total population of 940. This is 81% completeness. Note that these numbers reflect a re-evaluation made a few years ago to the asteroid magnitude scale and the conversion factor from observed magnitudes to diameters, resulting in a fewer NEAs >1 km. Since the survey is more nearly complete at 2 km diameter, which is close to the probable threshold for globally catastrophic impacts, the Spaceguard Survey has actually "retired" more than 90% of the total impact risk. Almost half of all NEAs as large as Apophis have already been discovered, but only a negligible fraction of Tunguska-size NEAs.
As noted above, it now appears that ground damage from airbursts extends to considerably smaller impactor sizes than was previously inferred. The main risk in the size range from 150 m to 1000 m is from tsunamis, but with adequate warning the actual fatalities from tsunamis can be small. Harris re-evaluates the likely casualties using known population distributions and improved estimates of the damage from impacts. With the current level of survey completeness (which includes many sub-km objects as well as larger ones), Harris estimates that the remaining risk from the undiscovered population (expressed as average annual fatalities) is roughly 20/yr from local/regional land impacts, 4/yr from impact tsunamis, and 54/yr from globally catastrophic events (the undiscovered big ones). The next generation surveys, aimed at finding 90% of NEAs >140 m, will further reduce impact risk. Using these models of population, completion, and impact damage, Harris estimates a residual risk of roughly 6/yr from local/regional impacts, <1/yr from impact tsunamis, and 11/yr from globally catastrophic events, plus a continuing background risk of 10/yr from long-period comets.
Harris concluded that within a few years, if not already, we will have found essentially all dangerous asteroids large enough to be a risk of global climatic effects. We will be left with some fractional probability that even one such object remains undiscovered. Mid-size impacts, presenting mainly tsunami risk, are less frequent and probably less damaging than previously estimated. In the smallest size range capable of causing ground damage, the next generation survey may find ~25%, providing long-term warning. Ground-based optical surveys can also be designed with about 25-35% chance of detecting a "death plunge" object, down to the smallest size capable of producing ground damage, providing days to weeks' warning. Thus in a very short time on the scale of civilizations, and even quite short in terms of a human lifetime, the impact hazard should be reduced to a negligible risk. The one exception to this is the risk from long-period comets, for which present technology can offer no protection beyond short-term warning. Fortunately this risk is estimated to be quite small. Harris also noted that it is obvious that doing something about the global catastrophic events is worthwhile by almost any accounting. It is in the smaller size range where more careful cost-benefit accounting is in order to evaluate programs and policies.
--
+++++++++++++++++++++++++++++++++++++++++++
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 (05/29/09) Planetary Defense at Granada pt 1
This edition of NEO News provides an overview of the Planetary Defense Conference held in Granada April 27-30, 2009, followed by a more detailed discussion of a few papers. Other reports from this conference will follow in later editions.
David Morrison
===============================
CONFERENCE OUTLINE
This meeting was officially named "Planetary Defense Conference (PDC): Protecting the Earth from Asteroids". It was the first planetary defense conference sponsored by the International Academy of Astronautics, although it follows the pattern of previous conferences sponsored by the American Institute of Aeronautics and Astronautics. As with the previous meetings, this one was organized by William Ailor of The Aerospace Corp, joined this time by co-organizer Richard Tremayne-Smith from the UK. Logistics were handled by ESA (European Space Agency). Approximately 40 oral papers were presented, in addition to a similar number of poster presentations plus several panel discussions.
The PDC sessions covered the following topics: (1) Discovery, Tracking and Characterization of NEAs (a full day session), (2) Mission and Campaign Design, (3) Deflection Technologies and Simulations, (4) Impacts and Consequences, (5) Policy, Preparedness and Deciding to Act, and (6) a concluding summary session. Among the new topics discussed were the experiences of the Japanese Hayabusa mission investigating the sub-km asteroid Itokawa, detailed discussion of the search capability of the proposed Pan-STARRS and LSST telescopes, reports on the Carancas impact event in the Altiplano (September 15, 2007), and reports on the discovery, impact (October 7, 2008), and subsequent recovery of fragments from the small asteroid 2008 TC3. This conference also followed a meeting of lawyers the previous week in Lincoln, Nebraska, considering the legal aspects of planetary protection, as reported by Frans van der Dunk of the University of Nebraska.
Keynote talks were presented by ESA astronaut Pedro Duque (who is from Spain) and Nature editor Oliver Morton (who is about to become an editor of The Economist). Morton provided an interesting journalist's perspective, noting that our interest in defending against celestial dangers marks a fundamental departure from the history of astronomical studies of the cosmos. Through history, astronomy has been the least practical of sciences, and most astronomers and space scientists still think of it that way. It is therefore perhaps no surprise that many traditional astronomers have not accepted or perhaps even grasped the significance of what we are doing toward protection of our planet. Morton also discussed lessons that the development of ideas about planetary protection might offer to other areas of human endeavor, such as global warming. Global warming is another field where technological capability, catastrophic potential, and planetary perspectives coincide.
The next Planetary Defense Conference is to be in Bucharest, Romania, May 9-14, 2011.
IMPLICATIONS OF 2008 TC3
TC3 is the first asteroid to be discovered before impact. The explosion point in northern Sudan was determined with sufficient accuracy to allow later recovery of meteorites. Clark Chapman and Rusty Schweickart of the B612 Foundation discussed some of the ways our new-found ability to detect very small NEAs close to the Earth can change our perspectives. They suggest the importance of coordination of NEA searches with disaster planning and response communities. It may be that even with the current Spaceguard system we are more likely to find a very small NEA just a few days before impact than to find a large one with decades of warning. Chapman noted that little work has been done to identify the smallest NEA that is dangerous, or the smallest that might be of interest to decision-makers. Recent models suggest that the threshold for significant ground damage is 30-40 m. But how would public officials react to a prediction of a 25 m impact, or a 15 m impact? There is about a 20% chance of an impact by a 15 m NEA in this decade. Decisions dealing with small impactors (including those that ultimately miss) may need to be made every few years, if we can predict them. Hyped or unreliable media stories might happen annually.
David Morrison also discussed some of these issues, looking at the historical progression of perspectives on the impact hazard.
1. Assessing the hazard. During the 1990s, the standard scientific tools of sampling and statistical analysis were essential to understand the impact hazard and communicate the risk to decision makers. Clark Chapman and David Morrison first identified the threshold for global damage and estimated the risk from impacts of different size. This early work compared the impact risk to other natural hazards, estimated the risk as a function of NEO size, and laid the foundation for establishing the Spaceguard Survey in 1998. The first Congressional language (in 1991) reflected this perspective when it noted, "the Committee believes it is only prudent to assess the nature of the threatŠ" Note that while these statistical studies provide a tool to analyze various mitigation schemes, they do not in themselves reduce the hazard. The step of moving from a scientific risk-analysis perspective to actually mitigating the impact hazard required a major re-orientation of thinking.
2. Mitigating the Hazard. The public and decision-makers are not interested in a better statistical understanding of the impact threat; they want warning and protection. The public-policy goal is not to refine the estimate of the risk but to identify the next impactor and do something about it. That is the purpose of surveys, orbital calculations, and follow-up characterization. The Spaceguard goal of finding 90% of the NEAs larger than 1 km diameter focuses on NEAs that are large enough to risk a global catastrophe. These are also the impacts that might threaten the survival of civilization. While such impacts are very rare, happening less than once in a million years, they still dominate the risk over more frequent impacts. Future surveys (such as Pan-STARRS and LSST) are also designed to provide decades of warning. The objective is not the last-minute detection of incoming objects, and the surveys have not been optimized for such purposes.
3. Dealing with Public Concerns. Issues that worry the public (and many decision makers) are not necessarily the greatest threats. The very rare large impacts pose the greatest hazards, but most people are more concerned about the next impact (which is likely to be small). 2008 TC3 is an example; too small to pose any danger, but something that would be of substantial public interest if it fell over a populated region. From this perspective, it is the number of "threat warnings" that matters, not the size of the threat. A 20 m object detected this week with one-week warning time will get much more attention than a 2 km object that won't actually threaten an impact for the next century. Ideally we should design a survey system that detects both distant large NEAs and close small ones. But (Morrison argued) if a choice must be made between optimizing for the deep surveys and searching for small impactors near the Earth, then it is more important to maintain the capability of detecting larger NEAs at great distances in deep surveys. The larger asteroids still dominate the hazard. Faced with both a cloud of mosquitoes and a venomous snake, we may be tempted just to go after the numerous mosquitoes, but we ignore the snake at our peril.
DESTRUCTIVE POTENTIAL OF IMPACTS BY SMALL NEAS
As the focus of new searches moves toward smaller (sub-km) NEAs, we are also learning more about the destructive potential of impacts at the smaller end of the NEA size spectrum. Mark Boslough (Sandia National Laboratories) and Galen Gisler (University of Oslo) both have used supercomputer models to investigate airbursts and tsunami formation, respectively.
Boslaugh has been simulating low-altitude airbursts of hypervelocity impacts from NEAs <100 m in diameter, finding an increased damage potential relative to earlier models that did not include the downward momentum of the exploding mass. Fireballs from nuclear explosions rise, but those from an asteroid initially continue downward from the point of disintegration. Because of this downward flow, larger blast waves and stronger thermal radiation pulses are experienced at the surface than would be produced for a nuclear airburst of the same yield. The 1908 Tunguska explosion is an example of an airburst in which the hot jet of vaporized projectile material continued downward but lost momentum before it made contact with the surface. The models suggest that the total energy released in the Tunguska event was not more than 5 megatons, in contrast to earlier analyses that suggested an energy of 10-15 megatons. For somewhat larger impacts, the fireball descends all the way to the ground, where it can melt silicate materials. The mysterious Libyan glass may have been produced by such a fireball.
Gisler (with co-author R. Weaver) did 2-D and 3-D computational analyses of the effects of ocean impacts of NEAs <500 m in diameter. They concluded that the near-field effects (that is, within 100 km of the impact) are the dominant danger, with central jets rising several km into the atmosphere and generating highly non-linear breaking waves that could devastate shorelines. However, the impact does not generate long-distance tsunami-like waves, so the area of damage remains local.
NEO POPULATION AND IMPACT RISK
With the nominal completion of the 10-year Spaceguard Survey focused on NEAs >1 km diameter, it is important to assess where we stand. Alan Harris (Space Science Institute) provided for this conference a re-evaluation of the population of NEAs and an estimate of the remaining risk from impacts. As of January 19, 2009, the present surveys have discovered 765 NEAs larger than 1 km (as estimated from their brightness) out of an estimated total population of 940. This is 81% completeness. Note that these numbers reflect a re-evaluation made a few years ago to the asteroid magnitude scale and the conversion factor from observed magnitudes to diameters, resulting in a fewer NEAs >1 km. Since the survey is more nearly complete at 2 km diameter, which is close to the probable threshold for globally catastrophic impacts, the Spaceguard Survey has actually "retired" more than 90% of the total impact risk. Almost half of all NEAs as large as Apophis have already been discovered, but only a negligible fraction of Tunguska-size NEAs.
As noted above, it now appears that ground damage from airbursts extends to considerably smaller impactor sizes than was previously inferred. The main risk in the size range from 150 m to 1000 m is from tsunamis, but with adequate warning the actual fatalities from tsunamis can be small. Harris re-evaluates the likely casualties using known population distributions and improved estimates of the damage from impacts. With the current level of survey completeness (which includes many sub-km objects as well as larger ones), Harris estimates that the remaining risk from the undiscovered population (expressed as average annual fatalities) is roughly 20/yr from local/regional land impacts, 4/yr from impact tsunamis, and 54/yr from globally catastrophic events (the undiscovered big ones). The next generation surveys, aimed at finding 90% of NEAs >140 m, will further reduce impact risk. Using these models of population, completion, and impact damage, Harris estimates a residual risk of roughly 6/yr from local/regional impacts, <1/yr from impact tsunamis, and 11/yr from globally catastrophic events, plus a continuing background risk of 10/yr from long-period comets.
Harris concluded that within a few years, if not already, we will have found essentially all dangerous asteroids large enough to be a risk of global climatic effects. We will be left with some fractional probability that even one such object remains undiscovered. Mid-size impacts, presenting mainly tsunami risk, are less frequent and probably less damaging than previously estimated. In the smallest size range capable of causing ground damage, the next generation survey may find ~25%, providing long-term warning. Ground-based optical surveys can also be designed with about 25-35% chance of detecting a "death plunge" object, down to the smallest size capable of producing ground damage, providing days to weeks' warning. Thus in a very short time on the scale of civilizations, and even quite short in terms of a human lifetime, the impact hazard should be reduced to a negligible risk. The one exception to this is the risk from long-period comets, for which present technology can offer no protection beyond short-term warning. Fortunately this risk is estimated to be quite small. Harris also noted that it is obvious that doing something about the global catastrophic events is worthwhile by almost any accounting. It is in the smaller size range where more careful cost-benefit accounting is in order to evaluate programs and policies.
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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.
27 May 2009
Foxnews Article: "Russian Scientist: UFO Crashed Into Meteorite to Save Earth"
"Russian Scientist: UFO Crashed Into Meteorite to Save Earth"
Wednesday, May 27, 2009
From the article...
Did a UFO deliberately crash into a meteor to save Earth 100 years ago? That's what one Russian scientist is claiming.
Dr. Yuri Labvin, president of the Tunguska Spatial Phenomenon Foundation, insists that an alien spacecraft sacrificed itself to prevent a gigantic meteor from slamming into the planet above Siberia on June 30, 1908.
The result was was the Tunguska event, a massive blast estimated at 15 megatons that downed 80 million trees over nearly 100 square miles. Eyewitnesses reported a bright light and a huge shock wave, but the area was so sparsely populated no one was killed.
Most scientists think the blast was caused by a meteorite exploding several miles above the surface. But Labvin thinks quartz slabs with strange markings found at the site are remnants of an alien control panel, which fell to the ground after the UFO slammed into the giant rock.
"We don't have any technologies that can print such kind of drawings on crystals," Labvin told the Macedonian International News Agency. "We also found ferrum silicate that can not be produced anywhere, except in space."
Link: Foxnews Article
Wednesday, May 27, 2009
From the article...
Did a UFO deliberately crash into a meteor to save Earth 100 years ago? That's what one Russian scientist is claiming.
Dr. Yuri Labvin, president of the Tunguska Spatial Phenomenon Foundation, insists that an alien spacecraft sacrificed itself to prevent a gigantic meteor from slamming into the planet above Siberia on June 30, 1908.
The result was was the Tunguska event, a massive blast estimated at 15 megatons that downed 80 million trees over nearly 100 square miles. Eyewitnesses reported a bright light and a huge shock wave, but the area was so sparsely populated no one was killed.
Most scientists think the blast was caused by a meteorite exploding several miles above the surface. But Labvin thinks quartz slabs with strange markings found at the site are remnants of an alien control panel, which fell to the ground after the UFO slammed into the giant rock.
"We don't have any technologies that can print such kind of drawings on crystals," Labvin told the Macedonian International News Agency. "We also found ferrum silicate that can not be produced anywhere, except in space."
Link: Foxnews Article
22 May 2009
Move An Asteroid 2009 International Technical Paper Competition is Go
The Move An Asteroid 2009 International Student and Young Professional Technical Paper Competition is once again being held. It is being administered by the Space Generation Advisory Council (SGAC).
Rules: 3-10 page technical paper on how to change the course of an asteroid. First price is a trip to South Korea in October to attend the Space Generation Congress (SGC) and International Astronautical Congress (IAC).
Link: SGAC Announcement: Space Generation Advisory Council announces “Move An Asteroid 2009” competition
Link: Move An Asteroid 2009 site
Rules: 3-10 page technical paper on how to change the course of an asteroid. First price is a trip to South Korea in October to attend the Space Generation Congress (SGC) and International Astronautical Congress (IAC).
Link: SGAC Announcement: Space Generation Advisory Council announces “Move An Asteroid 2009” competition
Link: Move An Asteroid 2009 site
20 May 2009
"Life Could Have Survived Earth's Early Bombardment"
The bombardment of Earth by asteroids 3.9 billion years ago may have enhanced early life, according to a new University of Colorado study. Credit: NASA/JPLSelections from the NASA Press Release...
A NASA-funded study indicates that an intense asteroid bombardment nearly 4 billion years ago may not have sterilized the early Earth as completely as previously thought. The asteroids, some the size of Kansas, possibly even provided a boost for early life.
The study focused on a particularly cataclysmic occurrence known as the Late Heavy Bombardment, or LHB. This event occurred approximately 3.9 billion years ago and lasted 20 to 200 million years. In a letter published in the May 21 issue of Nature magazine titled "Microbial Habitability of the Hadean Earth during the Late Heavy Bombardment," Oleg Abramov and Stephen J. Mojzsis, astrobiologists at the University of Colorado's Department of Geological Sciences, report on the results of a computer modeling project designed to study the heating of Earth by the bombardment.
Results from their project show that while the Late Heavy Bombardment might have generated enough heat to sterilize Earth's surface, microbial life in subsurface and underwater environments almost certainly would have survived.
"Exactly when life originated on Earth is a hotly debated topic," said Michael H. New, the astrobiology discipline scientist and manager of the Exobiology and Evolutionary Biology Program at NASA Headquarters in Washington. "These findings are significant because they indicate that if life had begun before the LHB or some time prior to 4 billion years ago, it could have survived in limited refuges and then expanded to fill our world."
"Even under the most extreme conditions we imposed on our model, the bombardment could not have sterilized Earth completely," said Abramov, lead author of the paper. "Our results are in line with the scientific consensus that hyperthermophilic, or 'heat-loving,' microbes could have been the earliest life forms on Earth, or survivors from an even more ancient biosphere. The results also support the potential for the persistence of microbial biospheres on other planetary bodies whose surfaces were reworked by the bombardment, including Mars."
NASA's Astrobiology Program's Exobiology and Evolutionary Biology Program and the NASA Astrobiology Institute at NASA's Ames Research Center at Moffett Field, Calif., through its support of NASA's Postdoctoral Program, provided funding for this research. The Astrobiology Program supports research into the origin, evolution, distribution and future of life on Earth and the potential for life elsewhere.
Selections from the news article...
Impact evidence from lunar samples, meteorites and the pockmarked surfaces of the inner planets paints a picture of a violent environment in the solar system during the Hadean Eon 4.5 to 3.8 billion years ago, particularly through a cataclysmic event known as the Late Heavy Bombardment about 3.9 million years ago.
No such record exists for Earth because tectonic processes have folded ancient craters back into the interior, but scientists assume our planet took the same pummeling.
Although many believe the bombardment would have sterilized Earth, the new study uses a computer model to show it would have melted only a fraction of Earth's crust, and that microbes — if any existed in the first 500 million years or so of Earth's existence — could well have survived in subsurface habitats, insulated from the destruction.
"These new results push back the possible beginnings of life on Earth to well before the bombardment period 3.9 billion years ago," said CU-Boulder Research Associate Oleg Abramov. "It opens up the possibility that life emerged as far back as 4.4 billion years ago, about the time the first oceans are thought to have formed."
Because physical evidence of Earth's early bombardment has been erased by weathering and plate tectonics over the eons, Abramov and his colleagues used data from Apollo moon rocks, impact records from the moon, Mars and Mercury, and previous theoretical studies to build three-dimensional computer models that replicate the bombardment.
The researchers plugged in asteroid size, frequency and distribution estimates into their simulations to chart the damage to the Earth during the Late Heavy Bombardment, which is thought to have lasted for 20 million to 200 million years.
The 3-D models allowed the researchers to monitor temperatures beneath individual craters to assess heating and cooling of the crust following large impacts in order to evaluate habitability, said Abramov. The study, detailed in the May 21 issue of the journal Nature, indicated that less than 25 percent of Earth's crust would have melted during such a bombardment.
The team even cranked up the intensity of the asteroid barrage in their simulations by 10-fold — an event that could have vaporized Earth's oceans.
"Even under the most extreme conditions we imposed, Earth would not have been completely sterilized by the bombardment," Abramov said.
Instead, hydrothermal vents may have provided sanctuaries for extreme, heat-loving microbes known as "hyperthermophilic bacteria" following bombardments, said study team member Stephen Mojzsis. Even if life had not emerged by 3.9 billion years ago, such underground havens could still have provided a "crucible" for life's origin on Earth, he added.
The modeling work was supported by the NASA Astrobiology Program's Exobiology and Evolutionary Biology Department and the NASA Postdoctoral Program.
The researchers concluded subterranean microbes living at temperatures ranging from 175 degrees to 230 degrees Fahrenheit (79 degrees to 110 degrees Celsius) would have flourished during the Late Heavy Bombardment. The models indicate that underground habitats for such microbes increased in volume and duration as a result of the massive impacts.
Some extreme microbial species on Earth today — including so-called "unboilable bugs" discovered in hydrothermal vents in Yellowstone National Park — thrive at 250 F (120 C).
Geologic evidence suggests that life on Earth was present at least 3.83 billion years ago, Mojzsis said.
Link: LiveScience Article
Link: NASA News Release
Link: 40th Lunar and Planetary Science Conference (2009) Abstract
Link: Article ("Earth science: Life battered but unbowed") in Nature 459, 335-336 (21 May 2009)
Link: Nature 459 Editor's Summary (21 May 2009)
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