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.

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

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

"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/JPL

Selections 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)

YouTube Video: Asteroid Impact Hazards with Dr. Alan Stern

Link: YouTube Video (Asteroid Impact Hazards with Dr. Alan Stern)

Video on Candian NEOSSAT Project

Video on Canadian NEEOSAT mission, a LEO microsatellite to track and determine orbits of near-Earth asteroids and comets, focusing on those in near-Sun orbits.

Link: Yahoo Video

Link: Project Homepage

Video: Kansas Man Digs Up 1,220-Pound Meteorite Estimated to be 20,000 Years Old

A Kansas man digs up a an meteorite estimated to be 20,000 years old. KWCH's Alana Rocha reports. Source: KWCH | Added May 11, 2009

From the news article...

Sunday just east of Greensburg, he [Don Stimpson, curator of the Kansas Meteorite Museum in Haviland] was ready to unearth his latest find - a rather odd-shaped piece Stimpson believes is a major chunk of the Brenham Meteorites.

It's estimated the meteorite has sat in the ground 20,000 years. And this day is the result of about two weeks of digging and a couple of months waiting on good Kansas weather to lift it out.

"Looks like 1,220 pounds," Stimpson calculates.

Link: CNN/KWCH Video

"Man Unearths Meteorite in SW Kansas"
10 May 2009 06:19 PM

Link: KWCH Story

Texas A&M University Class Work on Apophis Exploration and Mitigation Mission Design

Selections from the Texas A&M news release (as well as presentations on the class projects for Fall 2008 and Spring 2009)...

Dr. David Hyland of Texas A&M University began work on an exploration mission to the asteroid Apophis in 2006. The students in three courses offered by Hyland designed APEP, the Apophis Preliminary Exploratory Platform. This mission was meant to just explore Apophis and track its movements. The end result would be a decision on whether or not the asteroid had a high chance of colliding with Earth.

In fall of 2008, the Deflect Apophis System (DAS) was designed by students in another class led by Hyland, AERO 426. The objective of the DAS was to move Apophis such that it would not collide with Earth.

The Apophis Exploration and Mitigation Platform (AEMP) is the current project, which involves a combination of both APEP and AEMP. First, the AEMP would stand some distance away from Apophis, taking of all of the necessary science measurements needed to deflect the asteroid. Then, it would employ a “gravity tractor” to begin movement. After a year, an “albedo change” substance would be adhered to the asteroid, forcing long term movement.

Pending ongoing discussions, AEMP may soon be a three-way partnership involving Texas A&M, NASA Ames and the Kingdom of Saudi Arabia, through King Abdulaziz City for Science and Technology.

The concept of changing the albedo of an asteroid is a technique that is unique to Texas A&M. No other organization has designed a mission meant to use the manipulation of albedo as a way to move an asteroid. The albedo of an object is a measure of how reflective it is. The more reflective, the less heat it absorbs, and the less heat it emits as it cools. When the heat is emitted, a small force is created on the object. If the asteroid’s albedo is changed, this force can be manipulated to move Apophis over a long period of time.

Link: Texas A&M News Release

Link: DAS Class Project Overview (PDF)

Link: DAS Class Project Overview (PPT)

Link: Texas A&M Overview presentation (03 December 2008)

Link: Texas A&M Apophis Mitigation Research Project Kickoff Presentation (09 February 2009)

Asteroid Impact Simulator

Interesting multi-lingual asteroid impact simulator where you choose diameter, velocity, angle, composition, locations and a visual map with data boxes appears with impact values.

Link: Asteroid Impact Simulator

CSM Columnist: "Who is responsible for averting an asteroid strike?"

"Who is responsible for averting an asteroid strike?"
Column: It's time to set aside political quibbles and form an international plan

Asteroid hunters have good news – and a challenge – for the rest of us.After an extensive search for asteroids a kilometer or more across, engineer Steve Chesley says that “we can now say with confidence that no asteroids large enough to cause such a global calamity [as killing off the dinosaurs] are headed our way.”

But if one of them – or even a smaller, city-destroying rock – were detected on a collision course, would the world community be prepared to handle it? A conference of legal experts that discussed this question at the University of Nebraska in Lincoln last month answered it with a resounding “No.”

Scientists and engineers who have studied the problem of deflecting a dangerous asteroid believe the technical issues are difficult but solvable. The challenge now is figuring out the legal issues of who takes action on behalf of humankind and of what their responsibilities and liabilities will be.

Asteroid hunters believe they can give us plenty of warning. There is “a fair chance that the next Earth impactor will actually be identified with many decades and perhaps centuries of warning time,” explains Mr. Chesley of the NASA Jet Propulsion Laboratory in Pasadena, Calif., in the March/April issue of the Planetary Report.

That’s plenty of time to develop a spacecraft whose gravitational attraction might nudge an asteroid aside – or a rocket or some application of nuclear explosives to do the job.

However, if a single country – or small group of nations – tries to take the initiative on its own, the international reaction could stall any action at all.

“The international political reactions to the US shooting down one of its own satellites a year ago to prevent presumably dangerous and toxic rocket fuel from reaching Earth only foreshadows what would happen if the US would detonate nukes claiming to destroy an incoming asteroid,” said Frans von der Dunk, a University of Nebraska space law expert, at the Nebraska conference, according to Space News.

Overlooking the hype about nuclear weapons, which engineers consider an unlikely, extreme measure, Professor von der Dunk has pointed out the main issue. Averting a regional or global asteroid threat may involve unforeseen collateral damage – such as splintered chunks making their way to Earth or worse. Therefore, the world community has to have a say in how that threat is handled.
Right now, to use von der Dunk’s word, that community is “underorganized” to meet this challenge.

Getting organized for possible future action is less urgent than coping with global warming. But like any good insurance planning, it should not languish on the back burner of global politics.

This need will come into sharper focus as the new Pan-STARRS 1 telescope in Hawaii goes into action this spring. Its mission to catalogue objects across the entire sky will pick out many more asteroids, large and small.

Someday those facts may foretell a future impact. The world community should make sure that it has its response plan in order with the legal mechanism for assigning responsibilities in place.

Robert C. Cowen
14 May 2009
Link: Christian Science Monitor Column