This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

30 June 2008

Move An Asteroid 2008 Technical Paper Winners Annouced

From a competition I helped organize with the Space Generation Advisory Council (SGAC). I must thank the judges at SpaceWorks, my home organization, for assisting me in reviewing all the entrants. We hope to continue this competition next year.

Space Generation Advisory Council Announces Winners of “Move An Asteroid 2008” International Competition on 100th Anniversary of Tunguska Explosion

The Space Generation Advisory Council, the world’s largest group representing youth perspectives on space exploration to the United Nations and national space programs today announced the winners of an international youth technical paper competition to develop unique and innovative concepts for how to deflect an asteroid or comet that could impact the Earth (referred to as mitigation). The SGAC announced the competition results on the 100th anniversary of the last major impact of the Earth by an asteroid or comet, known as the Tunguska explosion. Financial support for this competition is provided by Northrop Grumman Corporation, Lockheed Martin Corporation, SpaceWorks Commercial, and The Planetary Society.

First place in the competition is awarded to Mary D'Souza of the Department of Mechanical Engineering at the University of Queensland in Australia for her paper entitled “A Body Solar Sail Concept for the Deflection of 99942 Apophis.” Ms. D'Souza’s concept involves wrapping an asteroid in a reflective film (referred to as a “body” solar sail). Such a coating may increase the asteroid’s reflectivity, enabling deflection by solar radiation pressure. Ms. D'Souza will receive a trip to present her paper at this year's Space Generation Congress (SGC) and International Astronautical Congress (IAC) which take place in Glasgow, Scotland from late September until early October 2008.

Second place is awarded to Mr. Andrew Bacon of the Department of Electronic and Electrical Engineering at the University of Bath in Bath, United Kingdom for his paper entitled “The Use of Electromechanical Resonators for the Mitigation of Earth Threatening Asteroids and Comets.” Mr. Bacon’s concept involves the use of electromechanical resonators to build up waves within an asteroid or comet that would break it up. Mr. Bacon will receive a trip to present his paper at this year’s SGC.

"We received submissions from all over the world and thank all the participants for developing creative Near Earth Object (NEO) mitigation strategies. The first and second place winners demonstrated an ability to think creatively about the problem and to explain it to the judges.”, said A.C. Charania, administrator of the Move An Asteroid 2008 Competition. "We hope to continue this competition next year and look forward to the presentations of the winners at this year’s Space Generation Congress (SGC) and International Astronautical Congress (IAC)."

"It is great to see such an interest in this topic from young people all over the world. Hopefully with competitions like this, SGAC can further increase the involvement of youth in this important field of current space research.", said Alex Karl, Co-Chairperson of the Space Generation Advisory Council.

Link: Move An Asteroid 2008 Website

Link: SGAC Press Release PDF

Link: Press Release

YouTube Video: "Scientists baffled by flattened forest -- 100 years on"

A century ago 2,000 square kilometres of Siberian forest were flattened in an apparent explosion. The event has puzzled scientists ever since and, although theories abound as to the cause of the blast, nobody has managed to find out exactly why 80 million trees toppled over near the Tunguska River in 1908.

Link: YouTube Video (Scientists baffled by flattened forest -- 100 years on)

YouTube Video: "A visit to the site of the Tunguska explosion"

New Scientist features editor David Cohen narrates his journey to the site of the Tunguska explosion in Siberia.

Link: YouTube Video (A visit to the site of the Tunguska explosion)

The Planetary Society's Press Release on Tunguska Anniversary

From the press release...

Date Released: Saturday, June 28, 2008
Source: Planetary Society - Comments Comments

Target Earth: How Prepared Are We for Another Tunguska?

100th Anniversary of Vast Explosion in Siberia


US Congressman Dana Rohrabacher, 46th District of California
Louis Friedman, Executive Director, The Planetary Society
Bruce Betts, Director of Projects, The Planetary Society
Alan W. Harris, Senior Research Scientist, Space Science Institute
Don Yeomans, Manager of NASA's Near-Earth Object Program Office, Jet Propulsion Laboratory

Date: Monday, June 30, 2008
Time: 11:00 AM
Place: The Planetary Society, 65 N Catalina Avenue, Pasadena, CA

A fireball from the sky exploded over the forest near Siberia's Podkamennaya Tunguska River 100 years ago today. The blast leveled 2000 square kilometers of trees, flattening them like matchsticks. Imagine what would happen if a similar object from space - probably an asteroid - exploded over one of Earth's cities today.

Join us at a press conference hosted by The Planetary Society that will feature representatives from the government, science and space advocacy outlining the threat that near-Earth objects pose to the world today and what we can do to make our planet safer.

* See images of a vast Siberian forest leveled.

* Discover what a similar explosion would do to a city like Los Angeles or New York today.

* Learn what's happening in Congress regarding saving the world's largest radiotelescope, Arecibo, to help track near-Earth objects.

* Hear what steps we are taking, and still need to take, to make our world safer from impact threats.

Participants will be available for questions during the press conference and private interviews following it. Please RSVP or call Susan Lendroth for more details, 626-793-5100 ext 237 or

Link: SpaceRef Press Release

On this 1908...Tunguska (roundup of several articles)

On this, the 100th anniversary of the Tunguska explosion, here is roundup of articles.

"Fire in the sky: Tunguska at 100"
Paul Rincon
BBC News
Link: BBC Article

"Huge Tunguska Explosion Remains Mysterious 100 Years Later"
Link: article

"Tunguska: The day the sky exploded"
Link: NewScientist article

"Asteroid anniversary recalls Earth's rocky history"
Link: USAToday article

"June 30, 1908: A Very Close Encounter of the Second Kind"
Link: article

"Apocalypse Then. Next One, When?"
Andrew C. Revkin
30 June 2008
Link: New York Times article

"The Tunguska Event: A Century Later, It’s Still Mysterious"
Link: Discover Magazine article

"Target Earth: Hie Prepared Are We"
Planetary Society Press Release
26 June 2008
Link: Planetary Society Press Release

"Tunguska: 100 Years and Counting"
J. Kelly Beatty
30 June 2008
Link: Sky and Telescope Article

"The Tunguska Event--100 Years Later"
30 June 2008
Link: NASA News Article
Link: NASA Article Podcast (.mp3)

"A Century of Tunguska"
30 June 2008
Link: Archy Article on Tunguska

"Impact Earth: Avoiding another asteroid"
02 July 2008
Link: The Independent Article

29 June 2008

Article: German Smallsat NEO Detection Mission (similar to Canadian NEOSSat)

Similar to the Canadian NEOSSat mission, from the article...

German scientists said Thursday they are planning a satellite especially to hunt space rocks that might slam into the planet Earth and wipe out complete cities or countries. The modest satellite, costing 15 million euros (24 million dollars), would scan space for near earth objects. An NEO is a celestial body which orbits the Sun on a track that crosses Earth's orbit.

The German space agency DLR said modelling showed there must be more than 1,000 such objects more than 100 metres wide, but only nine have been discovered so far.

It spoke as the centenary approaches of the June 30, 1908 Tunguska Event.

The DLR said its interpretation of that event was that a rock 30 to 50 metres wide entered the atmosphere over Siberia and exploded 8 to 12 kilometres above the surface, destroying 2,000 square kilometres of forest.

"It's vital to identify NEOs before they get onto a collision course with the Earth," said Ekkehard Kührt of the DLR planetary research institute.

Development work on the satellite is probably to begin this autumn. The satellite would also track space junk, which consists of satellite debris orbiting the Earth.

DLR says that with sufficient warning time, such as 10 years, an NEO could be nudged away into an orbit that did not threaten the Earth. A spacecraft could crash into the NEO and knock off a chunk, leading to a change in the NEO's track.

Earth Times
26 June 2008

Link: Earth Times Article

Russians Contend that Phobos Grunt Mission Can Be Altered into Apophis Radio Beacon Mission

Selections from the article...

Russian scientists think a space probe should plant a radio beacon on the asteroid Apophis to determine whether it's going to impact Earth, a conference report said Friday.

The report also conjectured that the Russian Phobos-Grunt spacecraft presently scheduled to be launched in 2009 could accomplish that mission with only slight payload changes, but that its launch would have to be delayed until 2012 to make a rendezvous with Apophis.

Such an Apophis impact "could lead to an area equal to France turning into a desert," said Alexander Simonov, one of the authors of the Russian report, in an understatement of the level of global destruction that would be unleashed by a meteor strike of that magnitude.

The report said that even the largest of ground-based radio telescopes cannot discern the orbit of Apophis with the required precision, so one potential solution would be to plant a radio beacon on the asteroid that could permit radio astronomers to determine its orbit within an accuracy of "tens of meters. " That would reveal whether Apophis will hit Earth.

"We propose the Phobos-Grunt spacecraft... as a platform for this mission," the report said. Phobos-Grunt is a planned Russian sample return mission to the Martian moon Phobos. Designed starting in 2001, Phobos-Grunt is currently scheduled for launch in 2009. If the spacecraft's mission is amended to rendezvous with Apophis, the report said its launch should be delayed to May 13, 2012, and the flight is expected to take 330 days.

"Russians offer to track asteroid threat"
Egan Orion
London Inquirer
28 June 2008

Link: London Inquirer Article

Air & Space/Smithsonian Magazine Article on Human NEO Missions

"The Million Mile Mission: A small band of believers urges NASA to take its next step—onto an asteroid."
Michael Klesius
Air & Space Magazine
01 July 2008

Link: Air & Space/Smithsonian Magazine Article

AFP Tunguska Article

From the article...

A hundred years ago this week, a gigantic explosion ripped open the dawn sky above the swampy taiga forest of western Siberia, leaving a scientific riddle that endures to this day.

A dazzling light pierced the heavens, preceding a shock wave with the power of a thousand atomic bombs which flattened 80 million trees in a swathe of more than 2,000 square kilometres (800 square miles).

Evenki nomads recounted how the blast tossed homes and animals into the air. In Irkutsk, 1,500 kilometres (950 miles) away, seismic sensors registered what was initially deemed to be an earthquake. The fireball was so great that a day later, Londoners could read their newspapers under the night sky.

What caused the so-called Tunguska Event, named after the Podkamennaya Tunguska river near where it happened, has spawned at least a half a dozen theories.

The biggest finger of blame points at a rogue rock whose destiny, after travelling in space for millions of years, was to intersect with Earth at exactly 7:17 am on June 30, 1908.

Even the most ardent defenders of the sudden impact theory acknowledge there are many gaps. They strive to find answers, believing this will strengthen defences against future Tunguska-type threats, which experts say occur with an average frequency from one in 200 years to one in 1,000 years.

"Imagine an unspotted asteroid laying waste to a significant chunk of land... and imagine if that area, unlike Tunguska and a surprising amount of the globe today, were populated," the British science journal Nature commented last week.

If a rock was the culprit, the choices lie between an asteroid -- the rubble that can be jostled out of its orbital belt between Mars and Jupiter and set on collision course with Earth -- and a comet, one of the "icy dirtballs" of frozen, primeval material that loop around the Solar System.

-- 'Why has no one yet found fragments?' --


Comets move at far greater speeds than asteroids, which means they release more kinetic energy pound-for-pound upon impact. A small comet would deliver the same punch as a larger asteroid.

But no fragments of the Tunguska villain have ever been found, despite many searches.

Finding a piece is important, for it will boost our knowledge about the degrees of risk from dangerous Near Earth Objects (NEOs), say Italian researchers Luca Gasperini, Enrico Bonatti and Giuseppe Longo.

When a new asteroid is detected, its orbit can be plotted for scores of years in the future.

Comets are far less numerous than asteroids but are rather more worrying, as they are largely an unknown entity.

Most comets have yet to be spotted because they take decades or even hundreds of years to go around the Sun and pass our home. As a result, any comet on a collision course with Earth could quite literally come out of the dark, leaving us negligible time to respond.

"(I)f the Tunguska event was in fact caused by a comet, it would be a unique occurrence rather than an important case study of a known class of phenomena," Gasperini's team write in this month's issue of Scientific American.

"On the other hand, if an asteroid did explode in the Siberian skies that June morning, why has no-one yet found fragments?"

NEO experts are likewise unsure about the size of the object.

Estimates, based on the scale of ground destruction, range from three metres (10 feet) to 70 metres (227 feet).

All agree that the object, heated by friction with atmospheric molecules, exploded far above ground -- between several kilometres (miles) and 10 kms (six miles).

But there is fierce debate as to whether any debris hit the ground.

This too is important. When the next Tunguska NEO looms, Earth's guardians will have to choose whether to try to deflect it or blow it up in space, with the risk that objects of a certain size may survive the fiery passage through the atmosphere and hit the planet.

The Italian trio believe the answers lie in a curiously-shaped oval lake, called Lake Cheko, located about 10 kilometres (six miles) from ground zero.

Computer models, they say, suggest it is the impact crater from a metre- (three-feet) -sized fragment that survived the explosion.

They plan a return expedition to Lake Cheko in the hope of reaching a dense object of this size, buried 10 metres (32.5 feet) in the lake's cone-shaped floor, that reflected sonar waves.

But what if neither comet nor asteroid were to blame?

A rival theory is given an airing in this week's New Scientist.

Lake Cheko does not have the typical round shape of an impact crater, and no extraterrestrial material has been found, which means "there's got to be a terrestrial explanation," Wolfgang Kundt, a physicist at Germany's Bonn University told the British weekly.

He believes the Tunguska Event was caused by a massive escape of 10 million tonnes of methane-rich gas deep within Earth's crust. Evidence of a similar apocalyptic release can be found on the Blake Ridge on the seabed off Norway, a "pockmark" of 700 sq. kms (280 sq. miles), Kundt said.

"100 years on, mystery shrouds massive 'cosmic impact' in Russia"
29 June 2008

Link: AFP Article

Tunguska Article from NASA/JPL

From the article...

100 Years of Space Rock: The Tunguska Impact
June 27, 2008

At around 7:17 on the morning of June 30, 1908, a man based at the trading post at Vanavara in Siberia is sitting on his front porch. In a moment, 40 miles from the center of an immense blast of unknown origin, he will be hurled from his chair and the heat will be so intense he will feel as though his shirt is on fire. The man at the trading post, and others in a largely uninhabited region of Siberia, near the Podkamennaya Tunguska River, are to be accidental eyewitnesses to cosmological history.

"If you want to start a conversation with anyone in the asteroid business all you have to say is Tunguska," said Don Yeomans, manager of the Near-Earth Object Office at NASA's Jet Propulsion Laboratory. "It is the only entry of a large meteoroid we have in the modern era with first-hand accounts."

While the impact occurred in '08, the first scientific expedition to the area would have to wait for 19 years. In 1921, Leonid Kulik, the chief curator for the meteorite collection of the St. Petersburg museum led an expedition to Tunguska. But the harsh conditions of the Siberian outback thwarted his team's attempt to reach the area of the blast. In 1927, a new expedition, again lead by Kulik, reached its goal.

"At first, the locals were reluctant to tell Kulik about the event," said Yeomans. "They believed the blast was a visitation by the god Ogdy, who had cursed the area by smashing trees and killing animals."

While testimonials may have at first been difficult to obtain, there was plenty of evidence lying around. Eight hundred square miles of remote forest had been ripped asunder. Eighty million trees were on their sides, lying in a radial pattern.

"Those trees acted as markers, pointing directly away from the blast's epicenter," said Yeomans. "Later, when the team arrived at ground zero, they found the trees there standing upright -- but their limbs and bark had been stripped away. They looked like a forest of telephone poles."

Such debranching requires fast moving shock waves that break off a tree's branches before the branches can transfer the impact momentum to the tree's stem. Thirty seven years after the Tunguska blast, branchless trees would be found at the site of another massive explosion -- Hiroshima, Japan.

Kulik's expeditions (he traveled to Tunguska on three separate occasions) did finally get some of the locals to talk. One was the man based at the Vanara trading post who witnessed the heat blast as he was launched a few yards. His account:

Suddenly in the north sky… the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire… At that moment there was a bang in the sky and a mighty crash… The crash was followed by a noise like stones falling from the sky, or of guns firing. The earth trembled.

The massive explosion packed a wallop. The resulting seismic shockwave registered with sensitive barometers as far away as England. Dense clouds formed over the region at high altitudes which reflected sunlight from beyond the horizon. Night skies glowed, and reports came in that people who lived as far away as Asia could read newspapers outdoors as late as midnight. Locally, hundreds of reindeer, the livelihood of local herders, were killed, but there was no direct evidence that any person perished in the blast.

"A century later some still debate the cause and come up with different scenarios that could have caused the explosion," said Yeomans. "But the generally agreed upon theory is that on the morning of June 30, 1908, a large space rock, about 120 feet across, entered the atmosphere of Siberia and then detonated in the sky."

It is estimated the asteroid entered Earth's atmosphere traveling at a speed of about 33,500 miles per hour. During its quick plunge, the 220-million-pound space rock heated the air surrounding it to 44,500 degrees Fahrenheit. At 7:17 a.m. (local Siberia time), at a height of about 28,000 feet, the combination of pressure and heat caused the asteroid to fragment and annihilate itself, producing a fireball and releasing energy equivalent to about 185 Hiroshima bombs.

"That is why there is no impact crater," said Yeomans. "The great majority of the asteroid is consumed in the explosion."

Yeomans and his colleagues at JPL's Near-Earth Object Office are tasked with plotting the orbits of present-day comets and asteroids that cross Earth's path, and could be potentially hazardous to our planet.

Yeomans estimates that, on average, a Tunguska-sized asteroid will enter Earth's atmosphere once every 300 years. On this 100th anniversary of the Tunguska event, does that mean we have 200 years of largely meteor-free skies?

"Not necessarily," said Yeomans. "The 300 years between Tunguska-sized events is an average based on our best science. I think about Tunguska all the time from a scientific point of view, but the thought of a another Tunguska does not keep me up at night."

100 Years of Space Rock: The Tunguska Impact
NASA/JPL News Article
June 27, 2008

Link: NASA/JPL Article

26 June 2008

Book: "T. rex" and the Crater of Doom - New Edition Out

A new edition of the 1997 book by geologist Walter Alvarez entitled "T. Rex and the Crater of Doom" has been published. It has been reprinted in June 2008 by Princeton University Press.


One of the great mysteries is what happened to the dinosaurs, and it has taken great detective work to give us an answer. In T. Rex and the Crater of Doom, some brilliant, not to mention determined, scientists roam the world and seek out the clues. What they conclude is that the earth withstood a colossal impact with a meteor (or perhaps a comet) 65 million years ago. The resulting cataclysm destroyed half the life on the planet.

Walter Alvarez, a geologist at the University of California at Berkeley, and one of the four scientists who present this theory on the mystery, tells the story in a clear narrative that contains a wealth of scientific material. The book does require an investment of attention, but the presentation is quite readable, and the story itself is fascinating.

Link: Introduction to Book (at The Loom)

Link: Entire Introduction the Book


Chesapeake Bay Impact Analysis

From the far reaches of the solar system, a giant asteroid or comet plunged into Earth near what is now the Chesapeake Bay 35 million years ago (shown in this artist's conception). Credit: © The Virginian-Pilot.

From the article...

The true impact of an asteroid or comet crashing near the Chesapeake Bay 35 million years ago has been examined in detail for the first time. The analysis reveals the resilience of life in the aftermath of disaster.

The impact crater, which is buried under 400 to 1,200 feet (120 to 365 meters) of sand, silt and clay, spans twice the length of Manhattan. The sprawling depression helped create what would eventually become Chesapeake Bay. About 10,000 years ago, ice sheets began to melt and once-dry river valleys filled with water. The rivers of the Chesapeake region converged directly over the buried crater, according to the U.S. Geological Survey (USGS).

Gregory Gohn of the USGS and his colleagues analyzed samples from two deep holes drilled into the crater near its center.

"I think what we wanted to do is drill into the central part of the crater and get as long of a section as we could and understand the processes that put them in the order we found them," Gohn told

Within seconds of the object's touchdown, rocks were flung high into the air. The force of the impact carved a colossal cavity and caused temperatures to skyrocket, turning brittle rocks into taffy. Then, material along the cavity's rim surged downhill into the bowl-shaped depression like an avalanche.

The extreme heat, the researchers say, killed off most life. However, they found abundant microbes living today in the deepest parts of the crater. Some of the ancient bacteria would have survived the impact, the researchers say, because their little hideouts didn't feel the brunt of the heat. The rest of the abundant and newly discovered microbial life is thought to have recolonized the zapped area possibly tens of thousands of years following the impact when temperatures dropped to habitable levels.

"The impact broke up and disaggregated all of these blocks of rock," said researcher Mary Voytek, a microbiologist at the USGS, "and that actually creates space for [the microbes] to colonize and it also creates new routes for water and material to move though, which is always good for bugs."

So a catastrophic event like this could actually be a boon to microbes, at least in the long-run, Voytek said. The impact breaks up compacted rock to create nooks and crannies for bacteria to reside in, and it also brings in a fresh supply of food.

"It's somewhat analogous to whale falls," when a whale carcass eventually settles on the sea floor, Voytek said. "All of a sudden it's a restaurant for these bugs."

Understanding the biological effects of this asteroid impact will shed light on the potential for life deep underground during Earth's Archaean period, 3.8 billion to 2.5 billion years ago, when impacts were more frequent than today. The results also have implications for predicting life in the deep biosphere on Mars.

"If we're going to find life [on Mars], everyone agrees a good place to look is in the subsurface," Voytek said.

The project, which is detailed in the June 27 issue of the journal Science, was funded by the USGS, NASA, the National Science Foundation, the Austrian Science Foundation and DOSECC Inc.

"Life Survived Catastrophic Space Rock Impact"
Jeanna Bryner
26 June 2008

Link: article



Science 27 June 2008:
Vol. 320. no. 5884, pp. 1740 - 1745
DOI: 10.1126/science.1158708

Deep Drilling into the Chesapeake Bay Impact Structure
G. S. Gohn,1* C. Koeberl,2 K. G. Miller,3 W. U. Reimold,4 J. V. Browning,3 C. S. Cockell,5 J. W. Horton, Jr.,1 T. Kenkmann,4 A. A. Kulpecz,3 D. S. Powars,1 W. E. Sanford,1 M. A. Voytek1

Samples from a 1.76-kilometer-deep corehole drilled near the center of the late Eocene Chesapeake Bay impact structure (Virginia, USA) reveal its geologic, hydrologic, and biologic history. We conducted stratigraphic and petrologic analyses of the cores to elucidate the timing and results of impact-melt creation and distribution, transient-cavity collapse, and ocean-water resurge. Comparison of post-impact sedimentary sequences inside and outside the structure indicates that compaction of the crater fill influenced long-term sedimentation patterns in the mid-Atlantic region. Salty connate water of the target remains in the crater fill today, where it poses a potential threat to the regional groundwater resource. Observed depth variations in microbial abundance indicate a complex history of impact-related thermal sterilization and habitat modification, and subsequent post-impact repopulation.

1 U.S. Geological Survey, Reston, VA 20192, USA.
2 Department of Lithospheric Research, Center for Earth Sciences, University of Vienna, Althanstrasse 14, Vienna A-1090, Austria.
3 Department of Geological Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ08854, USA.
4 Museum of Natural History (Mineralogy), Humboldt-University Berlin, Invalidenstrasse 43, Berlin 10115, Germany.
5 Centre for Earth, Planetary, Space, and Astronomical Research, Open University, Milton Keynes MK7 6AA, UK.

Link: Science Abstract

Additional Articles on Canadian NEO Search Small Satellite: NEOSSat

Additional articles on Canadian NEO search satellite, NEOSSat. From the articles...

On Thursday, the Canadian Space Agency and Defence Research Development Canada announced they are preparing to launch the Near Earth Object Surveillance Satellite, or NEOSSat, a suitcase-sized telescope capable of spotting asteroids and tracking high-altitude satellites and space debris.

NEOSSat follows on the success of the MOST (Microvariability and Oscillations of STars) telescope, the 60 kg star-watching satellite that was launched in 2003 and operates on a shoestring budget.

Like its predecessor, NEOSSat is tiny, with a mass of 65 kilograms and a telescope with a 15 centimetre aperture, smaller than most amateur astronomers' telescopes.

And like MOST, it will be cheap too, costing $12 million to build, launch and operate.

Scheduled to launch into space in 2010, NEOSSat will have two main science tasks: the NESS (Near Earth Space Surveillance) asteroid search program and the HEOSS (High Earth Orbit Space Surveillance) program, which will track satellites and other objects floating in high orbit around Earth.

The satellite, funded by the Canadian Space Agency and Defence Research & Development Canada and built by Mississauga-based Dynacon Inc., will also to keep an eye on satellites and floating debris orbiting the Earth.

Although NEOSSat's 15-centimetre telescope is smaller than most amateur astronomers', its location approximately 700 kilometres above Earth's atmosphere will give it a huge advantage in searching the blackness of space for faint signs of moving asteroids. Twisting and turning hundreds of times each day, orbiting from pole to pole every 50 minutes, and generating power from the Sun, NEOSSat will send dozens of images to the ground each time it passes over Canada. Due to the ultra-low sky background provided by the vacuum of space, NEOSSat will be able to detect asteroids delivering as few as 50 photons of light in a 100-second exposure.

Link: CBC News Article

Link: ScienceDaily Article

Link: NEOSSAT Home page

Russia's Academy of Sciences hosts forum on Tunguska phenomenon

Upcoming conference in Russia on the occasion of the 100th anniversary of the Tunguska explosion, selections from the article...

Russia's Academy of Sciences is hosting an international conference marking the 100th anniversary of the mysterious event which occurred on June 30, 1908 near the river Podkamennaya Tunguska, and has defied explanation up to date.

Boris Shustov, director of RAN's Institute of Astronomy and head of the expert group on asteroid-comet danger (ACO) under the Council for Outer Space, told Itar-Tass that "they often use the word "meteorite" when talking about this event; but it is the wrong term."

"In the course of the conference, the participants will discuss the Tunguska phenomenon proper and the asteroid-comet danger. They are our colleagues from the United States, Great Britain, and Germany, and we’re expecting extensive discussions of this theme. It has been proposed to bring forward a package of documents for consideration by the UN in 2009 which would regulate countries' conduct in connection with the asteroid-comet danger. ACO is a global threat," Shustov underlined.

Director of the center for planetary defense of the Earth from asteroids Anatoly Zaitsev said two lessons have to be learnt form the Tunguska Phenomenon.

"Firstly, it showed the Earth's vulnerability in the event of "asteroid attack." Secondly, it was a sort of warning: nations should consolidate their efforts as fast as possible in the cause to protect the planet from asteroids.

The international conference will last until June 28. Among its organizers are the Russian Academy of Sciences (RAN), the Moscow State University (MGU), the RAN committee on meteorites, and the MGU's Sternberg state astronomical institute.

Link: ITAR-TASS Story: "RAN hosts forum on Tunguska phenomenon" (26 June 2008)

Link: International Conference "100 years since Tunguska phenomenon: Past, present and future" - Conference Website

Link: International Conference "100 years since Tunguska phenomenon: Past, present and future" - Conference Abstracts (PDF)

25 June 2008

Dave Morrison: NEO News (06/25/08) Burger Bar that Saved the World

Dave Morrison's NEO News comments on the recent series of Articles in Nature (including one article in particular). Here is the NEO News (06/25/08) Burger Bar that Saved the World issue...

NEO News (06/25/08) Burger Bar that Saved the World

Nature is publishing a special edition this week on the 100th anniversary of the Tunguska impact. The first part to be released is this historical summary assembled by David Chandler from a series of separate interviews. The text is below, but I especially call your attention to the enclosed pdf file with the illustrations. The introductory "burger bar" cartoon is really funny (something we don't often say about NEOs).

Most of the history recounted here strikes me as accurate, except perhaps the statements that Gene Shoemaker resisted the idea that there was an impact hazard up until the discovery of Comet Shoemaker-Levy 9. My own experience over the preceding decade was that Gene understood the issues as well as any of us and fully supported the recommendations of the Spaceguard Survey workshop, a report to which Gene made important contributions. The split in the early 1990s was between the nuclear weapons labs and the astronomers, not among us astronomers. I credit Pete Worden's organization of the Erice NEO workshop, and Tom Gehrels for the Tucson Hazards meeting (both held in early 1993), for closing much of that rift between these two scientific communities.

David Morrison

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 For additional information, please see the website If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.

Nature Magazine has Special on Cosmic Impacts: Various Articles

Nature Magazine has several articles in a special section on impacts. Articles include the following:

All craters great and small (picture gallery)
From a 5-millimetre dent on a satellite to a 3-kilometre pit in the surface of Mars, the scars of impact events can be seen at every scale. We present a gallery of some particularly appealing ones from Earth and beyond.

Tunguska at 100
The most dramatic cosmic impact in recent history has gathered up almost as many weird explanations as it knocked down trees, writes Duncan Steel.
25 June 2008

The hole at the bottom of the Moon
A giant crater on the lunar farside holds the key to a catastrophic bombardment that reshaped the Moon, Earth and other planets. Eric Hand reports.
25 June 2008

The burger bar that saved the world
Fewer people are searching for near-Earth asteroids, astronomer David Morrison said in the 1990s, than work a shift in a small McDonalds. But that group — a little larger now — has over the past two decades discovered a host of happily harmless rocks, and in doing so reduced the risk of an unknown asteroid blighting civilization. David Chandler puts together the story in the words of those who watched, and those who watched the watchers.
25 June 2008

COMMENTARY: What Spaceguard did
A survey of large objects near Earth has shown that there is little risk of a cataclysmic impact in the next century. Alan Harris asks if such cataloguing efforts should continue.
25 June 2008

In retrospect: Lucifer's Hammer
Oliver Morton recalls how the first major science fiction novel to depict an impact event conjured the thrill and the horror of natural cataclysm — and even inspired some researchers.
25 June 2008

Message from the heavens
Discerning the meaning behind Maurizio Cattelan's violent, provocative and now highly valuable sculpture of Pope John Paul II felled by a meteorite raises many questions for viewers, explains Martin Kemp.
25 June 2008

Forming the martian great divide
Early in its history, Mars suffered a convulsion that left a lasting geological and topographical scar. The latest work adds to evidence that the cause was external — a massive impact.
25 June 2008

The Borealis basin and the martian crustal dichotomy
Jeffery C. Andrews-Hanna et al.
25 June 2008

Mega-impact formation of the Mars hemispheric dichotomy
Margarita M. Marinova et al.
25 June 2008

Implications of an impact origin for the Martian hemispheric Dichotomy
Francis Nimmo et al.
25 June 2008

Link: Nature Magazine - Cosmic Impacts

Evidence Of Massive Asteroid Impact On Mars Supported By Computer Simulations

From the ScienceDaily Article...

The dramatic differences between the northern and southern hemispheres of Mars have puzzled scientists for 30 years. One of the proposed explanations--a massive asteroid impact--now has strong support from computer simulations carried out by two groups of researchers. Planetary scientists at the University of California, Santa Cruz, were involved in both studies, which appear in the June 26 issue of Nature.

"It's a very old idea, but nobody had done the numerical calculations to see what would happen when a big asteroid hits Mars," said Francis Nimmo, associate professor of Earth and planetary sciences at UCSC and first author of one of the papers.

Nimmo's group found that such an impact could indeed produce the observed differences between the Martian hemispheres. The other study used a different approach and reached the same conclusion. Nimmo's paper also suggests testable predictions about the consequences of the impact.

The so-called hemispheric dichotomy was first observed by NASA's Viking missions to Mars in the 1970s. The Viking spacecraft revealed that the two halves of the planet look very different, with relatively young, low-lying plains in the north and relatively old, cratered highlands in the south. Some 20 years later, the Mars Global Surveyor mission showed that the crust of the planet is much thicker in the south and also revealed magnetic anomalies present in the southern hemisphere and not in the north.

"Two main explanations have been proposed for the hemispheric dichotomy--either some kind of internal process that changed one half of the planet, or a big impact hitting one side of it," Nimmo said. "The impact would have to be big enough to blast the crust off half of the planet, but not so big that it melts everything. We showed that you really can form the dichotomy that way."

Nimmo's group includes UCSC graduate student Shawn Hart, associate researcher Don Korycansky, and Craig Agnor of Queen Mary University, London. The other paper is by Margarita Marinova and Oded Aharonson of the California Institute of Technology and Erik Asphaug, professor of Earth and planetary sciences at UCSC.

The quantitative model used by Nimmo's group calculated the effects of an impact in two dimensions. Asphaug's group used a different model to calculate impacts in three dimensions, but with lower resolution (i.e., less detail in the simulation).

"The two approaches are very complementary; putting them together gives you a complete picture," Nimmo said. "The two-dimensional model provides high resolution, but you can only look at vertical impacts. The three-dimensional model allows nonvertical impacts, but the resolution is lower so you can't track what happens to the crust."

Most planetary impacts are not head-on, Asphaug said. His group found a "sweet spot" of impact conditions that result in a hemispheric dichotomy matching the observations. Those conditions include an impactor about one-half to two-thirds the size of the Moon, striking at an angle of 30 to 60 degrees.

"This is how planets finish their business of formation," Asphaug said. "They collide with other bodies of comparable size in gargantuan collisions. The last of those big collisions defines the planet."

According to Nimmo's analysis, shock waves from the impact would travel through the planet and disrupt the crust on the other side, causing changes in the magnetic field recorded there. The predicted changes are consistent with observations of magnetic anomalies in the southern hemisphere, he said.

In addition, new crust that formed in the northern lowlands would be derived from deep mantle rock melted by the impact and should have significantly different characteristics from the southern hemisphere crust. Certain Martian meteorites may have originated from the northern crust, Nimmo said. The study also suggests that the impact occurred around the same time as the impact on Earth that created the Moon.

This research was funded by NASA.

25 June 2008

Link: ScienceDaily

Link: Nature Magazine Article

Link: Computer simulation

Link: article

Link: University of Santa Cruz Press Release

Link: MIT Press Release

Link: National Public Radio (NPR) Story: "Mars May Have Been Struck by Massive Object"

U.S. Senate Committee on Commerce, Science, and Transportation passes NASA Authorization Legislation: NEO Inclusion

The U.S. Senate's Committee on Commerce, Science, and Transportation just passed "The National Aeronautics and Space Administration Authorization Act of 2008" (essnetailly its version of H.R. 6063 that passed in the House). The legislation seems to have multiple elements (similar to H.R. 6063). The press release from the committee indicates some support of NEO activity, specifically the following...

The bill also includes studies on field center leasing practices and project and work allocation; an interagency study of commercial space launch range facilities; a study on the impact of export control policies related to the aerospace industry; and an expression of support for the Near-Earth Object Survey to detect and identify near-Earth objects.

Link: Press Release (Commerce Committee Approves National Aeronautics and Space Administration Authorization Act of 2008)

22 June 2008

New Discovery Channel Canada Documentary: "Asteroid Trackers"

Monday, June 30 2008 at 7pm ET/8pm PT and simulcast on Discovery HD at 7pm ET/4pm PT, Discovery Channel Canada presents a new documentary on asteroid mitigation. Discovery Channel segment producer Barb Ustina is the person behind this new documentary.

From the show website...

Discovery Channel Scours the Skies for Near-Earth Objects on a Collision Course with Our Planet in Asteroid Trackers, June 30

Just after 7 a.m. on June 30, 1908, a mysterious explosion occurred in the remote area of Tunguska in Siberia. With only overturned trees and singed branches as evidence of this event, scientists are still uncovering data about that collision - and other asteroids - that may be headed straight for us.

On the 100th anniversary of the Tunguska event, Discovery Channel presents Asteroid Trackers, a one-hour original Canadian special that looks at efforts to track Apophis, an asteroid due to come dramatically - and dangerously - close to Earth in 2029 and again in 2036.

Premiering Monday, June 30 at 7pm ET/8pm PT and simulcast on Discovery HD at 7pm ET/4pm PT, this compelling special delves into various facets of asteroid research around the world.

Shot entirely in High Definition and hosted by Daily Planet's Jay Ingram on location from a crater site in Arizona, Asteroid Trackers reveals how experts are attempting to protect the world from near-Earth objects (NEOs). Whether it's determining the composition of the asteroids so they can be destroyed effectively or swarming them with reflective mirrors, find out which deflection methods are pushing the boundaries of technology to protect the planet from yet another cosmic collision.

Highlights from Asteroid Trackers include:

Using one of the world's fastest super computers, Sandia National Laboratories nuclear research investigator Mark Boslough has demonstrated that the asteroid which blasted Tunguska 100 years ago was smaller than experts previously thought. This discovery has strong implications about the size of an asteroid and the amount of damage it can cause. It also begs the question: Do we have more to fear from the numerous small asteroids in our solar system than from the thousands of big ones experts have already identified?

Based on craters studied so far, the planet has been hit by a large asteroid approximately every 100 years, which means we may be due for another one soon. Watch as University of Arizona's violent impact specialist Jay Melosh demonstrates his idea to change an asteroid's course. Using a very simple technique, Melosh is proposing a new way of preventing another cosmic collision - provided we have 10 years' notice.

Most asteroids are discovered by well established research teams, but in an effort to identify and track rogue asteroids, amateur astronomers are also very helpful. Meet Roy Tucker, a passionate astronomer who keeps his eye on the sky in a Tucson, Arizona, suburb. Tucker and his friend were the first to identify Apophis, an asteroid due to come perilously close to Earth in 2029, and possibly again in 2036. See how his constant communication with Harvard Smithsonian's Minor Planet Centre helps experts keep track of dangerous near-Earth objects.

Link: Discovery Channel Canada Show Link

Link: Discovery Channel Press Release

U.S. Congressman Dana Rohrabacher's Comments on Use of Russian Radar for Asteroid Investigations

U.S. Congressman Dana Rohrabacher's recent visit to Russia had some space related themes (including NEOS). One of the items that the Congressman discussed was the use of Russia's RT 70 radar for asteroid tasks. Some Russian news outlets seem to have taken this to indicate NASA's intention to use this radar, which may not be the case since I am unsure if that is exactly what the Congressman probably suggested. This seems to be getting some attention from Russian News agencies. Selections from various articles follow...

U.S.-Russian cooperation in space was discussed during U.S. House of Representatives Congressman Dana Rohrabacher's visit to the rocket and space corporation Energia in Moscow, Russian space agency Roscosmos reported.

Rohrabacher met with Energia head Vitaly Lopota for talks that were also attended by NASA representatives, Roscosmos said on its website.

"The parties expressed the opinion that cooperation between the two space powers in major space projects, including the International Space Station (ISS), is very effective, while a flight to Mars could give the generations to come a lot more than manned flights to the Moon," Roscosmos said.

The talks dealt with the safety of Soyuz flights, the operation of the ISS and the future of Russian-U.S. cooperation in space, it said. "U.S. Congressman Rohrabacher said that he personally did not doubt the reliability and flight safety of the Russian manned spacecraft Soyuz," Roscosmos said.

"The U.S. congressman also said that Russia and the United States could launch large-scale space projects in the future. A Moon base project and the protection of the earth from asteroids deserve priority attention, he said," according to the Roscosmos posting.

"Russia, U.S. Could Jointly Run Space Projects"
04 June 2008

Link: redOrbit Article

Congressmen suggested a Russian telecommunication center in the Primorye Territory, in the Far East, could be used for early warning and detection of dangerous asteroids.

Perminov said the RT 70 radar deployed in the town of Galenki near Ussuriisk (the second largest city in Primorye) is a facility used by Russia's Space Forces.

Link: RIA Novosti Article

The House of Representatives of the US Congress approved the NASA budget in the amount o 20.2 billion dollars Wednesday, RIA Novosti reports. The budget bill contains an amendment about the strengthening of NASA’s cooperation with Russia and other countries within the scope of the program which develops protection against a possible asteroid impact. US congressmen plan to use Russia’s RT-70 radar for the purpose.

Anatoly Perminov, the head of Russia’s Space Agency Roscosmos, told RIA Novosti that the agency positively estimated the initiative from the US Congress. The official said that it could be possible to make a definitive decision on the matter only with the participation of the Russian Defense Ministry. Anatoly Perminov added that the asteroid danger issue should be discussed on the top presidential level.

"NASA to use Russian radar to save USA from asteroids"
19 June 2008

Link: Pravda Article

Additional Notes on H.R. 6063

Here are some additional items on H.R. 60603 related to NEOs not mentioned in the previous post. We will see how the Senate reacts to this and then the final compromise legislation. Specific items of interest include the following:

1. Authorizes $2,000,000 to continue planetary radar operations at the Arecibo Observatory in support of the Near-Earth Object program

2. In SEC. 1106. INNOVATION PRIZES. there were comments related to the use of innovation prizes (the NASA Centennial Challenges program). There was a specific item that stated the following:

(a) In General- Prizes can play a useful role in encouraging innovation in the development of technologies and products that can assist NASA in its aeronautics and space activities, and the use of such prizes by NASA should be encouraged.

(b) Amendments- Section 314 of the National Aeronautics and Space Act of 1958 is amended--

(1) by amending subsection (b) to read as follows:

`(b) Topics- In selecting topics for prize competitions, the Administrator shall consult widely both within and outside the Federal Government, and may empanel advisory committees. The Administrator shall give consideration to prize goals such as the demonstration of the ability to provide energy to the lunar surface from space-based solar power systems, demonstration of innovative near-Earth object survey and deflection strategies, and innovative approaches to improving the safety and efficiency of aviation systems.'; and

(2) in subsection (i)(4) by striking `$10,000,000' and inserting `$50,000,000'.

1st IAA Planetary Defense Conference: 27-29 April 2009, Granada, Spain

Following on the 2004 and 2007 Planetary Defense Conferences, there will be an international conference in 2009 on planetary defense.

The 1st IAA Planetary Defense Conference: Protecting Earth from Asteroids will be held in 2009. This will be a three-day conference, sponsored by the International Academy of Astronautics (IAA) and the European Space Agency, and will be held in Granada, Spain on Monday through Wednesday, April 27-29, 2009.

More Backgound on Study from Some Within NASA for a Human Mission to An Asteroid using Constellation Elements

More background on the study by some within NASA for a human mission to an asteroid...selections from the article...

The B612 Foundation proposes a rendezvous with a space rock for weeks or months, during which the robot spacecraft would act as a “gravity tractor,” using its own minuscule gravitational pull to tug the asteroid onto a new course. While B612 spread its message, Ed Lu went on to spend six months aboard the International Space Station. Three months after his return to Earth, in January 2004, the Bush administration announced its Vision for Space Exploration, an ambitious call to send astronauts beyond Earth orbit for the first time since 1972. While NASA set up Constellation and began focusing on the lunar return, targeted for 2020, Lu and the Asteroid Underground quietly pondered other possibilities.

“When NASA unveiled the concepts of the Ares I and V launch vehicles and [the] Orion [crew capsule],” remembers Lu, “I started wondering, ‘Hey, we have these rockets at our disposal. What else can we do?’ ”

By the summer of 2006, Lu, Tom Jones, and Dave Korsmeyer, an engineer at NASA’s Ames Research Center who specializes in celestial mechanics, were conferring regularly with more than a dozen colleagues around the country, asking about the capabilities of Constellation and writing papers. NASA agreed to fund a feasibility study through its Advanced Projects Office that would examine how to use the Orion and Ares hardware to send people to a near-Earth asteroid. Korsmeyer managed the group. After many phone calls and e-mails among the 17 members of the study team, the first meeting took place at the Johnson Space Center in Houston in August 2006. Subsequent gatherings, about one per month, were convened at various NASA centers around the country. By the end of the year, the group had come to the conclusion that NASA’s new hardware could in fact carry humans to a NEO.

In the Asteroid Underground, [Bob] Farquhar is something of an elder statesman and is known for his outspokenness. Having taken part in a recent feasibility study for the International Academy of Astronautics that looked at different options for moving beyond Earth orbit, he doesn’t like the idea of making do with existing Constellation hardware for a stripped-down asteroid mission. “You’d need a transfer vehicle,” he says. “Something big and roomy. And you don’t want it in low Earth orbit all the time.” Instead, he would park an interplanetary, or inter-asteroidal, transfer vehicle at the L2 libration point, about a million miles outside Earth’s orbit, where the gravitational pulls of the sun and Earth are balanced. The transfer vehicle would pick up the crew members in Earth orbit, take them to an asteroid (or, someday, Mars), and then, at journey’s end, return them to Earth orbit.

Dave Korsmeyer has been optimistic about NASA’s interest in asteroids ever since he briefed Constellation manager Jeff Hanley on his study group’s findings in February 2007. “Hanley said, ‘This is great!’ He said the best thing for us to know is that this [Constellation] architecture goes to more than one place instead of just ’round the block.

“Every month since, we’ve been giving a briefing to someone, and not because we’re pushing it. They’re asking for it.” A more detailed study, he says, may be forthcoming.

Rob Landis, a member of the study group with experience in mission control, says, “Apollo 8 was never intended to go to the moon. But NASA said, ‘What if we go anyway?’ That was a huge, quantum leap. I’d say that an asteroid mission is the Apollo 8 of the next generation—before jumping off to Mars, before dipping our toes deeper in that cosmic ocean.”

"The Million Mile Mission: A small band of believers urges NASA to take its next step—onto an asteroid."
Michael Klesius
Air & Space Magazine
01 July 2008

Link: Air & Space Magazine Article

21 June 2008

ESA Marco Polo Mission Overview from June 2008 Workshop (and presentations)

From the announcement of the Marco Polo Workshop, a short overview of the Marco Polo mission. Please see the announcement that follows as well as the links for the presentations given at the June 2008 Workshop. Some interesting points observed from the presentations include that NASA is potentially interested in contributing to Marco Polo as a Mission of Opportunity ($35M). This comes from the OSIRIS mission overview presentation (available at the workshop site, see link below).

From the overview of the June 2008 Workshop, there is a good overview of the Marco Polo mission...

Marco Polo is a Near-Earth Object sample return mission studied within the Cosmic Vision programme. It was proposed by Antonella Barucci and a team of several hundred scientists in Europe to ESA in 2007 and is currently undergoing an assessment study.

Marco Polo was proposed in response to ESA's call for mission proposals as part of the new Cosmic Vision programme, suggesting missions with a launch date between 2015 and 2025. The lead proposers are Antonella Barucci from the Observatoire de Paris-Meudon and M. Yoshikawa from the Japanese space agency JAXA. They were supported by a core team of six scientists in Europe, two scientists in Japan, and one in the USA. A total of 436 scientists from countries all over the world support the proposal.

Small bodies in the solar system are leftover building blocks of the formation of the solar system. They offer clues to the chemical mixture from which the planets formed some 4.6 billion years ago. Also, current exobiological scenarios for the origin of life invoke an exogenous delivery of organic matter to the early Earth: it has been proposed that primitive bodies could have brought these complex organic molecules capable of triggering the pre-biotic synthesis of biochemical compounds on the early Earth. Moreover, collisions of NEOs with the Earth pose a finite hazard to life. For all these reasons, the exploration of such objects is particularly interesting and urgent.

The principal scientific objective of the Marco Polo mission is to return unaltered material from a NEO, for analysis in terrestrial laboratories, thereby obtaining measurements that cannot yet be performed from a robotic spacecraft (e.g. dating the major events in the history of a sample).

Moreover, the mission will enable us to:

1. Determine the physical and chemical properties of the target body, which are representative of the planetesimals present in the early solar nebula
2. Identify the major events (e.g. agglomeration, heating, aqueous alteration, solar wind interaction) which influenced the history of the target
3. Determine the elemental and mineralogical properties of the target body and the geological context of the surface
4. Search for pre-solar material yet unknown in meteoritic samples
5. Investigate the nature and origin of organic compounds on the target body
6. Identify organic compounds which may reveal the origin of pre-biotic molecules
7. Understand the role of minor body impacts in the origin and evolution of life on Earth

Link: Marco Polo June 2008 Workshop Announcement

Link: June 2008 Workshop Presentations

Link: LPSI Abstract on Marco Polo Mission - PDF

Initial Russian response to NASA House Authorization Act actions on NEO Threat

"Russia's space agency backs U.S. asteroid control plan"
19 June 1008

MOSCOW, June 19 (RIA Novosti) - Russia's Federal Space Agency has endorsed a proposal by the U.S. House of Representatives that a Russian radar station be used to detect dangerous asteroids, Roscosmos head said on Thursday.

"I generally approve and support the U.S. initiative," Anatoly Perminov said in a telephone interview with RIA Novosti. "As for the asteroid danger, it really exists, and needs to be dealt with through the joint efforts of all states concerned."

On Wednesday, the U.S. House of Representatives approved NASA's $20.2 billion budget for 2009, committing the U.S. to cooperation with Russia and other countries to avoid asteroid threats.

Congressmen suggested a Russian telecommunication center in the Primorye Territory, in the Far East, could be used for early warning and detection of dangerous asteroids.

Perminov said the RT 70 radar deployed in the town of Galenki near Ussuriisk (the second largest city in Primorye) is a facility used by Russia's Space Forces.

"This matter is more a question for the Defense Ministry, but we will back the project as an idea," he said.

Link: RIA Novosti Article

Chart: 10 Scariest Asteroid Attacks on Earth: The Near Hits and Approaching Terrors

Interesting data visualization about potential NEO threats.

Link: io9 article

OMB Response to H.R. 6063: Implications for NEO aspects aspects of the legislation

As a follow-up to the U.S. House of Representatives, the White House, through its Office of Management and Budget (OMB), has responded to the U.S. House of Representatives H.R. 6063 resolution. The statement from the OMB has elements related to multiple items on NASA’s agenda including the human lunar exploration architecture, retirement of the Space Shuttle, extension of the International Space Station (ISS). The statements relate to Congress directing NASA (and thus the Executive branch) on specific actions, these may also relate to the reports and actions related to NEOs. We must anticipate the negotiations of the OMB and Congress on these NEO items in the House resolution. Specific language of the OMB statements includes the following:

In addition, H.R. 6063 directs several specific activities under the assumption that additional funding will be appropriated, making it likely they will become unfounded….Directing activities in this manner would severely disrupt the budgets for NASA’s ongoing, carefully-balanced programs and Centers linked to other high-priority goals and activities. For this reason and in view of associated problematic policy implications, the following requirements should either be removed from the bill or appropriately modified:… and (5) prescribing specific roles and responsibilities regarding NASA’s work with various advisory and external review committees and other Federal agencies that the Administration believes would be problematic and duplicative of already well-established roles and responsibilities.

Finally, in addition to the significant concerns highlighted above that must be satisfactorily addressed prior to final congressional action, the Administration has an overarching concern about the highly prescriptive nature of the bill and the significant number of reports and studies that this legislation would require. The Administration understands the need for timely information for Congress to conduct its oversight responsibilities; however, the burden that would be placed on various agencies of the Executive Branch, including NASA, is of concern. The Administration looks forward to working with Congress to modify these aspects of the bill.

June 10, 2008 (House Rules)
H.R. 6063 – National Aeronautics and Space Administration Authorization Act of 2008

Link: OMB Statement (from the White House) PDF

Link: OMB Statement (from the White House) Text

U.S. House of Representatives NASA Reauthorization Act (H.R. 6063): Major Updates

United States federal agencies go through an authorization and funding process wherein two branches of government (Legislative and Executive) within the U.S. have to agree. One of the parts of this activity every year is the legislative authorities giving their view. Recently, the United State House of Representatives passed their initial looks at NASA's priorities and budget. This legislation is called H.R. 6063 - National Aeronautics and Space Administration Authorization Act of 2008. Besides issues related to NASA's human lunar exploration plans (Orion, Constellation, technology development, space station continuation, and space science), there are several mandates and issues addressed in this legislation devoted to planetary defense. Let us take a moment to examine them a little further.

The following sections of the legislation refer to NEOs…



The Congress reaffirms the policy direction established in the National Aeronautics and Space Administration Authorization Act of 2005 (Public Law 109-155) for NASA to detect, track, catalogue, and characterize the physical characteristics of near-Earth objects equal to or greater than 140 meters in diameter. NASA's Near-Earth Object program activities will also provide benefits to NASA's scientific and exploration activities.


Congress makes the following findings:
(1) Near-Earth objects pose a serious and credible threat to humankind, as many scientists believe that a major asteroid or comet was responsible for the mass extinction of the majority of the Earth's species, including the dinosaurs, nearly 65,000,000 years ago.
(2) Several such near-Earth objects have only been discovered within days of the objects' closest approach to Earth and recent discoveries of such large objects indicate that many large near-Earth objects remain undiscovered.
(3) Asteroid and comet collisions rank as one of the most costly natural disasters that can occur.
(4) The time needed to eliminate or mitigate the threat of a collision of a potentially hazardous near-Earth object with Earth is measured in decades.
(5) Unlike earthquakes and hurricanes, asteroids and comets can provide adequate collision information, enabling the United States to include both asteroid-collision and comet-collision disaster recovery and disaster avoidance in its public-safety structure.
(6) Basic information is needed for technical and policy decision making for the United States to create a comprehensive program in order to be ready to eliminate and mitigate the serious and credible threats to humankind posed by potentially hazardous near-Earth asteroids and comets.
(7) As a first step to eliminate and to mitigate the risk of such collisions, situation and decision analysis processes, as well as procedures and system resources, must be in place well before a collision threat becomes known.

The Administrator shall issue requests for information on-

(1) a low-cost space mission with the purpose of rendezvousing with and characterizing the Apophis asteroid, which scientists estimate will in 2029 pass at a distance from Earth that is closer than geostationary satellites; and

(2) a medium-sized space mission with the purpose of detecting near-Earth objects equal to or greater than 140 meters in diameter.


The Director of OSTP shall--
(1) develop a policy for notifying Federal agencies and relevant emergency response institutions of an impending near-Earth object threat, if near term public safety is at stake; and
(2) recommend a Federal agency or agencies to be responsible for protecting the Nation from a near-Earth object that is anticipated to collide with Earth and implementing a deflection campaign, in consultation with international bodies, should one be required.


The Administrator shall maintain a planetary radar that is, at minimum, comparable to the capability provided through the NASA Deep Space Network Goldstone facility.


Congress reiterates its support for the use of the Arecibo Observatory for NASA-funded near-Earth object-related activities. The Administrator shall ensure the availability of the Arecibo Observatory's planetary radar to support these activities until the National Academies' review of NASA's approach for the survey and deflection of near-Earth objects, including a determination of the role of Arecibo, that was directed to be undertaken by the Fiscal Year 2008 Omnibus Appropriations Act, is completed.

Link: H.R. 6063 - National Aeronautics and Space Administration Authorization Act of 2008

Link: PDF - National Aeronautics and Space Administration Authorization Act of 2008 (Engrossed as Agreed to or Passed by House)[H.R.6063.EH]

Link: Text - National Aeronautics and Space Administration Authorization Act of 2008 (Engrossed as Agreed to or Passed by House)[H.R.6063.EH]

Near Earth Object Surveillance Satellite (NEOSSat): Small Canadian Spacecraft to Search for Asteroids

Near Earth Object Surveillance Satellite (NEOSSat) is a 60-kilogram Canadian microsatellite, costing reportedly $11.5M CAD (including launch), that will search for asteroids. Alan Hildebrand of the University of Calgary is one of two principal scientists for the satellite. This mission has been in concept study and development for many years.

An abstract on the spacecraft indicates the following:
"NEOSSat will be ~50 kg deploying a telescope similar to the 15-cm aperture f5.88 Maksutov on MOST (Microvariability and Oscillations of Stars). The spacecraft will be 3-axis stabilized with a pointing precision of ~2 arcseconds in a ~100 second exposure. The NEOSSat mission has completed Phase A with launch currently anticipated in 2009, and will be the first in a series of microsatellites based upon a multi-mission bus concept developed by the Canadian Space Agency in cooperation with Defence Research and Development Canada. The spacecraft will be deployed into a Sun – synchronous orbit similar to that occupied by the MOST spacecraft."

A paper will be given at this year's Small Satellite Conference in Logan, Utah on this satellite. The Paper is entitled: "NEOSSAT: A Collaborative Microsatellite Project for Space Based Object Detection" by William Harvey (CSA) and Tony Morris (Defense Research and Development Canada).

Link: LPSI Abstract

Link: AIAA Technical Paper

Link: Ottawa Citizen Article

Link: article (from 25 August 2000)

Link: Small Conference Conference at Utah State University

Asteroid Deflection Research Center (ADRC) recently established at Iowa State University

A new center devoted for research on NEO mitigation was established at Iowa State University. Dr. Bong Wie, a professor of Aerospace Engineering at Iowa State University, is responsible for the center. Here are some quotes from the press release...

An Asteroid Deflection Research Center (ADRC) has been established on the Iowa State campus to bring researchers from around the world to develop asteroid deflection technologies. The center was signed into effect in April by the Office of the Executive Vice President and Provost.

“In the early 1990s, scientists around the world initiated studies to assess and devise methods to prevent near-Earth objects from striking Earth,” said Bong Wie, the Vance D. Coffman Chair Professor in Aerospace Engineering and director of the center. “However, it is now 2008, and there is no consensus on how to reliably deflect them in a timely manner,” he noted.

Wie, whose research expertise includes space vehicle dynamics and control, modeling and control of large space structures, and solar sail flight control system development and mission design, joined the Iowa State faculty last August. “I am very happy that Professor Bong Wie has joined the faculty at ISU,” said Elizabeth Hoffman, executive vice president and provost. “His work on asteroid deflection is exciting and of great importance.”

The ADRC will host an International Symposium on Asteroid Deflection Technology in fall 2008. Scientists and engineers from NASA, the European Space Agency, academia, and the aerospace industry will be invited to the Iowa State campus to formulate a roadmap for developing asteroid deflection technologies.

“Developing technologies that can be used to prevent or mitigate threats from asteroids while also advancing space exploration is a challenge we accept as we work to assure a high quality of life for future generations,” said Mark J. Kushner, dean of Iowa State’s College of Engineering. “This research center serves as an excellent opportunity to provide leadership on an issue that has worldwide implications.”

Both high-energy nuclear explosions and low-energy non-nuclear alternatives will be studied as deflection techniques. The nuclear approach, which is often assessed to be 10–100 times more effective than non-nuclear approaches as stated in NASA’s 2007 report to Congress, will be researched to verify its effectiveness and determine its practical viability, according to Wie.

“A 20-meter (66 feet) standoff distance is often mentioned in the literature for a maximum velocity change of a 1-kilometer (0.6 mile) asteroid. However, we have to determine how close the nuclear explosion must be to effectively change the orbital trajectories of asteroids of different types, sizes, and shapes,” Wie explained. “We will develop high-fidelity physical models to reliably predict the velocity change and fragmentation caused by a nuclear standoff explosion.”

The non-nuclear alternatives include kinetic impactors and slow-pull gravity tractors. Wie, who has previously worked on solar sail technology as applied to asteroid deflection, will present his recent study, “Multiple gravity tractors in halo orbits for towing a target asteroid,” at the American Institute of Aeronautics and Astronautics Astrodynamics Specialists Conference in August. His paper has been accepted for publication in the AIAA Journal of Guidance, Control, and Dynamics.

Link: Press Release

20 June 2008

Dave Morrison's response to Greeg Easterbrook's article

Dave Morrison in his NEO News has some comments on the Easterbrook article entitled "The Sky is Falling." Here are Mr. Morrison's comments...

NEO News (05/22/08) Is the Sky Falling?

The June issue of The Atlantic features a long article on the impact threat and how to defend against asteroids, called "The Sky is Falling". The author is Gregg Easterbrook, a contributing editor to both The Atlantic and The New Republic. This is one of the most visible and potentially influential articles on NEO impact issues to be published in several years.

Easterbrook has written an advocacy article, not an objective discussion of this topic. His primary thesis (which I will not discuss further here) is that NASA should make asteroid defense a major part of its mission, perhaps replacing current emphasis on human flight to the Moon. To support this thesis, Easterbrook has painted the impact hazard as severe and has chosen examples that suggest that that the risk is much greater, by factors of up to a thousand, than in the "conventional wisdom". I will comment briefly on some of this evidence. I thank Bill Bottke, Mark Boslough, Clark Chapman, Al Harris, Michael Paine, Rusty Schweickart, and other colleagues for their email comments on this article.

Here are some of the rhetorical techniques used by Easterbrook to dramatize the threat.

The article repeatedly states that perception of the threat is increasing, but it does not indicate the baseline against which to measure this supposed increase. While it is certainly true that we are much more aware of the impact threat than we were a century ago, or even 50 years, it is not true that the scientific perception of the threat has increased in the past decade. In fact, current risk estimates are a factor or 2-3 lower than the frequently-quoted values published by Chapman and Morrison in 1994 and described in the NASA Spaceguard Report. The science threat estimate, which is primarily what Easterbrook is discussing, has thus been stable and even decreased over the past 15 years. However, it is true that the public perception has been increasing.

Of the various ways that the population and impact rate of NEAs are calculated, Easterbrook mentions only estimates based on the number of craters on land areas of Earth. There is no reference to the astronomical surveys that today provide the best population estimates. He asserts that until very recently the estimates of impact frequency, based on land craters, neglected impacts into the ocean or airbursts like Tunguska; when ocean impacts and airbursts are considered, the impact frequency jumps at least a factor of ten. This is wrong. Gene Shoemaker and others, who began in the 1980s to use terrestrial craters to estimate impact rates, counted craters per unit area (thus correcting for unobserved areas such as the ocean) and also allowed for airbursts that do not produce craters. Since the early 1990s, impact rates derived from terrestrial craters, lunar craters, and astronomical surveys have been consistent.

There is one reference to survey results: Easterbrook writes "in 1980, only 86 [NEOs] were known to exist. By 1990, the figure had risen to 170; by 2000, it was 921, as of this writing, it was 5388." He apparently takes these numbers as an indication that "near-Earth space rocks are more numerous than once was thought." An analogy illustrates the flaws in this logic: You move to a town of 50,000 and initially know only a handful of your neighbors. After a decade the number of your acquaintances has increased to several thousand. But this does not mean that the town has grown; indeed, its population may have fallen from 50,000 to 40,000.

Here is another paragraph that raises questions. He writes "A generation ago, the standard assumption was that a dangerous object would strike the Earth perhaps once in million years. By the mid-1990s, researchers began to say that the threat was greater: perhaps a strike every 300,000 years. This winter I asked William Ailor Š what he thought the risk was. Ailor's answer: a one-in-ten chance per century of a dangerous space-object-strike." Most readers of "NEO News" will recognize one-in-a-million-years as the estimate for a civilization-threatening impact, by a NEA 1-2 km across (energy a million megatons). The one-in-a-thousand-year number quoted by Ailor is for a Tunguska class airburst of 10 megatons, ten thousand times smaller. If we compare impacts of the same size, then the current estimate for the million-megaton impact is once in 2 million years, and the earlier (1994) estimate for Tunguska is once in a couple of centuries. Both calculated frequencies are consistent with each other, and both have gone down with our increasing knowledge, not up.

One could make many more criticisms, but these give the flavor of Easterbrook's rhetorical style. You can judge for yourself in reading his article, below.

David Morrison

Article, "The Sky Is Falling" by Gregg Easterbrook, The Atlantic, June 2008

Article from Gregg Easterbrook in The Atlantic on the threat from asteroids and comets...entire article below:

Breakthrough ideas have a way of seeming obvious in retrospect, and about a decade ago, a Columbia University geophysicist named Dallas Abbott had a breakthrough idea. She had been pondering the craters left by comets and asteroids that smashed into Earth. Geologists had counted them and concluded that space strikes are rare events and had occurred mainly during the era of primordial mists. But, Abbott realized, this deduction was based on the number of craters found on land-and because 70 percent of Earth's surface is water, wouldn't most space objects hit the sea? So she began searching for underwater craters caused by impacts rather than by other forces, such as volcanoes. What she has found is spine-chilling: evidence that several enormous asteroids or comets have slammed into our planet quite recently, in geologic terms. If Abbott is right, then you may be here today, reading this magazine, only because by sheer chance those objects struck the ocean rather than land.

Abbott believes that a space object about 300 meters in diameter hit the Gulf of Carpentaria, north of Australia, in 536 A.D. An object that size, striking at up to 50,000 miles per hour, could release as much energy as 1,000 nuclear bombs. Debris, dust, and gases thrown into the atmosphere by the impact would have blocked sunlight, temporarily cooling the planet-and indeed, contemporaneous accounts describe dim skies, cold summers, and poor harvests in 536 and 537. "A most dread portent took place," the Byzantine historian Procopius wrote of 536; the sun "gave forth its light without brightness." Frost reportedly covered China in the summertime. Still, the harm was mitigated by the ocean impact. When a space object strikes land, it kicks up more dust and debris, increasing the global-cooling effect; at the same time, the combination of shock waves and extreme heating at the point of impact generates nitric and nitrous acids, producing rain as corrosive as battery acid. If the Gulf of Carpentaria object were to strike Miami today, most of the city would be leveled, and the atmospheric effects could trigger crop failures around the world.

What's more, the Gulf of Carpentaria object was a skipping stone compared with an object that Abbott thinks whammed into the Indian Ocean near Madagascar some 4,800 years ago, or about 2,800 B.C. Researchers generally assume that a space object a kilometer or more across would cause significant global harm: widespread destruction, severe acid rain, and dust storms that would darken the world's skies for decades. The object that hit the Indian Ocean was three to five kilometers across, Abbott believes, and caused a tsunami in the Pacific 600 feet high-many times higher than the 2004 tsunami that struck Southeast Asia. Ancient texts such as Genesis and the Epic of Gilgamesh support her conjecture, describing an unspeakable planetary flood in roughly the same time period. If the Indian Ocean object were to hit the sea now, many of the world's coastal cities could be flattened. If it were to hit land, much of a continent would be leveled; years of winter and mass starvation would ensue.

At the start of her research, which has sparked much debate among specialists, Abbott reasoned that if colossal asteroids or comets strike the sea with about the same frequency as they strike land, then given the number of known land craters, perhaps 100 large impact craters might lie beneath the oceans. In less than a decade of searching, she and a few colleagues have already found what appear to be 14 large underwater impact sites. That they've found so many so rapidly is hardly reassuring.

Other scientists are making equally unsettling discoveries. Only in the past few decades have astronomers begun to search the nearby skies for objects such as asteroids and comets (for convenience, let's call them "space rocks"). What they are finding suggests that near-Earth space rocks are more numerous than was once thought, and that their orbits may not be as stable as has been assumed. There is also reason to think that space rocks may not even need to reach Earth's surface to cause cataclysmic damage. Our solar system appears to be a far more dangerous place than was previously believed.

The received wisdom about the origins of the solar system goes something like this: the sun and planets formed about 4.5 billion years ago from a swirling nebula containing huge amounts of gas and dust, as well as relatively small amounts of metals and other dense substances released by ancient supernova explosions. The sun is at the center; the denser planets, including Earth, formed in the middle region, along with many asteroids-the small rocky bodies made of material that failed to incorporate into a planet. Farther out are the gas-giant planets, such as Jupiter, plus vast amounts of light elements, which formed comets on the boundary of the solar system. Early on, asteroids existed by the millions; the planets and their satellites were bombarded by constant, furious strikes. The heat and shock waves generated by these impacts regularly sterilized the young Earth. Only after the rain of space objects ceased could life begin; by then, most asteroids had already either hit something or found stable orbits that do not lead toward planets or moons. Asteroids still exist, but most were assumed to be in the asteroid belt, which lies between Mars and Jupiter, far from our blue world.

As for comets, conventional wisdom held that they also bombarded the planets during the early eons. Comets are mostly frozen water mixed with dirt. An ancient deluge of comets may have helped create our oceans; lots of comets hit the moon, too, but there the light elements they were composed of evaporated. As with asteroids, most comets were thought to have smashed into something long ago; and, because the solar system is largely void, researchers deemed it statistically improbable that those remaining would cross the paths of planets.

These standard assumptions-that remaining space rocks are few, and that encounters with planets were mainly confined to the past-are being upended. On March 18, 2004, for instance, a 30-meter asteroid designated 2004 FH-a hunk potentially large enough to obliterate a city-shot past Earth, not far above the orbit occupied by telecommunications satellites. (Enter "2004 FH" in the search box at Wikipedia and you can watch film of that asteroid passing through the night sky.) Looking at the broader picture, in 1992 the astronomers David Jewitt, of the University of Hawaii, and Jane Luu, of the Massachusetts Institute of Technology, discovered the Kuiper Belt, a region of asteroids and comets that starts near the orbit of Neptune and extends for immense distances outward. At least 1,000 objects big enough to be seen from Earth have already been located there. These objects are 100 kilometers across or larger, much bigger than whatever dispatched the dinosaurs; space rocks this size are referred to as "planet killers" because their impact would likely end life on Earth. Investigation of the Kuiper Belt has just begun, but there appear to be substantially more asteroids in this region than in the asteroid belt, which may need a new name.

Beyond the Kuiper Belt may lie the hypothesized Oort Cloud, thought to contain as many as trillions of comets. If the Oort Cloud does exist, the number of extant comets is far greater than was once believed. Some astronomers now think that short-period comets, which swing past the sun frequently, hail from the relatively nearby Kuiper Belt, whereas comets whose return periods are longer originate in the Oort Cloud.

But if large numbers of comets and asteroids are still around, several billion years after the formation of the solar system, wouldn't they by now be in stable orbits-ones that rarely intersect those of the planets? Maybe not. During the past few decades, some astronomers have theorized that the movement of the solar system within the Milky Way varies the gravitational stresses to which the sun, and everything that revolves around it, is exposed. The solar system may periodically pass close to stars or groups of stars whose gravitational pull affects the Oort Cloud, shaking comets and asteroids loose from their orbital moorings and sending them downward, toward the inner planets.

Consider objects that are already near Earth, and the picture gets even bleaker. Astronomers traditionally spent little time looking for asteroids, regarding them as a lesser class of celestial bodies, lacking the beauty of comets or the significance of planets and stars. Plus, asteroids are hard to spot-they move rapidly, compared with the rest of the heavens, and even the nearby ones are fainter than other objects in space. Not until the 1980s did scientists begin systematically searching for asteroids near Earth. They have been finding them in disconcerting abundance.

In 1980, only 86 near-Earth asteroids and comets were known to exist. By 1990, the figure had risen to 170; by 2000, it was 921; as of this writing, it is 5,388. The Jet Propulsion Laboratory, part of NASA, keeps a running tally at Ten years ago, 244 near-Earth space rocks one kilometer across or more-the size that would cause global calamity-were known to exist; now 741 are. Of the recently discovered nearby space objects, NASA has classified 186 as "impact risks" (details about these rocks are at And because most space-rock searches to date have been low-budget affairs, conducted with equipment designed to look deep into the heavens, not at nearby space, the actual number of impact risks is undoubtedly much higher. Extrapolating from recent discoveries, NASA estimates that there are perhaps 20,000 potentially hazardous asteroids and comets in the general vicinity of Earth.

There's still more bad news. Earth has experienced several mass extinctions-the dinosaurs died about 65 million years ago, and something killed off some 96 percent of the world's marine species about 250 million years ago. Scientists have generally assumed that whatever caused those long-ago mass extinctions-comet impacts, extreme volcanic activity-arose from conditions that have changed and no longer pose much threat. It's a comforting notion-but what about the mass extinction that occurred close to our era?

About 12,000 years ago, many large animals of North America started disappearing-woolly mammoths, saber-toothed cats, mastodons, and others. Some scientists have speculated that Paleo-Indians may have hunted some of the creatures to extinction. A millennia-long mini-Ice Age also may have been a factor. But if that's the case, what explains the disappearance of the Clovis People, the best-documented Paleo-Indian culture, at about the same time? Their population stretched as far south as Mexico, so the mini-Ice Age probably was not solely responsible for their extinction.

A team of researchers led by Richard Firestone, of the Lawrence Berkeley National Laboratory, in California, recently announced the discovery of evidence that one or two huge space rocks, each perhaps several kilometers across, exploded high above Canada 12,900 years ago. The detonation, they believe, caused widespread fires and dust clouds, and disrupted climate patterns so severely that it triggered a prolonged period of global cooling. Mammoths and other species might have been killed either by the impact itself or by starvation after their food supply was disrupted. These conclusions, though hotly disputed by other researchers, were based on extensive examinations of soil samples from across the continent; in strata from that era, scientists found widely distributed soot and also magnetic grains of iridium, an element that is rare on Earth but common in space. Iridium is the meteor-hunter's lodestar: the discovery of iridium dating back 65 million years is what started the geologist Walter Alvarez on his path-breaking theory about the dinosaurs' demise.

A more recent event gives further cause for concern. As buffs of the television show The X Files will recall, just a century ago, in 1908, a huge explosion occurred above Tunguska, Siberia. The cause was not a malfunctioning alien star-cruiser but a small asteroid or comet that detonated as it approached the ground. The blast had hundreds of times the force of the Hiroshima bomb and devastated an area of several hundred square miles. Had the explosion occurred above London or Paris, the city would no longer exist. Mark Boslough, a researcher at the Sandia National Laboratory, in New Mexico, recently concluded that the Tunguska object was surprisingly small, perhaps only 30 meters across. Right now, astronomers are nervously tracking 99942 Apophis, an asteroid with a slight chance of striking Earth in April 2036. Apophis is also small by asteroid standards, perhaps 300 meters across, but it could hit with about 60,000 times the force of the Hiroshima bomb-enough to destroy an area the size of France. In other words, small asteroids may be more dangerous than we used to think-and may do considerable damage even if they don't reach Earth's surface.

Until recently, nearly all the thinking about the risks of space-rock strikes has focused on counting craters. But what if most impacts don't leave craters? This is the prospect that troubles Boslough. Exploding in the air, the Tunguska rock did plenty of damage, but if people had not seen the flashes, heard the detonation, and traveled to the remote area to photograph the scorched, flattened wasteland, we'd never know the Tunguska event had happened. Perhaps a comet or two exploding above Canada 12,900 years ago spelled the end for saber-toothed cats and Clovis society. But no obvious crater resulted; clues to the calamity were subtle and hard to come by.

Comets, asteroids, and the little meteors that form pleasant shooting stars approach Earth at great speeds-at least 25,000 miles per hour. As they enter the atmosphere they heat up, from friction, and compress, because they decelerate rapidly. Many space rocks explode under this stress, especially small ones; large objects are more likely to reach Earth's surface. The angle at which objects enter the atmosphere also matters: an asteroid or comet approaching straight down has a better chance of hitting the surface than one entering the atmosphere at a shallow angle, as the latter would have to plow through more air, heating up and compressing as it descended. The object or objects that may have detonated above Canada 12,900 years ago would probably have approached at a shallow angle.

If, as Boslough thinks, most asteroids and comets explode before reaching the ground, then this is another reason to fear that the conventional thinking seriously underestimates the frequency of space-rock strikes-the small number of craters may be lulling us into complacency. After all, if a space rock were hurtling toward a city, whether it would leave a crater would not be the issue-the explosion would be the issue.

A generation ago, the standard assumption was that a dangerous object would strike Earth perhaps once in a million years. By the mid-1990s, researchers began to say that the threat was greater: perhaps a strike every 300,000 years. This winter, I asked William Ailor, an asteroid specialist at The Aerospace Corporation, a think tank for the Air Force, what he thought the risk was. Ailor's answer: a one-in-10 chance per century of a dangerous space-object strike.

Regardless of which estimate is correct, the likelihood of an event is, of course, no predictor. Even if space strikes are likely only once every million years, that doesn't mean a million years will pass before the next impact-the sky could suddenly darken tomorrow. Equally important, improbable but cataclysmic dangers ought to command attention because of their scope. A tornado is far more likely than an asteroid strike, but humanity is sure to survive the former. The chances that any one person will die in an airline crash are minute, but this does not prevent us from caring about aviation safety. And as Nathan Myhrvold, the former chief technology officer of Microsoft, put it, "The odds of a space-object strike during your lifetime may be no more than the odds you will die in a plane crash-but with space rocks, it's like the entire human race is riding on the plane."

Given the scientific findings, shouldn't space rocks be one of NASA's priorities? You'd think so, but Dallas Abbott says NASA has shown no interest in her group's work: "The NASA people don't want to believe me. They won't even listen."

NASA supports some astronomy to search for near-Earth objects, but the agency's efforts have been piecemeal and underfunded, backed by less than a tenth of a percent of the NASA budget. And though altering the course of space objects approaching Earth appears technically feasible, NASA possesses no hardware specifically for this purpose, has nearly nothing in development, and has resisted calls to begin work on protection against space strikes. Instead, NASA is enthusiastically preparing to spend hundreds of billions of taxpayers' dollars on a manned moon base that has little apparent justification. "What is in the best interest of the country is never even mentioned in current NASA planning," says Russell Schweick-art, one of the Apollo astronauts who went into space in 1969, who is leading a campaign to raise awareness of the threat posed by space rocks. "Are we going to let a space strike kill millions of people before we get serious about this?" he asks.

In January, I attended an internal NASA conference, held at agency headquarters, during which NASA's core goals were presented in a PowerPoint slideshow. Nothing was said about protecting Earth from space strikes-not even researching what sorts of spacecraft might be used in an approaching-rock emergency. Goals that were listed included "sustained human presence on the moon for national preeminence" and "extend the human presence across the solar system and beyond." Achieving national preeminence-isn't the United States pretty well-known already? As for extending our presence, a manned mission to Mars is at least decades away, and human travel to the outer planets is not seriously discussed by even the most zealous advocates of space exploration. Sending people "beyond" the solar system is inconceivable with any technology that can reasonably be foreseen; an interstellar spaceship traveling at the fastest speed ever achieved in space flight would take 60,000 years to reach the next-closest star system.

After the presentation, NASA's administrator, Michael Griffin, came into the room. I asked him why there had been no discussion of space rocks. He said, "We don't make up our goals. Congress has not instructed us to provide Earth defense. I administer the policy set by Congress and the White House, and that policy calls for a focus on return to the moon. Congress and the White House do not ask me what I think." I asked what NASA's priorities would be if he did set the goals. "The same. Our priorities are correct now," he answered. "We are on the right path. We need to go back to the moon. We don't need a near-Earth-objects program." In a public address about a month later, Griffin said that the moon-base plan was "the finest policy framework for United States civil space activities that I have seen in 40 years."

Actually, Congress has asked NASA to pay more attention to space rocks. In 2005, Congress instructed the agency to mount a sophisticated search of the proximate heavens for asteroids and comets, specifically requesting that NASA locate all near-Earth objects 140 meters or larger that are less than 1.3 astronomical units from the sun-roughly out to the orbit of Mars. Last year, NASA gave Congress its reply: an advanced search of the sort Congress was requesting would cost about $1 billion, and the agency had no intention of diverting funds from existing projects, especially the moon-base initiative.

How did the moon-base idea arise? In 2003, after the shuttle Columbia was lost, manned space operations were temporarily shut down, and the White House spent a year studying possible new missions for NASA. George W. Bush wanted to announce a voyage to Mars. Every Oval Office occupant since John F. Kennedy knows how warmly history has praised him for the success of his pledge to put men on the moon; it's only natural that subsequent presidents would dream about securing their own place in history by sending people to the Red Planet. But the technical barriers and even the most optimistic cost projections for a manned mission to Mars are prohibitive. So in 2004, Bush unveiled a compromise plan: a permanent moon base that would be promoted as a stepping-stone for a Mars mission at some unspecified future date. As anyone with an aerospace engineering background well knows, stopping at the moon, as Bush was suggesting, actually would be an impediment to Mars travel, because huge amounts of fuel would be wasted landing on the moon and then blasting off again. Perhaps something useful to a Mars expedition would be learned in the course of building a moon base; but if the goal is the Red Planet, then spending vast sums on lunar living would only divert that money from the research and development needed for Mars hardware. However, saying that a moon base would one day support a Mars mission allowed Bush to create the impression that his plan would not merely be restaging an effort that had already been completed more than 30 years before. For NASA, a decades-long project to build a moon base would ensure a continuing flow of money to its favorite contractors and to the congressional districts where manned-space-program centers are located. So NASA signed on to the proposal, which Congress approved the following year.

It is instructive, in this context, to consider the agency's rhetoric about China. The Chinese manned space program has been improving and is now about where the U.S. program was in the mid-1960s. Stung by criticism that the moon-base project has no real justification-37 years ago, President Richard Nixon cancelled the final planned Apollo moon missions because the program was accomplishing little at great expense; as early as 1964, the communitarian theorist Amitai Etzioni was calling lunar obsession a "moondoggle"-NASA is selling the new plan as a second moon race, this time against Beijing. "I'll be surprised if the Chinese don't reach the moon before we return," Griffin said. "China is now a strategic peer competitor to the United States in space. China is drawing national prestige from achievements in space, and there will be a tremendous shift in national prestige toward Beijing if the Chinese are operating on the moon and we are not. Great nations have always operated on the frontiers of their era. The moon is the frontier of our era, and we must outperform the Chinese there."

Wouldn't shifting NASA's focus away from wasting money on the moon and toward something of clear benefit for the entire world-identifying and deflecting dangerous space objects-be a surer route to enhancing national prestige? But NASA's institutional instinct is not to ask, "What can we do in space that makes sense?" Rather, it is to ask, "What can we do in space that requires lots of astronauts?" That finding and stopping space rocks would be an expensive mission with little role for the astronaut corps is, in all likelihood, the principal reason NASA doesn't want to talk about the asteroid threat.

NASA's lack of interest in defending against space objects leaves a void the Air Force seems eager to fill. The Air Force has the world's second-largest space program, with a budget of about $11 billion-$6 billion less than NASA's. The tension between the two entities is long-standing. Many in the Air Force believe the service could achieve U.S. space objectives faster and more effectively than NASA. And the Air Force simply wants flyboys in orbit: several times in the past, it has asked Congress to fund its own space station, its own space plane, and its own space-shuttle program. Now, with NASA all but ignoring the space-object threat, the Air Force appears to be seizing an opportunity.

All known space rocks have been discovered using telescopes designed for traditional "soda straw" astronomy-that is, focusing on a small patch of sky. Now the Air Force is funding the first research installation designed to conduct panoramic scans of the sky, a telescope complex called Pan-STARRS, being built by the University of Hawaii. By continuously panning the entire sky, Pan-STARRS should be able to spot many near-Earth objects that so far have gone undetected. The telescope also will have substantially better resolving power and sensitivity than existing survey instruments, enabling it to find small space rocks that have gone undetected because of their faintness.

The Pan-STARRS project has no military utility, so why is the Air Force the sponsor? One speculation is that Pan-STARRS is the Air Force's foot in the door for the Earth-defense mission. If the Air Force won funding to build high-tech devices to fire at asteroids, this would be a major milestone in its goal of an expanded space presence. But space rocks are a natural hazard, not a military threat, and an Air Force Earth-protection initiative, however gallant, would probably cause intense international opposition. Imagine how other governments would react if the Pentagon announced, "Don't worry about those explosions in space-we're protecting you."

Thus, the task of defending Earth from objects falling from the skies seems most fitting for NASA, or perhaps for a multinational civilian agency that might be created. Which raises the question: What could NASA, or anyone else, actually do to provide a defense?

Russell Schweickart, the former Apollo astronaut, runs the B612 Foundation (B612 is the asteroid home of Saint-Exupéry's Little Prince). The foundation's goal is to get NASA officials, Congress, and ultimately the international community to take the space-rock threat seriously; it advocates testing a means of precise asteroid tracking, then trying to change the course of a near-Earth object.

Current telescopes cannot track asteroids or comets accurately enough for researchers to be sure of their courses. When 99942 Apophis was spotted, for example, some calculations suggested it would strike Earth in April 2029, but further study indicates it won't-instead, Apophis should pass between Earth and the moon, during which time it may be visible to the naked eye. The Pan-STARRS telescope complex will greatly improve astronomers' ability to find and track space rocks, and it may be joined by the Large Synoptic Survey Telescope, which would similarly scan the entire sky. Earlier this year, the software billionaires Bill Gates and Charles Simonyi pledged $30 million for work on the LSST, which proponents hope to erect in the mountains of Chile. If it is built, it will be the first major telescope to broadcast its data live over the Web, allowing countless professional and amateur astronomers to look for undiscovered asteroids.

Schweickart thinks, however, that even these instruments will not be able to plot the courses of space rocks with absolute precision. NASA has said that an infrared telescope launched into an orbit near Venus could provide detailed information on the exact courses of space rocks. Such a telescope would look outward from the inner solar system toward Earth, detect the slight warmth of asteroids and comets against the cold background of the cosmos, and track their movements with precision. Congress would need to fund a near-Venus telescope, though, and NASA would need to build it-neither of which is happening.

Another means of gathering data about a potentially threatening near-Earth object would be to launch a space probe toward it and attach a transponder, similar to the transponders used by civilian airliners to report their exact locations and speed; this could give researchers extremely precise information on the object's course. There is no doubt that a probe can rendezvous with a space rock: in 2005, NASA smashed a probe called Deep Impact into the nucleus of comet 9P/Tempel in order to vaporize some of the material on the comet's surface and make a detailed analysis of it. Schweickart estimates that a mission to attach a transponder to an impact-risk asteroid could be staged for about $400 million-far less than the $11.7 billion cost to NASA of the 2003 Columbia disaster.

Then what? In the movies, nuclear bombs are used to destroy space rocks. In NASA's 2007 report to Congress, the agency suggested a similar approach. But nukes are a brute-force solution, and because an international treaty bans nuclear warheads in space, any proposal to use them against an asteroid would require complex diplomatic agreements. Fortunately, it's likely that just causing a slight change in course would avert a strike. The reason is the mechanics of orbits. Many people think of a planet as a vacuum cleaner whose gravity sucks in everything in its vicinity. It's true that a free-falling body will plummet toward the nearest source of gravity-but in space, free-falling bodies are rare. Earth does not plummet into the sun, because the angular momentum of Earth's orbit is in equilibrium with the sun's gravity. And asteroids and comets swirl around the sun with tremendous angular momentum, which prevents them from falling toward most of the bodies they pass, including Earth.

For any space object approaching a planet, there exists a "keyhole"-a patch in space where the planet's gravity and the object's momentum align, causing the asteroid or comet to hurtle toward the planet. Researchers have calculated the keyholes for a few space objects and found that they are tiny, only a few hundred meters across-pinpoints in the immensity of the solar system. You might think of a keyhole as the win-a-free-game opening on the 18th tee of a cheesy, incredibly elaborate miniature-golf course. All around the opening are rotating windmills, giants stomping their feet, dragons walking past, and other obstacles. If your golf ball hits the opening precisely, it will roll down a pipe for a hole in one. Miss by even a bit, and the ball caroms away.

Tiny alterations might be enough to deflect a space rock headed toward a keyhole. "The reason I am optimistic about stopping near-Earth-object impacts is that it looks like we won't need to use fantastic levels of force," Schweickart says. He envisions a "gravitational tractor," a spacecraft weighing only a few tons-enough to have a slight gravitational field. If an asteroid's movements were precisely understood, placing a gravitational tractor in exactly the right place should, ever so slowly, alter the rock's course, because low levels of gravity from the tractor would tug at the asteroid. The rock's course would change only by a minuscule amount, but it would miss the hole-in-one pipe to Earth.

Will the gravitational-tractor idea work? The B612 Foundation recommends testing the technology on an asteroid that has no chance of approaching Earth. If the gravitational tractor should prove impractical or ineffective, other solutions could be considered. Attaching a rocket motor to the side of an asteroid might change its course. So might firing a laser: as materials boiled off the asteroid, the expanding gases would serve as a natural jet engine, pushing it in the opposite direction.

But when it comes to killer comets, you'll just have to lose sleep over the possibility of their approach; there are no proposals for what to do about them. Comets are easy to see when they are near the sun and glowing but are difficult to detect at other times. Many have "eccentric" orbits, spending centuries at tremendous distances from the sun, then falling toward the inner solar system, then slingshotting away again. If you were to add comets to one of those classroom models of the solar system, many would need to come from other floors of the building, or from another school district, in order to be to scale. Advanced telescopes will probably do a good job of detecting most asteroids that pass near Earth, but an unknown comet suddenly headed our way would be a nasty surprise. And because many comets change course when the sun heats their sides and causes their frozen gases to expand, deflecting or destroying them poses technical problems to which there are no ready solutions. The logical first step, then, seems to be to determine how to prevent an asteroid from striking Earth and hope that some future advance, perhaps one building on the asteroid work, proves useful against comets.

None of this will be easy, of course. Unlike in the movies, where impossibly good-looking, wisecracking men and women grab space suits and race to the launchpad immediately after receiving a warning that something is approaching from space, in real life preparations to defend against a space object would take many years. First the necessary hardware must be built-quite possibly a range of space probes and rockets. An asteroid that appeared to pose a serious risk would require extensive study, and a transponder mission could take years to reach it. International debate and consensus would be needed: the possibility of one nation acting alone against a space threat or of, say, competing U.S. and Chinese missions to the same object, is more than a little worrisome. And suppose Asteroid X appeared to threaten Earth. A mission by, say, the United States to deflect or destroy it might fail, or even backfire, by nudging the rock toward a gravitational keyhole rather than away from it. Asteroid X then hits Costa Rica; is the U.S. to blame? In all likelihood, researchers will be unable to estimate where on Earth a space rock will hit. Effectively, then, everyone would be threatened, another reason nations would need to act cooperatively-and achieving international cooperation could be a greater impediment than designing the technology.

We will soon have a new president, and thus an opportunity to reassess NASA's priorities. Whoever takes office will decide whether the nation commits to spending hundreds of billions of dollars on a motel on the moon, or invests in space projects of tangible benefit-space science, environmental studies of Earth, and readying the world for protection against a space-object strike. Although the moon-base initiative has been NASA's focus for four years, almost nothing has yet been built for the project, and comparatively little money has been spent; current plans don't call for substantial funding until the space-shuttle program ends, in 2010. This suggests that NASA could back off from the moon base without having wasted many resources. Further, the new Ares rocket NASA is designing for moon missions might be just the ticket for an asteroid-deflection initiative.

Congress, too, ought to look more sensibly at space priorities. Because it controls federal funding, Congress holds the trump cards. In 2005, it passively approved the moon-base idea, seemingly just as budgetary log-rolling to maintain spending in the congressional districts favored under NASA's current budget hierarchy. The House and Senate ought to demand that the space program have as its first priority returning benefits to taxpayers. It's hard to imagine how taxpayers could benefit from a moon base. It's easy to imagine them benefiting from an effort to protect our world from the ultimate calamity.

"The Sky is Falling"
Gregg Easterbrook
The Atlantic
June 2008, pp 74-84

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