In 2004, astronomers identified Apophis, a 270-meter asteroid heading in our direction. Although NASA initially feared that the odds of Apophis striking Earth in 2029 were 1-in-37, they have since calculated that the asteroid will pass no fewer than 29,450 km above Earth's surface. There is an extremely small chance that Apophis could hit us on a later pass — a 1-in-250,000 in 2036 and a 1-in-330,000 in 2068.

However, Anatoly Perminov, director of the Russian Federal Space Agency, has said that Russia is very concerned about the possibility of a collision with Apophis, and is considering a plan to change the asteroid's course. However, he is a bit vague on his reasons for fearing an impact:

"I don't remember exactly, but it seems to me it could hit the Earth by 2032," Perminov said.

"People's lives are at stake. We should pay several hundred million dollars and build a system that would allow to prevent a collision, rather than sit and wait for it to happen and kill hundreds of thousands of people," Perminov said.

The Space Agency is talking about sending a spacecraft to intercept Apophis, although this won't be an Armageddon scenario. The plan isn't to blow up the asteroid, but to physically push it off course to prevent a close encounter with Earth. Perminov says that, once the project is finalized, NASA, the ESA, and the Chinese space agency will be invited to join the mission.

Russia may send spacecraft to knock away asteroid [Mail via reddit]

Researchers reported this week in Proceedings of the National Academy of Sciences that they found have found shock-synthesized diamonds — known to result from impact events — in the Arlington Canyon on Santa Rosa Island in California, and have previously found similar diamonds in the Greenland Ice Sheet. The placement of the Arlington Canyon diamonds coincide with North America's oldest known human remains — from the Clovis people, who went extinct nearly 13,000 years ago — and the disappearance of the pygmy mammoth from Santa Rosa. This fits with the team's earlier speculation that a comet strike led to a mass mammalian extinction across North America:

In 2007 researchers theorized that a comet set off continental fires that led to the mysterious disappearance of the Clovis people and the extermination of 35 mammal genera, including mammoths, mastodons, ground sloths and camels. The team documented a "black mat" of charcoal throughout North America that contains high levels of iridium, magnetic spheres, and nano-diamonds, which are consistent with such an airburst.

However, the hypothesis remains controversial, and other geologists and archeologists are reluctant to buy the diamonds as evidence of a comet-induced die-off, especially given the absence of an impact crater.

Did a Comet Cause a North American Die-Off around 13,000 Years Ago? [Scientific American]

Anthony Wesley reports that he noticed the spot (seen at the top of the photo above) while observing Jupiter yesterday from his home observatory near Murrumbateman in New South Wales, Australia. Wesley, who had observed the planet two days earlier but had not seen the black spot, speculates that the spot might be an impact spot, possible the result of a comet or asteroid strike.

And, while Phil Plait, Bad Astronomy blogger and author of Death from the Skies!, initially cautioned excited armchair astronomers that the spot might be a mere weather event, he agrees that the emerging data seems to point to an actual impact.

Impact Mark on Jupiter

If you look at the center of the photos, you can see the asteroid moving across the sky. It looks small from Earth, but according to the Associated Press:

The space ball measured between 69 feet and 154 feet in diameter. The Planetary Society said that made it the same size as an asteroid that exploded over Siberia in 1908 and leveled more than 800 square miles of forest.

National Geographic, which posted these photos, reports that the asteroid came within 41,000 miles of Earth on Monday.

SOURCES:

National Geographic

Associated Press

The traditional theory has been that comets and other debris get caught in Jupiter’s gravity well and neutralized by the immense planet. But that theory has come under fire in the past year, and new simulations indicate that Jupiter’s gravitational field could be doing more harm than good:

Using a model of some 40,000 planetesimals, Kevin Grazier of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and his colleagues found that debris in the outer solar system initially had circular orbits and posed no threat to Earth or the other inner planets early in the history of the solar system. But the researchers showed that, through a series of close gravitational encounters with the outer planets, especially Jupiter, the objects assumed more elongated orbits and were handed down to the inner solar system.

In the simulation, Jupiter was responsible for most of the debris that entered in the inner solar system. And, dinosaur-killing comets aside, such debris may have had an impact on the development of our planet:

Not all of the bullets were destructive, Grazier emphasizes. Some of the material that had been delivered to Earth from the outer solar system contained water and other compounds that could have helped life to gain a foothold.

Sniping at Jupiter [via Science Not Fiction]

No one yet has a photo of the fireball that occurred as the asteroid (dubbed 2008 TC3) broke up in the atmosphere, and meteorite fragments will be difficult to find — the impact spot is in northern Sudan near Darfur. But Russian stargazers S. Korotkiy and T. Kryachko, of the Kazan State University Astrotel Observatory, released an animated picture of 2008 TC3's path toward Earth:

Nature reports that NASA was able to give out early warnings of the impact:

On Monday, once Yeomans' office had confirmed the incoming asteroid, he called NASA headquarters in Washington DC, which publicized the impact about seven hours before it occurred. If, however, the incoming object had been 50 to 100 times bigger than it was, the warnings would have been very different. "We would have found out several days sooner," Yeomans says, and arrangements would have been made to get people out of the area of impact.

Alerted of 2008 TC3's proximity and the possibility of seeing a fireball, a Dutch pilot with KLM reported seeing a quick flash in the sky from 1400 kilometers away. An astronomer from Western Ontario even managed to estimate the size of 2008 TC3:

... astronomer Peter Brown of the University of Western Ontario in London, Canada, was able to confirm that the space rock hit the atmosphere at around 02:45 GMT on Tuesday, within minutes of the predicted time and at the predicted location. Brown used data from a Kenya-based array of seven microbarometers, which record atmospheric sound waves to monitor countries' compliance with the Comprehensive Nuclear Test Ban Treaty. The infrasound signals show that the asteroid hit the atmosphere with an energy equivalent to detonating one to two kilotonnes of TNT.

"We can infer from that energy that 2008 TC3 was about three metres in diameter," Brown says.

Though 2008 TC3 was never listed as a potentially hazardous asteroid, its pre-impact discovery and analysis is still an encouraging development for NASA/JPL. Before 2008 TC3 ever entered Earth's atmosphere, astronomers were tracking its progress, and as far as they can tell it burned up just where they said it would. If we can predict the impact of objects this small, it bodes well for our ability to mitigate the imagined disaster scenarios of major impacts.

Great balls of fire [Nature News]
News and information about asteroid impact [Spaceweather.com]

Image from NASA/JPL.

This week, the United Nation's Association of Space Explorers (ASE) held a panel on Asteroid Threat Mitigation to discuss the threat posed by near-Earth objects (NEOs). An asteroid strike would have devastating and lasting consequences:

A hit by even one of the smaller [asteroid] rocks, say the size of a convenience store, would have the impact of 400,000 Hiroshima nuclear bombs exploding at once, he says. The larger varieties (a mile or more in diameter) could hit with as much force as millions of Hiroshima bombs, with devastating planet-wide effects, such as tsunamis, damage to the atmosphere, and radical climate change, with the magnitude of the damage depending on how big it the object is, its composition and if it hits land or water.

Several space programs do currently track NEOs to identify asteroids on a possible collision course with Earth, but these programs are not well coordinated and do not have the funding to track a sufficient number of objects. The ASE plans to deliver a proposal to the UN for a coordinated network of telescopes to better identify and track these asteroids. Although it is not the ASE's role to develop action plans in the event an asteroid threat is detected, its members have contemplated ways to avoid a collision:

In addition to telescopes to detect an incoming rock, that technology could include flying a spacecraft alongside an asteroid that is on course to impact our world. [NEO committee chairman Rusty] Schweickart says the gravitational attraction between the vessel and the space rock would tug on the latter just enough to alter its course and miss Earth. Another, less appealing option would be to shatter or blow up an approaching asteroid.

But is the risk of such an impact real, or is it just movie-engendered hype?

"It's real," says John Pike, director of Globalsecurity.org, an informational Web site focused on security issues, including space. "It's not a question of whether it's going to happen, it's just a question of when it's going to happen."

What 'Deep Impact' might an asteroid make on Earth, astronauts ask and Will an asteroid destroy Earth? Time for UN to keep tabs, say experts [Scientific American]

The theory that life can be carried between planets on rocks ejected by impacts is called lithopanspermia. Some bacteria are able to survive the cold, the dryness and the radiation present in space, especially if they're buried deep inside large asteroids (like Eros, pictured). The shock pressures produced by the impacts that would eject them into space in the first place have always been a stumbling block for lithopanspermists (they love it when you call them that).

A research team made up of German, Russian and U.S. scientists put bacteria thought to have the potential for successful space travel through some rough treatment, using explosives and air guns to slam them around in metal containers. The shock pressures used were similar to the pressures experienced by Martian rocks that were ejected by impacts and eventually reached Earth - we've found about 40 of them so far.

The results: those bacteria are pretty tough. Bacterial endospores and lichens could handle very robust shock pressures, while cyanobacteria were more fragile, but still capable of withstanding impacts strong enough for interplanetary travel. Going from Mars to Earth is a definite possibility. So if the Phoenix Lander finds evidence of past life on Mars, it could mean that all life on Earth is alien. Image by: NASA.

Microbial Rock Inhabitants Survive Hypervelocity Impacts on Mars-Like Host Planets: First Phase of Lithopanspermia Experimentally Tested. [Astrobiology]

We already know that Apophis is due for a close pass by Earth in 2029, and if things go just right (or wrong), April 13, 2036 could be a very bad day for us.

But before we go running for cover, there's a lot we still need to figure out about this mean-looking space rock. From the article:

One problem, says [Jon Giorgini of NASA's Near-Earth Object Program], is that our calculations do not include effects arising from the fact that Earth is not a perfect sphere. This slightly alters its gravitational field and could make a difference to the asteroid's path when it swings close to Earth.

Yet the most powerful steer could come from the way the sunlit asteroid radiates heat, says Giorgini. Radiation gives rise to a small thrust, and since warmer areas of the asteroid radiate more than cooler ones, there is a net force on the asteroid. This phenomenon - the Yarkovsky effect - means our calculations of Apophis's path could be out by millions of kilometres, according to Giorgini, who will present his results at the Asteroid, Comets, and Meteors conference in Baltimore, Maryland, on 17 July.

Of course it's possible that refining the calculations will cause the odds to drop beyond their already minuscule levels. But it's also possible that in a couple of years we are going to be *very* interested in former astronaut Rusty Schweickart's idea of a asteroid-avoidance gravity tractor that just the other week barely scraped up $50,000 of funding.

Source: New Scientist

USA Today, New Scientist, the awesome astronomy blog Bad Astronomy and the BBC and Nature and just about every sciency news outlet all have items devoted to the centennial. But they disagree on what the Tunguska Event was. USA Today calls it an "impact,' but Bad Astronomy says "air blast" and says there's no evidence anything hit the ground. New Scientist has posted a video in which their reporter circles Lake Cheko nearby the blast site in a helicopter and speculates whether it's the smoking gun of an impact.

What's going on here? Tunguska is probably the most heavily studied impact/air blast/space rock encounter on Earth and we know almost nothing about how it happened. It's also hard to say how likely it is that it will happen again, though one scientist's guess isn't comforting:

In terms of risk to Earth, astronomer David Morrison of NASA's Ames Research Center says a Tunguska-magnitude strike could happen once every two centuries and a bigger impact, a "civilization-threatening" million-megaton strike, could happen once every 2 million years. Even though astronomers have spotted more of these nearby asteroids in the last two decades, the estimated odds of an impact have actually declined, as Morrison notes in a May issue of NEO News, his asteroid newsletter.

If Morrison's right, we've got at best another century to learn as much as we can from Tunguska before another similar event hits home — maybe less. And in the mean time, we'll have plenty of close calls reminding us that we are basically sitting ducks unless we start doing something about one of the greatest threats to our survival as a civilization.

Scientists have known for years about the Borealis Basin — a region of lowlands that take up the northern half of Mars. Some thought a volcanic cataclysm caused the crater, while other speculated it could have been an impact. With the help of detailed geological readings from the Mars Reconnaissance Orbiter and Global Surveyor, they've been able to solve the mystery, concluding that something struck Mars with the force of 1 million billion Nagasaki-sized atomic bombs on a bad day four billion years ago.

Nature has devoted a special issue called "Cosmic Impacts" centered on the new findings, with a cool story on the 100th Anniversary of the Tunguska Event and a sweet photo gallery of the solar system's prettiest craters that are worth a look.

Source: Nature via BBC

While Griff and his Bush Administration cronies dust off their tie-dye shirts, smoke a bowl and try to relive NASA's Apollo golden years with their mission back to the Moon, it's good to know someone's paying attention to the Asteroid threat.

Of the many different methods proposed for altering space rocks' course — or blowing them up — gravity tractoring seems to be the most attractive. By launching a satellite towards a Near-Earth Asteroid (NEA) and hanging out close by, the vehicle's gravitational influence will slowly, and ever so slightly alter the asteroid's course. The process requires a lot of advaned notice, but should work without the use of lasers, nuclear weapons, or Bruce Willis.

From B612's mission statement:

The reality of concern to us, among others, is that the discovery of a NEA headed toward an impact with Earth could be announced at any time by the Spaceguard program. If this were to happen the public would be extremely concerned and demand to know what is being done about it.

Unfortunately the answer is "nothing". This, it seems to us, is intolerable and could cause widespread alarm. For this reason the B612 Foundation, recognizing that national governments feel (to the extent that they have considered the matter) that they are not in a position to spend public money on mitigation, are taking the initiative now to begin this process with the use of private funds. We believe that there are adequate numbers of intelligent and concerned people to support the critical initial planning work that needs to be done to eventually reach an operational system to deflect incoming NEAs.

Our conviction is that there is nothing more powerful to convince the public that this audacious challenge can be met than to actually do it. Our goal is to physically deflect a representative asteroid as a demonstration that a longer term, more challenging operational system can become a reality.

Now of course it's a possibility that B612 could take a rock that's not an imminent threat to Earth and make it one by altering its course, but that's pretty unlikely. More important is that someone is serious about saving humanity from a space rock strike, but they're seriously underfunded — $50,000 is a drop in the bucket, and we're going to need an X-Prize style contest, or some mega-rich asteroid geek to pony up some bucks if we're ever going to dodge the big one.

Source: LiveScience

Image: B612 Foundation

NASA's list of potentially hazardous asteroids (PHAs) currently numbers 959. That's 1,000 asteroids that astronomers pretty much know are going to get closer than 7.5 million kilomters to Earth, about 20 times the distance from here to the Moon. Five of those are expected to come between Earth and the Moon over the next century.

So we'll have a few close shaves but nothing to worry about, right? Not so fast. The total number of PHAs and comets astronomers think are out there is probably more like 20,000. That means we've mapped about 5% of the objects that stand a good chance of hitting us. So take the future part of this chart as a best-case scenario. The past five close encounters, however, show just how vulnerable we are:

1) The Comet of 1491. This one must've scared the hell out of some folks. At a little less than four times the distance to the moon, this was the closest pass ever recorded at the time, and no one knows for sure how big it was. Little did our ancestors know how much more interesting things would get.

2) Tunguska, 1908. One of the most famous Earth lcose calls of all time, it was also a pipsqueak. For a long time scientists believed a comet perhaps 60 meters in diameter exploded over Siberia with a force of as much at 30 megatons, or about 2,000 times more powerful than the atomic bomb dropped on Hiroshima, though nothing solid ever hit the planet. All those pictures of flattened forest certianly look impressive, but last year, scientists re-crunched the numbers and found that the comet oculd've been as small as 30 meters, and the blast just 5 megatons. In other words, much smaller objects can do way more damage than we ever thought before. Gulp.

3) The Great Daylight Fireball of 1972. The name says it all — it doesn't get much closer than this. Size estimates range from 3 to 14 meters in diameter, depending on whether it was ice or rock. Whatever it was, the object called US19720810 burned through the atmosphere from Utah to Canda for about a minute and a half. Luckily, the space rock struck a glancing blow — had it hit Earth directly, it could've blasted us with 1/2 a Hiroshima worth of energy.

4) 2004 FH and 2004 FU162. At 30 meters in diameter and made of solid rock, 2004 FH would be a thumper of Tunguska proportions if it ever hit home. In the right (or wrong) place, it could detroy a city. As it was, it passed 43,000 kilometers above Earth on on March 18, 2004.

Three weeks later, FU 162 came whizzing along. Astronomers basically discovered it at bascially the same time as the 6-meter in diameter rock soared just 6,400 kilometers above Earth's surface.

5) Comet Hyakutake. Now we're getting into civilization-threatening territory. At 2 kilometers in diameters, this comet only got within about 40 lunar distances to Earth in 1996. Compared ot our other close calls, that's pretty comfortable, but considr this: it was discovered less than two months before its closest pass. Had it been on a collision course with Earth there's almost nothing we could've done other than brace for the millions dead, massive climate disruption, crop failure, 500-foot high tsunami...you get the idea.

FUTURE:

6) 1999 AN10. In a little less than 20 years, our usually quiet Earth-Moon system is going to have a lot of visitors. In August 2027, AN 10 is going to get about one lunar distance from Earth, and we'll get a chance to see just how big this bad boy is. Estimates range from 1/2 to 2 kilometers in diameter, plenty large to leave a dent in humanity if it ever gets closer.

7) 2001 WN5. Just six months after AN10 comes a callin' WN5 will get even closer, just about splitting the difference between Earth and the Moon. At 700 meters in diamters, this asteroid has a got potential for major dmaage, but current odds of impact are rated a negligible.

8) 99942 Apophis. By far the most famous of the end-bringing objects we know about in our solar system, astronomers thought for a while that this 270 meter-wide rock had an almost 3% chance of hitting us. Since then, odds have been lowered to 1 in 43,000 that it could slam into Earth in 2029. But if it passes through a gravitaitonal keyhole — a tiny region in space that could tweak its orbit ever so slightly — an impact could still happen on April 13, 2036.

9) 2005 WY55. Just 200 meters wide, astronomers think this asteroid could still pack a wallop. Right now it's scheduled to get within about 75,000 km of Earth, but impact odds are big enough to kep in mind — currently they're rated at around 1 in 70,000. If our number comes up on that faeful dayin May 2065, look out — blast yield estimates from this rock range to 1100 megatons.

10) 2000 WO107. Depending on how well humanity holds up under climate change, bird flu, and all the other things that could potentially kill us off, we might be able to look up and see WO107 zoom by in December 2140. The 400 meter-wide rock isn't scheduled to hit us — it should get about half way between Earth and the Moon — but if calculations are off by even a little bit (and all of the future examples here have some uncertainty) we could care a lot.

Sources: NASA's Near Earth Object Program, Harvard List of PHAs

Additional research by Nivair H. Gabriel. Image by Stephanie Fox.

Previous experiments have shown that microbes can survive in the punishing cold of space. Their ability to hide out in a rock's interior, safe from a vacuum is well-documented too.

But scientists haven't been able to tell whether hearty critters could survive the heat and crushing force of an asteroid impact that would be needed to eject them into space in the first place. Astrobiologists at the Institute of Aerospace Medicine in Germany have finally connected all the dots with a new experiment in the Spring issue of Astrobiology Magazine

And what better way to simulate an asteroid impact than to smash rocks together? That's exactly what the scientists involved in this research did, after sprinkling test rocks with bacteria known live inside stone, some cyanobacteria, and a dash of lichen onto them. All three lifeforms survived the high-speed collision, suggesting they could be floating through outer space even now, waiting for a chance encounter with distant planet to plant the seeds of a whole new 'alien' biosphere.

Source: Astrobiology Magazine

Image: NASA

If a comet or asteroid doesn't slam into the planet between now and then, ending civilization, it will greatly improve our chances of killing ourselves off, instead of being snuffed out by some cosmic accident. Thank you, Canucks.

As this New Scientist article says, astronomers on the ground have been looking for potentially threatening asteroids for decades, but even a small space telescope like NEOSSat will really help us out:

Scientists are using ground-based telescopes to track down more of the near-Earth objects (NEOs) to determine if any could potentially hit the planet in the foreseeable future. But some of these objects are difficult to see from the ground.

t will rely on a telescope with a 15-centimetre mirror, smaller than many backyard telescopes used by amateur astronomers. Chief scientists for the mission are Alan Hildebrand of the University of Calgary and Brad Wallace of Defence Research and Development Canada.

Despite its modest dimensions, the spacecraft's unique vantage point in space may allow it to spot objects that are difficult to see from the ground.

Most of the NEOs found so far have elongated orbits that extend far away from the Sun. But some never venture much beyond Earth's orbit.

These stay close to the Sun in the sky, meaning they must be observed when the Sun is not far below the horizon - before sunrise and after sunset. At those times, the glow of the sky can make the objects hard to see.

Operating above the atmosphere, NEOSSat will have a clearer view of such objects. It is expected to catalogue at least 50% of the ones that span more than 1 kilometre.

These close-in objects are more dangerous than their more far-flung siblings because they spend more time in the vicinity of Earth, where there is the potential for a collision, says Timothy Spahr. An astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, US, Spahr co-authored a 2007 NASA report to the US Congress on the risk to Earth from NEOs.

NEOSSat only weighs about 60kg and cost $10 million to build...about what it costs for a candy bar in the Pentagon cafeteria. And for that pittance all we get is an unprecedented level of interplanetary defense. We owe you one, Canada.

Source: New Scientist (image: TreeHugger)