Updated 'Deep Impact' January 25

Avoiding Planetary Hits Is A Big Job

Jan 25, 2010

A new report from the National Research Council lays out options NASA could follow to detect more near-Earth objects (NEOs) - asteroids and comets that could pose a hazard if they cross Earth's orbit. The report says the $4 million the U.S. spends annually to search for NEOs is insufficient to meet a congressionally mandated requirement to detect NEOs that could threaten Earth.
Congress mandated in 2005 that NASA discover 90 percent of NEOs whose diameter is 140 meters or greater by 2020, and asked the National Research Council in 2008 to form a committee to determine the optimum approach to doing so. In an interim report released last year, the committee concluded that it was impossible for NASA to meet that goal, since Congress has not appropriated new funds for the survey nor has the administration asked for them.

In its final report, the committee lays out two approaches that would allow NASA to complete its goal soon after the 2020 deadline; the approach chosen would depend on the priority policymakers attach to spotting NEOs.

If finishing NASA's survey as close as possible to the original 2020 deadline is considered most important, a mission using a space-based telescope conducted in concert with observations from a suitable ground-based telescope is the best approach, the report says. If conserving costs is deemed most important, the use of a ground-based telescope only is preferable.

The report also recommends that NASA monitor for smaller objects - those down to 30 to 50 meters in diameter - which recent research suggests can be highly destructive. However, the report stresses that searching for smaller objects should not interfere with first fulfilling the mandate from Congress. Beyond completion of that mandate, the report notes the need for constant vigilance in monitoring the skies, so as to detect all dangerous NEOs.

In addition, the nation should undertake a peer-reviewed research program to better investigate the many unknown aspects connected with detecting NEOs and countering those that could be a threat. The U.S. should also take the lead in organizing an international entity to develop a detailed plan for dealing with hazards from these objects.

In addition, the report recommends that immediate action be taken to ensure the continued operation of the Arecibo Observatory in Puerto Rico. NASA and NSF should support a vigorous program of NEO observations at Arecibo, and NASA should also support such a program at the Goldstone Deep Space Communications Complex.

Although these facilities cannot discover NEOs, they play an important role in accurately determining the orbits and characterizing the properties of NEOs within radar range.

The Scope of the Hazard
Near-Earth objects are asteroids and comets that orbit the Sun and approach or cross Earth's orbit. An asteroid or comet about 10 kilometers in diameter struck the Yucatan peninsula 65 million years ago and caused global devastation, probably wiping out large numbers of plant and animal species including the dinosaurs. Objects as large as this one strike Earth only about once every 100 million years on average, the report notes.

NASA has been highly successful at detecting and tracking objects 1 kilometer in diameter or larger, and continues to search for these large objects. Objects down to sizes of about 140 meters in diameter - which NASA has been mandated to survey for - would cause regional damage; such impacts happen on average every 30,000 years, the report says.

While impacts by large NEOs are rare, a single impact could inflict extreme damage, raising the classic problem of how to confront a possibility that is both very rare and very important. Far more likely are those impacts that cause only moderate damage and few fatalities.

Conducting surveys for NEOs and detailed studies of ways to mitigate collisions is best viewed as a form of insurance, the report says. How much to spend on these insurance premiums is a decision that must be made by the nation's policymakers.

Mitigating Damage
The report also examines what is known about methods to defend against NEOs. These methods are new and still immature. No single approach is effective for the full range of near-Earth objects, the committee concluded. But with sufficient warning, a suite of four types of mitigation is adequate to meet the threat from all NEOs, except the most energetic ones.

+ Civil defense (evacuation, sheltering in place, providing emergency infrastructure) is a cost-effective mitigation measure for saving lives from the smallest NEO impact events and is a necessary part of mitigation for larger events.

+ "Slow push" or "slow pull" methods use a spacecraft to exert force on the target object to gradually change its orbit to avoid collision with the Earth. This technique is practical only for small NEOs (tens of meters to roughly 100 meters in diameter) or possibly for medium-sized objects (hundreds of meters), but would likely require decades of warning. Of the slow push/pull techniques, the gravity tractor appears to be by far the closest to technological readiness.

+ Kinetic methods, which fly a spacecraft into the NEO to change its orbit, could defend against moderately sized objects (many hundreds of meters to 1 kilometer in diameter), but also may require decades of warning time.

+ Nuclear explosions are the only current, practical means for dealing with large NEOs (diameters greater than 1 kilometer) or as a backup for smaller ones if other methods were to fail.

Although all of these methods are conceptually valid, none is now ready to implement on short notice, the report says. Civil defense and kinetic impactors are probably the closest to readiness, but even these require additional study prior to reliance on them.

Given the significant unknowns about many aspects of the threat and its mitigation, the report recommends that the U.S. start a peer-reviewed, targeted research program on the hazards posed by NEOs, and how to deal with them. Because this is a policy-driven, applied research program, it should not be in competition with basic scientific research programs or be funded from them, the report adds.

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February 2, 2010 10:00 AM (EST)
News Release Number: STScI-2010-07
Suspected Asteroid Collision Leaves Odd X-Pattern of Trailing Debris

Something awfully curious is happening 100 million miles from Earth in the asteroid belt. There's a newly discovered object that superficially looks like a comet but lives among the asteroids. The distinction? Comets swoop along elliptical orbits close in to the Sun and grow long gaseous and dusty tails, as ices near the surface turn into vapor and release dust. But asteroids are mostly in circular orbits in the asteroid belt and are not normally expected to be "volatile."

The mystery object was discovered on January 6, 2010, by the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey. The object appears so unusual in ground-based telescopic images that discretionary time on NASA's Hubble Space Telescope was used to take a close-up look. The observations show a bizarre X-pattern of filamentary structures near the point-like nucleus of the object and trailing streamers of dust. This complex structure suggests the object is not a comet but instead the product of a head-on collision between two asteroids traveling five times faster than a rifle bullet. Astronomers have long thought that the asteroid belt is being ground down through collisions, but such a smashup has never before been seen.

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February 3, 2010, 21:20
Fireball seen over Ireland

PADDY CLANCY

Members of the public throughout the country have been reporting sightings of a fireball in the skies this evening.

Tommy Moore from Astronomy Ireland said a space rock collided with the earth’s atmosphere at about 6pm, showering debris over many parts of the country.

Mr Moore said: “A major explosion happened in the sky over Ireland. We think it’s a fireball, that’s a rock from space the earth has slammed into and they burn up as huge shooting stars. This one appears to have lit up the whole country. The phones here in Astronomy Ireland are going crazy.”

One man told his local radio station: “I saw the ball of fire just above the trees. I rang the emergency services. I thought it was a helicopter.” Another said: “I thought it was a bright gas cylinder. It seemed to get brighter as it was approaching the ground.”

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Meteorite Hits Mexico Leaving 30 Meter Crater in Ahuazotepec Municipality
Thursday, February 11, 2010
By Newsolio Editor

A meteorite has smashed into the ground in Mexico, leaving a 30 meter (100 feet) wide crater, reports said.

The meteorite impact was in the Ahuazotepec Municipality in Central Mexico between the cities of Puebla and Hidalgo.

The precise impact area of the meteorite was in a relatively unpopulated area and hit around 6.30pm local time, Mexican media said.

The Ahuazotepec, Mexico meteorite impact was so massive it broke windows in homes many kilometers from the epicenter and people reported buildings swaying and mass confusion. Other reports said the Mexico meteorite impact partially damaged a road and a bridge.

The Mexican military was called in to lock down the area where the apparent space rock slammed into the ground.

Initial fears where that the impact was a aircraft crashing to the ground, but that report was later dismissed.

The Central Mexico meteorite event was witnessed by countless people in the region of the impact, with people as far away as Mexico City saying they saw the burning object enter the atmosphere.

Update: The Mexican government now believes the space junk was not a meteorite, but perhaps a Russian satellite.

Do you have the link Dreemz? I want to add this to the timeline for the upcoming Phipoint Deep Impact

Science.

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'Dream Team' Agrees Huge Asteroid Killed Dinosaurs
Updated: 1 hour 14 minutes ago

Traci Watson Contributor
AOL News
(March 4) -- For decades, scientists have debated exactly what kind of cataclysm was responsible for the extinction of the dinosaurs. Did a giant rock from outer space blast T. rex and his ilk off the face of the Earth? Or was a huge volcanic eruption to blame?

Now the jury is in -- maybe. In Friday's issue of the prestigious journal Science, a "dream team" of 41 researchers from 12 nations declares that the evidence points overwhelmingly to a mountain-sized asteroid that walloped the planet 65 million years ago. The monstrous boulder left an equally monstrous scar, a 120-mile-wide dimple known as the Chicxulub crater on the Mexican coast.

"We assessed the whole picture," says Kirk Johnson of the Denver Museum of Nature and Science. "The answer is quite simple. ... The Chicxulub crater really is the culprit."
An allosaurus skeleton at the Carnegie Museum of Natural History in Pittsburgh, Pa.
Andrew Rush, AP
What killed off Earth's dinosaurs and many other life forms 65 million years ago? An international research team has concluded it was an asteroid that hit Mexico.

The holdouts who downplay the asteroid's role are unconvinced.

"It's the same old story from them," says Norman MacLeod of the Natural History Museum in London, referring to the team that wrote the new paper. "The authors conveniently forget to mention critical data."

But MacLeod and another prominent doubter, Gerta Keller of Princeton University, don't dispute that a colossal space rock hit the Earth roughly 65 million years ago. And whether or not that led to the demise of the dinosaurs, new research is painting an increasingly detailed picture of the hellish conditions after the asteroid's arrival.

It would take a mighty rock to do in the mighty lizards known as dinosaurs, and on that count the Chicxulub asteroid fits the bill. It was big -- more than seven miles across, three times the width of Manhattan -- and it was moving fast -- 20 times the speed of a rifle bullet. When it hit, the explosion unleashed a billion times more energy than the atomic bomb dropped on Hiroshima, says Gareth Collins of Imperial College London.

In a paper published last year, Collins found that the asteroid in 30 seconds drilled an initial crater 19 miles deep, nearly penetrating the Earth's crust. Earthquakes of up to magnitude 11 -- 1,000 times more powerful than the recent Chilean earthquake -- shook the area, and tsunamis more than 300 feet high inundated nearby coasts.

Collins has created Google Maps-based scenarios of what happened.
A high resolution topographic map of the Yucatan Peninsula and Chicxulub impact crater.
NASA/Getty Images
A faint arc of dark green in the upper left portion of this map shows shows what's left of the Chicxulub crater on Mexico's Yucatan Peninsula. The asteroid that created the crater was more than seven miles wide and moved 20 times faster than a rifle bullet.

The impact was so violent that it melted and vaporized both the asteroid itself and the spot the asteroid hit. Within an hour, melted rock had splattered as far as northern Canada, says David Kring of the Lunar and Planetary Institute. An immense plume of vaporized and melted material burst through the atmosphere and into outer space. Within a few hours, tiny drops from that plume began raining down through the atmosphere all across the Earth's surface.

As they fell, these drops grew hotter, literally broiling the planet for several minutes, according to another 2009 study. Any exposed animal "is not going to do so well," says the University of Vienna's Tamara Goldin, one of the study's authors.

The combination of dust, soot and caustic chemicals filling the air blotted out the sun, Kring says. The sky close to the crater first glowed red then went pitch black. All over the globe, a biblical darkness fell, lasting perhaps a week, maybe nearly a year.

The darkness shut down photosynthesis, the process by which plants capture sunlight to grow. Huge swathes of forest died. Entire classes of animals perished.

But that's where the narrative gets disputed. The authors of the new study say that more than 60 percent of species went extinct, including most dinosaurs. MacLeod, though, says that dinosaurs were in decline for millions of years before the asteroid hit. He also wonders why, if the asteroid strike was such a doomsday event, some classes of species survived and even thrived.

Keller questions even more basic claims, such as the dating of the asteroid strike. She argues that the Chicxulub rock hammered Earth hundreds of thousands of years before the mass extinctions shown in the fossil record.

Just such arguments -- and media coverage of them -- are what prompted the scientists to publish their new paper, Goldin says. After ignoring Keller and other skeptics for many years, the pro-crater forces got so frustrated that they decided to put all the evidence together.

"It is almost impossible to change the skeptics' minds," Goldin concedes. "But we hope we can communicate to the scientific community and the public that this impact-induced environmental catastrophe did happen."
Filed under: Nation, World, Science

Comet trail may have caused last ice age

Apr 02, 2010

A thousand-year freeze that began in 11,000 B.C. may have been caused by thousands of atomic-force chunks from a disintegrating comet, a British scientist said.
The fragments, each hitting with the force of a 1-megaton nuclear bomb, triggered fires that covered whole continents and filled the atmosphere with smoke and soot that blotted out the sun, said Bill Napier, a professor at Cardiff University Astrobiology Center.

Napier said Earth may have strayed into a dense trail of fragments being shed by a large comet.

The resulting freeze caused glaciers to advance, disrupted human cultures and wiped out an estimated 35 families of North American mammals, The Daily Telegraph reported Friday.

There is "compelling evidence" the main comet has been breaking apart ever since, leading to meteor streams known as the Taurid Complex, Napier wrote in the journal Monthly Notices of the Royal Astronomical Society.

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Asteroid to Fly by Within Moon's Orbit Thursday

April 06, 2010

A newly discovered asteroid, 2010 GA6, will safely fly by Earth this Thursday at 4:06 p.m. Pacific (23:06 U.T.C.). At time of closest approach 2010 GA6 will be about 359,000 kilometers (223,000 miles) away from Earth - about 9/10ths the distance from to the moon. The asteroid, approximately 22 meters (71 feet) wide, was discovered by the Catalina Sky Survey, Tucson, Az.

"Fly bys of near-Earth objects within the moon's orbit occur every few weeks," said Don Yeomans of NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif.

NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.

JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. Cornell University, Ithaca, N.Y., operates the Arecibo Observatory under a cooperative agreement with the National Science Foundation in Arlington, Va.

For more information about asteroids and near-Earth objects, visit:

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Obama's asteroid goal is riskier than moon
‘It is really the hardest thing we can do,’ says NASA administrator

April 16, 2010

CAPE CANAVERAL, Fla. - Landing a man on the moon was a towering achievement. Now the president has given NASA an even harder job, one with a certain Hollywood quality: sending astronauts to an asteroid, a giant speeding rock, just 15 years from now.

Space experts say such a voyage could take several months longer than a journey to the moon and entail far greater dangers.

"It is really the hardest thing we can do," NASA Administrator Charles Bolden said.


Going to an asteroid could provide vital training for an eventual mission to Mars. It might help unlock the secrets of how our solar system formed. And it could give mankind the know-how to do something that has been accomplished only in the movies by a few square-jawed, squinty-eyed heroes: saving the Earth from a collision with a killer asteroid.

"You could be saving humankind. That's worthy, isn't it?" said Bill Nye, TV's Science Guy and vice president of the Planetary Society.

President Barack Obama outlined NASA's new path during a visit to the Kennedy Space Center on Thursday.

"By 2025, we expect new spacecraft designed for long journeys to allow us to begin the first-ever crewed missions beyond the moon into deep space," he said. "We'll start by sending astronauts to an asteroid for the first time in history."

On the day the president announced the goal, a NASA task force of scientists, engineers and ex-astronauts was meeting in Boston to work on a plan to protect Earth from a cataclysmic collision with an asteroid or a comet.

NASA has tracked nearly 7,000 near-Earth objects that are bigger than several feet across. Of those, 1,111 ( emphasis Dutch)are "potentially hazardous asteroids." Objects bigger than two-thirds of a mile are major killers and hit Earth every several hundred thousand years. Scientists believe it was a 6-mile-wide asteroid that wiped out the dinosaurs 65 million years ago.

Landing on an asteroid and giving it a well-timed nudge "would demonstrate once and for all that we're smarter than the dinosaurs and can avoid what they didn't," said White House science adviser John Holdren.

Experts don't have a particular asteroid in mind for the deep-space voyage, but there are a few dozen top candidates, most of which pass within about 5 million miles of Earth. That is 20 times more distant than the moon, which is about 239,000 miles from Earth on average.

Most of the top asteroid candidates are less than a quarter-mile across. The moon is about 2,160 miles in diameter.

Going to an asteroid could provide clues about the solar system's formation, because asteroids are essentially fossils from 4.6 billion years ago, when planets first formed, said Don Yeomans, manager of NASA's Near Earth Object program at the Jet Propulsion Lab.

And an asteroid mission would be a Mars training ground, given the distance and alien locale.

"If humans can't make it to near-Earth objects, they can't make it to Mars," said MIT astronautics professor Ed Crawley.

Also, asteroids contain such substances as hydrogen, carbon, iron and platinum, which could be used by astronauts to make fuel and equipment — skills that would also be necessary on a visit to Mars.

While Apollo 11 took eight days to go to the moon and back in 1969, a typical round-trip mission to a near-Earth asteroid would last about 200 days, Crawley said. That would demand new propulsion and life-support technology. And it would be riskier. Aborting a mission in an emergency would still leave people stuck in space for several weeks.

The space agency may need to develop special living quarters, radiation shields or other new technology to allow astronauts to live in deep space so long, said NASA chief technology officer Bobby Braun.

Even though an asteroid would be farther than the moon, the voyage would use less fuel and be cheaper because an asteroid has no gravity. The rocket that carries the astronauts home would not have to expend fuel to escape the asteroid's pull.

On the other hand, because of the lack of gravity, a spaceship could not safely land on an asteroid; it would bounce off the surface. Instead, it would have to hover next to the asteroid, and the astronauts would have to spacewalk down to the ground, Yeomans said.

Once there, they would need some combination of jet packs, spikes or nets to enable them to walk without skittering off the asteroid and floating away, he said.

"You would need some way to hold yourself down," Yeomans said. "You'd launch yourself into space every time you took a step."

Just being there could be extremely disorienting, said planetary scientist Tom Jones, co-chairman of the NASA task force on protecting Earth from dangerous objects. The rock would be so small that the sun would spin across the sky and the horizon would only be a few yards long. At 5 million miles away, the Earth would look like a mere BB in the sky.

"It's going to be a strange alien environment being on an asteroid," Jones said.

But Jones, a former astronaut, said that wouldn't stop astronauts from angling to be a part of such a mission: "You'll have plenty of people excited about exploring an ancient and alien world."

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Junkyard Circling the Earth Is Growing, Scientists Say

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Tamara Lytle

Tamara Lytle Contributor
AOL News
(April TK?) -- Imagine half a million marbles circling Earth -- a sort of celestial obstacle course for the International Space Station, shuttles and satellites.

That's the increasingly problematic issue of orbital debris. The objects can be as big as a defunct satellite, but -- traveling at speeds of 17,500 miles an hour or more -- even a paint flake can put a chink in a space shuttle window, as happened on one mission.

"It's almost like it's being sandblasted by these very small pieces of space debris," said Roderick Heelis, director of the Hanson Center for Space Sciences at the University of Texas at Dallas.
This is a computer generated image provided by the European Space Agency which shows an artist impression of
ESA / AP
A computer-generated image shows "space junk" around the Earth. "Space is like the Wild West used to be," said David Wright, senior scientist at the Union of Concerned Scientists.

The amount of junk in low Earth orbit -- where the shuttle and the space station travel -- has increased 60 percent since 2006, according to NASA. Recent additions to the trash belt include 3,000 pieces of debris created last year when China destroyed a defunct satellite as a test of anti-satellite military capability, and 2,000 more bits that came from a collision this February between an Iridium commercial satellite and a dead Russian satellite.

William Jeffs, NASA spokesman for the Astromaterials Research and Exploration Science Directorate at the Johnson Space Center in Houston, said the millions of pieces of space junk include half a million pieces bigger than a marble and 20,000 bigger than a softball.

Although the shuttle will be retired later this year and the space station program will end in 2020, the problem will continue to pose a threat to satellites vital for communications, weather monitoring and the military. So it's little surprise the United States and other countries have begun to focus more on the issue of space junk, designing satellites that deorbit themselves after they finish their jobs and other techniques to reduce debris.

As for the space station itself, its trash is loaded into the Russian Progress vehicles, which ferry supplies up. After the Progress is filled with junk -- something NASA spokesman Kelly Humphries likened to "cramming your suitcase full of everything you want to take with you" -- it is sent hurtling toward Earth, where much of it burns up in the atmosphere.

Some of the trash that doesn't fit into the Progress, along with experiments and broken items NASA wants to inspect, comes back on the Leonardo Multi-Purpose Logistics Module in Discovery's payload bay. When Discovery returns to Earth on Sunday, it will be carting 20,000 pounds of trash and equipment.

It's all a sea change from the days when Russia's Mir space station dumped its trash into space -- 87 bags of it, said Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. (That trash likely is long gone, since it was in low Earth orbit moving at a slow enough speed for Earth's gravitational pull to quickly bring it down to a fiery death.)

"Space is like the Wild West used to be," said David Wright, senior scientist at the Union of Concerned Scientists. The first explorers of the new frontier "didn't feel like they needed laws. They dumped their trash anywhere."

Now, new binding international agreements are needed to bar anti-satellite tests like the one China did and require that countries that launch satellites and other spacecraft be more careful about what gets left behind in space, Wright said. Otherwise, "all the great things you want to use space for beneficially could be much, much more difficult to use."

Meanwhile, the United States and other countries have an extensive system for tracking space debris, using telescopes and computer modeling. Bob Plemmons, professor of mathematics and computer science at Wake Forest University, does some of the tracking for the Air Force. The problem is getting worse as more and more countries put up satellites, he noted: "With technology today, it's essential to have good communications satellites."

And the end of the space shuttle program will mean some data collected on weather conditions and the positions of other satellites will need to be collected by new satellites, adding to the risk, he said.

In higher orbits, such as those for satellites, the debris is going even faster, Heelis pointed out. And it's farther from Earth, so it takes longer to be destroyed -- decades or centuries instead of years.

"Space is large, so the chances of [debris] hitting you are very small," Heelis said. "But if it does hit you, the consequences are very large."
Filed under: Nation, World, Science, Tech

Scientists Finds Evidence Of Water Ice On Asteroid's Surface

Apr 29, 2010
Asteroids may not be the dark, dry, lifeless chunks of rock scientists have long thought.
Josh Emery, research assistant professor with the earth and planetary sciences department at the University of Tennessee, Knoxville, has found evidence of water ice and organic material on the asteroid 24 Themis. This evidence supports the idea that asteroids could be responsible for bringing water and organic material to Earth.

The findings are detailed in the journal "Nature."

Using NASA's Infrared Telescope Facility on Hawaii's Mauna Kea, Emery and Andrew Rivkin of Johns Hopkins University in Laurel, Md., examined the surface of 24 Themis, a 200-kilometer wide asteroid that sits halfway between Mars and Jupiter.

By measuring the spectrum of infrared sunlight reflected by the object, the researchers found the spectrum consistent with frozen water and determined that 24 Themis is coated with a thin film of ice. They also detected organic material.

"The organics we detected appear to be complex, long-chained molecules. Raining down on a barren Earth in meteorites, these could have given a big kick-start to the development of life," Emery said.

Emery noted that finding ice on the surface of 24 Themis was a surprise because the surface is too warm for ice to stick around for a long time.

"This implies that ice is quite abundant in the interior of 24 Themis and perhaps many other asteroids. This ice on asteroids may be the answer to the puzzle of where Earth's water came from," he said.

Still, how the water ice got there is unclear.

24 Themis' proximity to the sun causes ice to vaporize. However, the researchers' findings suggest the asteroid's lifetime of ice ranges from thousands to millions of years depending on the latitude.

Therefore, the ice is regularly being replenished. The scientists theorize this is done by a process of "outgassing" in which ice buried within the asteroid escapes slowly as vapor migrates through cracks to the surface or as vapor escapes quickly and sporadically when 24 Themis is hit by space debris.

Since Themis is part of an asteroid "family" that was formed from a large impact and the subsequent fragmentation of a larger body long ago, this scenario means the parent body also had ice and has deep implications for how our solar system formed.

The discovery of abundant ice on 24 Themis demonstrates that water is much more common in the Main Belt of asteroids than previously thought.

"Asteroids have generally been viewed as being very dry. It now appears that when the asteroids and planets were first forming in the very early Solar System, ice extended far into the Main Belt region," Emery said.

"Extending this refined view to planetary systems around other stars, the building blocks of life - water and organics - may be more common near each star's habitable zone. The coming years will be truly exciting as astronomers search to discover whether these building blocks of life have worked their magic there as well."

The scientists' discovery also further blurs the line between comets and asteroids. Asteroids have long been considered to be rocky and comets icy. Furthermore, it was once believed that comets could have brought water to Earth. This theory was nixed when it was discovered comets' water has different isotopic signatures than water on Earth.

Now, due to Emery and Rivkin's findings, many wonder if asteroids could be responsible for seeding Earth with the ingredients for life.

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Australian scientists find Timor Sea meteorite crater


Australian scientists have discovered a crater deep beneath the Timor Sea made during a heavy meteor storm which may have altered the Earth’s climate, the lead researcher said yesterday.

Australian National University archaeologist Andrew Glikson said seismic activity led experts to the Mount Ashmore 1B site, and a study of fragments showed a large meteorite hit just before the Earth’s temperatures plunged.

“The identification of micro-structural and chemical features in drill fragments taken from the Mount Ashmore drill hole revealed evidence of a significant impact,” Glikson said, adding it was at least 50km wide and about 35mn years old.

A meteorite 100km wide hit Siberia at the same time, along with an 85km one in Chesapeake Bay, off the US coast of Virginia, followed by a large field of molten rock fragments over northeast America, he said.

“This defined a major impact cluster across the planet,” said Glikson.

He said the findings, published in the latest issue of the Australian Journal of Earth Sciences, could suggest a link between the impacts and a sharp fall in global temperatures which preceded the formation of the Antarctic ice sheet.

“This impact cluster hit Earth about 1mn years before the Drake Passage, the ocean gap between Antarctica and South America, opened up ... (which) allowed continuous circulation of the circum-Antarctic ocean current, isolating the Antarctic continent and allowing the onset of its large ice sheet, which acts as a thermostat’ for the Earth’s climate,” he added.

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Something hit Jupiter ... again!

Just as astronomers were telling the world that they figured out what gave Jupiter a black eye last July, yet another cosmic impact left a mark on the giant planet today. And this time, it was caught on video.

Actually, two of the world's best-known amateur observers of Jupiter both saw the flash of impact at 20:31 GMT today (4:31 p.m. ET). In Australia, Anthony Wesley captured a picture of the hit just before sunrise Friday (Down Under time). And in the Philippines, Christopher Go turned his pictures into a short video that was posted on SpaceWeather.com.

"I still can't believe that I caught a live impact on Jupiter," SpaceWeather quoted Go as saying.

It's not known exactly what caused the impact, but whether it was an asteroid or a comet, it's likely to have left a mark on Jupiter's cloud tops. So the call has gone out for all astronomers, professional and amateur, to monitor Jupiter in the hours ahead.

Great Black Spot analyzed
It was Wesley who first noticed the earlier hit on Jupiter, occurring on July 19, 2009. Actually, last year's impact occurred while the planet was turned away from Earth, so at the time, no one really knew what caused the "Great Black Spot" that persisted for months. But in the June 1 issue of The Astrophysical Journal Letters, astronomers say the culprit was likely an asteroid rather than a comet. That would make last year's impact the first time before-and-after pictures have been taken of an asteroid smashing into a planet.

To reach their conclusion, astronomers compared months' worth of Black Spot snapshots from the Hubble Space Telescope with images captured 15 years earlier, when broken-up pieces of Comet Shoemaker-Levy 9 plunged into Jupiter's atmosphere.

One team of astronomers, led by Heidi Hammel of the Colorado-based Space Science Institute, found key differences between the 1994 and the 2009 impacts. Ultraviolet imagery from 1994 revealed distinct halos around the impact sites, indicating that fine dust persisted after the impacts. The UV images also showed a strong, lingering contrast between the impact sites and the surrounding cloud cover. The astronomers took that as a sign that material from Shoemaker-Levy 9's cometary coma was hanging around in the upper cloud layers.

The aftermath of the 2009 impact, which hit with the force of thousands of nuclear bombs, was different. The UV images showed no halos, and the UV contrast quickly faded. The astronomers said the fast fade suggested that the particles left behind by last year's blast precipitated out of the clouds more rapidly. That would be "consistent with material that is more asteroidal than cometary in origin," they wrote.

The elongated shape of last year's "Black Spot" suggested that the asteroid came in at a shallower angle than the comet did. In a separate research paper, also appearing in The Astrophysical Journal Letters, astronomers analyze traces left behind in the Black Spot to figure out the path that the asteroid might have taken to collide with Jupiter. They conclude that the object could have come from the Hilda family of small bodies, a secondary asteroid belt consisting of more than 1,100 objects orbiting near Jupiter.

Anthony Wesley, the amateur astronomer who started it all, is listed as one of the authors of that paper.

In a NASA news release, Hammel said last July's impact was a testament to the contributions made by amateur astronomers. "This event beautifully illustrates how amateur and professional astronomers can work together," she said.

Now it's time for them to work together again, in the wake of today's smashing flash.

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Astronomers Perplexed by Jupiter Collisions

The huge, burning object that slammed into Jupiter last week still remains a mystery to scientists who are currently examining this latest impact on the gas giant.

The newest Jupiter collision was spotted Friday by amateur astronomers Anthony Wesley in Australia and Christopher Go in the Philippines. It occurred less than a year after another object whacked Jupiter last summer.

Wesley posted photos of the blazing fireball that signaled the collision to his website. They were taken from Broken Hill, Australia.

Scientists are now analyzing the impact, in hopes of being able to identify the cosmic object that crashed into the largest planet in our solar system.

For the time being, however, there is no consensus on what it was, said Heidi Hammel of the Space Science Institute in Boulder, Colo.

Hammel was the lead researcher of a study that was recently published in The Astrophysical Journal Letters, which determined that a rogue asteroid about 1,600 feet (500 meters) was the culprit in another spectacular crash on Jupiter that occurred on July 19, 2009.

It was Wesley, too, who first spotted the July 2009 Jupiter crash. His observations kicked off an international observation campaign to study the impact site.

Studies about Jupiter's latest impact are already underway, though no results have been released so far.

"We are working on the data analysis and I cannot say news on this," Agustin Sanchez-Lavega of the University of the Basque Country in Bilbao, Spain, told SPACE.com in an e-mail.

With this new collision coming less than a year after the July 2009 incident, researchers are rethinking current estimates of the frequency of such planetary impacts on Jupiter.

"Certainly the impact probability statistics seem to need revision, based on these two events within the past 11 months," Hammel told SPACE.com.

Jupiter is certainly no stranger to violent impacts. In 1994, the comet Shoemaker-Levy 9 broke into more than 20 pieces and pelted the gas giant repeatedly. At the time, astronomers estimated such impacts could occur on Jupiter every 50 to 250 years.

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