Swift and Hubble probe an asteroid crash (w/ video)

Apr 28, 2011
Faint dust plumes bookend asteroid (596) Scheila, which is overexposed in this composite. Visible and ultraviolet images from Swift's UVOT (circled) are merged with a Digital Sky Survey image of the same region. The UVOT images were acquired on Dec. 15, 2010, when the asteroid was about 232 million miles from Earth. Labeled. Credit: NASA/Swift/DSS/D. Bodewits (UMD)

(PhysOrg.com) -- Late last year, astronomers noticed an asteroid named Scheila had unexpectedly brightened, and it was sporting short-lived plumes. Data from NASA's Swift satellite and Hubble Space Telescope showed these changes likely occurred after Scheila was struck by a much smaller asteroid.

"Collisions between asteroids create rock fragments, from fine dust to huge boulders, that impact planets and their moons," said Dennis Bodewits, an astronomer at the University of Maryland in College Park and lead author of the Swift study. "Yet this is the first time we've been able to catch one just weeks after the smash-up, long before the evidence fades away."

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Short narrated video about the asteroid collision.

Asteroids are rocky fragments thought to be debris from the formation and evolution of the solar system approximately 4.6 billion years ago. Millions of them orbit the sun between Mars and Jupiter in the main belt. Scheila is approximately 70 miles across and orbits the sun every five years.

"The Hubble data are most simply explained by the impact, at 11,000 mph, of a previously unknown asteroid about 100 feet in diameter," said Hubble team leader David Jewitt at the University of California in Los Angeles. Hubble did not see any discrete collision fragments, unlike its 2009 observations of P/2010 A2, the first identified .

The studies will appear in the May 20 edition of The and are available online.

Astronomers have known for decades that comets contain icy material that erupts when warmed by the sun. They regarded asteroids as inactive rocks whose destinies, surfaces, shapes and sizes were determined by mutual impacts. However, this simple picture has grown more complex over the past few years.

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Animation of (596) Scheila collision and dust plumes. Includes some sound effects.

During certain parts of their orbits, some objects, once categorized as asteroids, clearly develop comet-like features that can last for many months. Others display much shorter outbursts. Icy materials may be occasionally exposed, either by internal geological processes or by an external one, such as an impact.

On Dec. 11, 2010, images from the University of Arizona's Catalina Sky Survey, a project of NASA's Near Earth Object Observations Program, revealed Scheila to be twice as bright as expected and immersed in a faint comet-like glow. Looking through the survey's archived images, astronomers inferred the outburst began between Nov. 11 and Dec. 3.

Three days after the outburst was announced, Swift's Ultraviolet/Optical Telescope (UVOT) captured multiple images and a spectrum of the asteroid. Ultraviolet sunlight breaks up the gas molecules surrounding comets; water, for example, is transformed into hydroxyl and hydrogen. But none of the emissions most commonly identified in comets, such as hydroxyl or cyanogen, show up in the UVOT spectrum. The absence of gas around Scheila led the Swift team to reject scenarios where exposed ice accounted for the activity.

The Hubble Space Telescope imaged (596) Scheila on Dec. 27, 2010, when the asteroid was about 218 million miles away. Scheila is overexposed in this image to reveal the faint dust features. The asteroid is surrounded by a C-shaped cloud of particles and displays a linear dust tail in this visible-light picture acquired by Hubble's Wide Field Camera 3. Because Hubble tracked the asteroid during the exposure, star images are trailed. Labeled. Credit: NASA, ESA, and D. Jewitt (UCLA)

Images show the asteroid was flanked in the north by a bright dust plume and in the south by a fainter one. The dual plumes formed as small dust particles excavated by the impact were pushed away from the asteroid by sunlight. Hubble observed the asteroid's fading dust cloud on Dec. 27, 2010, and Jan. 4, 2011.

The two teams found the observations were best explained by a collision with a small impacting Scheila's surface at an angle of less than 30 degrees, leaving a crater 1,000 feet across. Laboratory experiments show a more direct strike probably wouldn't have produced two distinct dust plumes. The researchers estimated the crash ejected more than 660,000 tons of dust -- equivalent to nearly twice the mass of the Empire State Building.

"The dust cloud around Scheila could be 10,000 times as massive as the one ejected from comet 9P/Tempel 1 during NASA's UMD-led Deep Impact mission," said co-author Michael Kelley, also at the University of Maryland. "Collisions allow us to peek inside comets and asteroids. Ejecta kicked up by Deep Impact contained lots of ice, and the absence of ice in Scheila's interior shows that it's entirely unlike comets."

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User comments : 10

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plasticpower
not rated yet Apr 28, 2011
So if this impact is comparable to a small 100 kiloton nuke, I wonder what sort of damage a larger nuke would do. Like the "full" version of the Tsar Bomba (100 megatons). I think we have right now the capability to defend this planet from asteroids.
Megadeth312
5 / 5 (3) Apr 28, 2011
So if this impact is comparable to a small 100 kiloton nuke, I wonder what sort of damage a larger nuke would do. Like the "full" version of the Tsar Bomba (100 megatons). I think we have right now the capability to defend this planet from asteroids.


We could quite possibly destroy an impending asteroid, or (more likely) divert it enough to miss Earth, however we'd have to detect it first. There in lies most of the actual danger, it will be a while before we have eyes over 100% of the sky at all times.
eigenbasis
not rated yet Apr 28, 2011
I like that the collision video has the "Includes some sound effects." Because in space there isn't a medium for sound waves to propagate through!
Stavanger
not rated yet Apr 28, 2011
We could quite possibly destroy an impending asteroid, or (more likely) divert it enough to miss Earth, however we'd have to detect it first. There in lies most of the actual danger, it will be a while before we have eyes over 100% of the sky at all times.

And in a effectively way. there's also the fact that we can only see something in space if the sun is barbecuing it.
Party_Bus_Dc
not rated yet Apr 29, 2011
Here is a similar story

The strange metamorphosis astronomers observed in an asteroid late last year was likely caused by a collision with another space rock, according to two new studies.

In December 2010, astronomers noticed that an asteroid named (596) Scheila had brightened unexpectedly. Not only that, the space rock was sporting some new and short-lived dust plumes. These changes were probably brought on by a smashup with a smaller asteroid, according to the studies, which were based on observations made by NASA's Spitzer and Hubble space telescopes.
alanborky
1 / 5 (1) Apr 29, 2011
Supposedly critters like Scheila bumping into each other's how planets're formed.

You won't make any planets, going by these standards, but you will make plenty of dust - maybe the 'solar dust disk leads to planetary formation' model's back to front, on this evidence.
Skeptic_Heretic
5 / 5 (2) Apr 29, 2011
Supposedly critters like Scheila bumping into each other's how planets're formed.
No it isn't. Collisions are not accretion.
You won't make any planets, going by these standards, but you will make plenty of dust - maybe the 'solar dust disk leads to planetary formation' model's back to front, on this evidence.

Accretion is a resultant effect of electrostatic and gravitational attraction and cohesion, not high speed collision.
GSwift7
1 / 5 (1) Apr 29, 2011
Swift and Hubble probe an asteroid


I didn't not!!! I'm being framed.

But none of the emissions most commonly identified in comets, such as hydroxyl or cyanogen, show up in the UVOT spectrum


So, what did show up? I guess that'll be another paper.

I think we have right now the capability to defend this planet from asteroids


Only the ones with orbits that we can intercept. Even with a long time to prepare, there are orbits that we would have a very hard time intercepting. In order to make a nuke effective in space, the detonation would need to be very close to the surface of the rock and you would want the explosion on the side, not the front of the rock. That means you would not want to approach it head-on at 20,000kph. We would actually be very lucky if an asteroid happend to be headed towards us on a trajectory that allowed us to reach it in time. It takes months or years to slingshot around planets and such, even if everything is in the right place
GSwift7
1 / 5 (1) Apr 29, 2011
continued:

Almost all of the energy of a nuke is in the form of light. The shockwave you get here on Earth wouldn't happen in space. The effect of a nuke on an asteroid would be to vaporize a small part of the surface. It wouldn't be much really. Remember that it takes a transfer of momentum to change the path of an asteroid, not just energy, but also a component of mass. There's not really much mass in a nuke explosion. All the destructive force you get on Earth comes from the air pressure really. Scorching the side of the asteroid with intense light would have very little effect on its path. In order to change the path you need to blow a piece off or vaporize a large volume of material on one side. A nuke explosion is too brief to vaporize that much material, especially a very very very cold asteroid. Did you know that meteors are cold when they land? The outer surface ablates on entry, but the inside is so cold that it doesn't heat up even when the outside is vaporising.
GSwift7
1 / 5 (1) Apr 29, 2011
Also, you need to be very precise about how you apply whatever force you can generate on the asteroid. If you aren't carefull you could produce a change in both direction AND speed, which could combine/counteract to still produce a collision path. Or, if you hit it off-axis you might just make it spin rather than change its course much.

Conclusion:

We will not be able to say that we can properly defend the planet from asteroids within our lifetime, and possibly not in our grandchildren's lifetimes either.