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February 3, 2010

First Ever Interplanetary Collision Witnessed by Hubble

Between Mars and Jupiter is the asteroid belt, a large collection of small rocks left over from the formation of the solar system. The vast number of objects within the asteroid belt has led astronomers to predict that collisions between asteroids should be relatively common. For the first time, astronomers may have found one of these impacts.

At first glance, this debris tail looks similar to that of a comet. As they approach the sun, comets (which are mostly made of various ices) will give off splendid tails as the ices warm up and turn to gasses. However, the crucial difference is in the X-shaped pattern in the close up image. You see a clear difference from these images of a fragmenting comet (also imaged by Hubble). "This is quite different from the smooth dust envelopes of normal comets," says principal investigator David Jewitt of the University of California at Los Angeles. There are also other inconsistencies with the comet hypothesis. One such example is that the orbit of this object (creatively named P/2010 A2) is much closer to the sun than we would expect for a comet made up of ice.

So, if it's not a comet, that opens up the possibility of it being a high energy collision. Speeds in such a collision are estimated to be close to 11,000 miles per hour, five times faster than a rifle bullet! "If this interpretation is correct, two small and previously unknown asteroids recently collided, creating a shower of debris that is being swept back into a tail from the collision site by the pressure of sunlight," says Jewitt. So right now, the evidence is strong that we have fulfilled every little boys dream, watching rocks crash together at high speeds in space.

Source: HubbleSite
Collision Image Credit: NASA, ESA, and D. Jewitt (UCLA)
Fragmentation Image Credit:NASA, ESA, H. Weaver (APL/JHU), M. Mutchler and Z. Levay (STScI)