02 February 2010


Who knew the solar system had a traffic problem?

In January, a sky survey of near-Earth asteroids found something so unusual that astronomers quickly used the Hubble Space Telescope to inspect it more closely.  What at first looked like a comet turned out to be the remnant of a spectacular cosmic collision: two asteroids recently smashing into one another.  It's estimated the space rocks had been hurtling toward one another at around 3 miles per second (five times faster than a speeding bullet). 

The result, seen in the Hubble photo above, is an unusual X-pattern near the nucleus of the object, with cometlike filaments of dust and gravel streaming back, due to radiation pressure from sunlight.  At the time this picture was taken, this asteroid/comet was some 90 million miles from Earth.  The nucleus that remains (the white dot at the left in the inset) is about 460 feet in diameter, longer than a football field. 

P/2010 A2 (its official name) belongs to a sort of asteroid aristocracy. It orbits among a family of asteroids that originated from a collisional shattering more than 100 million years ago. One fragment of that ancient smashup may have struck Earth 65 million years ago, triggering a mass extinction that wiped out the dinosaurs.

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