March 25, 2009

Scientists watch asteroid hit atmosphere

U.S. scientists say for the first time they have tracked an asteroid as it burst through the Earth's atmosphere from space and then found the pieces.

The historic episode occurred last year with the research team finding pieces of the asteroid in a Sudanese desert less than a day after it was seen burning through the sky, The New York Times reported Wednesday.

For the first time, we can dot the line between the meteorite in our hands and the asteroid astronomers saw in space, said Dr. Petrus M. Jenniskens, a scientist at the SETI Institute in Mountain View, Calif., who organized the search team and was the lead author of the article carried in the journal Nature.

Many pieces of asteroids have been found in the past. But before this discovery, scientists didn't know where any of the remnants had come from, said Michael E. Zolensky, a cosmic mineralogist at the Johnson Space Center in Houston.

Now scientists have 280 pieces, weighing a total of about 10 pounds -- all that remained of a car-sized rock that weighed an estimated 80 tons before it hit the atmosphere -- of a rare type of meteorite known as ureilites. Because the pieces show signs of being heated but not completely melted, scientists think they were once part of a much larger asteroid.

Scientists hope they can now determine the history of asteroids, the Times said.

It's like the first step toward a Rosetta stone of understanding asteroids, Zolensky said.