Recovered Pieces of Asteroid Hold Clues to Early History

By | March 26, 2009

Scientists who for the first time tracked an asteroid on a collision course with Earth, and watched as it exploded in the atmosphere, have now picked up some of the remnants on the ground.

The discovery and analysis of the meteorites, reported in Thursday’s issue of Nature, give scientists solid data on the composition of meteorites that originate from at least one type of asteroid, known as F-class.

Millions of asteroids, mostly small, whirl around the solar system, and over the years people have picked up tens of thousands of meteorites, the surviving rock fragments of asteroids that collide with Earth.

“But we don’t know where a single one of them comes from,” said Michael E. Zolensky, a cosmic mineralogist at the Johnson Space Center in Houston, during a NASA-sponsored news conference on Wednesday.

That changed when Petrus M. Jenniskens, a scientist at the SETI Institute in Mountain View, Calif., organized a search team to comb through a Sudan desert to look for pieces of an asteroid that had been spotted less than a day before it hit Earth last year.

“For the first time, we can dot the line between the meteorite in our hands and the asteroid astronomers saw in space,” said Dr. Jenniskens, the lead author of the Nature paper.

image: Electron microscope images of the meteorite showed an unusual hodge-podge structure indicative of a type known as ureilites. Unusual even for ureilites, the meteorite was highly porous with cavities as seen in image “C,” shown at bottom left. The meteorite even contained tiny diamond crystals.

The 280 pieces, about 10 pounds in total, are of a rare type of meteorite known as ureilites. The hodgepodge of minerals in ureilites indicates they were heated up but not fully melted, suggesting that they were once part of a much larger asteroid that possessed planetlike geological processes.

Because ureilites are now linked to F-class asteroids, also rare, the hope is that scientists can now determine the history of asteroids, which contain some of the most primitive materials left over from the early solar system.

“It’s like the first step towards a Rosetta stone of understanding asteroids,” Dr. Zolensky said.

via New York Times

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