discovery

New analysis makes it possible to 'know our enemy'
David Chandler, MIT News Office
August 13, 2008

For the last few years, astronomers have faced a puzzle: The vast majority of asteroids that come near the Earth are of a type that matches only a tiny fraction of the meteorites that most frequently hit our planet.

Since meteorites are mostly pieces of asteroids, this discrepancy was hard to explain, but a team from MIT and other institutions has now found what it believes is the answer to the puzzle. The smaller rocks that most often fall to Earth, it seems, come straight in from the main asteroid belt out between Mars and Jupiter, rather than from the near-Earth asteroid (NEA) population.

The puzzle gradually emerged from a long-term study of the properties of asteroids carried out by MIT professor of planetary science Richard Binzel and his students, along with postdoctoral researcher P. Vernazza, who is now with the European Space Agency, and A.T. Tokunaga, director of the NASA Infrared Telescope Facility.

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ScienceDaily (July 10, 2008) — When observing with the GEMINI telescopes, two astronomers from Brazil and the United States discovered for the first time asteroids that are similar to “ordinary chondrites”, the most common meteorites found on Earth. Until now, astronomers have failed to identify their asteroidal sources because of the various geologic processes that occur after the meteorites are ejected from their asteroidal parent body.

Astronomy & Astrophysics is publishing the first discovery by T. Mothé-Diniz (Brazil) and D. Nesvorný (USA) of asteroids with a spectrum similar to that of ordinary chondrites, the meteoritic material that most resembles the composition of our Sun. Most of the meteorites that we collect on Earth come from the main belt of asteroids located between Mars and Jupiter [1]. They were ejected from their asteroidal “parent body” after a collision, were injected into a new orbit, and they finally felt onto the Earth. Meteorites are a major tool for knowing the history of the solar system because their composition is a record of past geologic processes that occurred while they were still incorporated in the parent asteroid.

From UPI.COM

STOCKHOLM, Sweden, June 13 (UPI) -- A massive meteorite weighing a staggering 2,607 pounds has been found near the northern Swedish village of Kitkiojarvi, officials say.

Thomas Osterberg, one of the two people who found it, said it was the biggest meteorite ever found in Sweden, the Swedish news agency TT reported.

He said it was egg-shaped, about one meter high with a diameter of about 70 centimeters at its broadest.

The finders say they hope to sell the whopper to the Swedish Museum of Natural History.

"It must stay in Sweden," Osterberg said.

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