Evidence supports near-Earth asteroid theory

By Cara Miller

Arizona Daily Wildcat

With the help of telescopes and computer simulation, UA scientists may have discovered a second asteroid belt consisting of moon fragments.

After 12 years of studying near-Earth asteroids, (usually five- to fifty-meter asteroids), University of Arizona Spacewatch has identified five asteroids that have a circular orbit similar to the Earth's.

One of only three programs like it in the world, UA Spacewatch dedicates itself to locating near-Earth asteroids.

"We find a lot of asteroids, but maybe only one in 1,500 are near-Earth asteroids," said project participant Robert Jedicke.

"We haven't finished the research yet, but we do have some evidence that the belt exists," he said.

Planetary sciences graduate student William Bottke said the asteroids in the belt are unusual because most follow an elliptical path.

"Most asteroids we see out in space originated from the main asteroid belt between Mars and Jupiter," he said. "But because these don't follow an elliptical path we had to look elsewhere for the source of these asteroids."

He said the asteroid belt between Mars and Jupiter is unlikely to produce bodies with Earth-like orbits.

Subsequently Bottke devised a computer simulation to trace the evolution of asteroids.

He said the computer simulation suggests that a large asteroid colliding with the moon within the last 10 million to 20 mil

lion years might have ejected fragments from the moon's surface into space. Some fragments would have orbited the sun, forming the belt.

Bottke said soil samples from the Apollo mission to the moon support his claim because they are chemically identical to meteorites found on Earth.

Bottke said these findings are important because they might give some clues to the evolution of the solar system.

"Understanding what is happening on other planets is fundamental to understanding what's happening on ours," Bottke said.

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