02 April 2009

Scientists Track Down Fallen Star Treasure

From: http://www.technewsworld.com/story/66630.html
By Seth BorensteinAP 03/26/09 9:07 AM PT
Scientists eager to study an asteroid before its disintegration in Earth's atmosphere got their wish upon a star, so to speak. Through painstaking tracking and a desert search, they were able to recover fragments of a meteorite shot through with nanodiamonds. The discovery sheds light on the formation of planets and may help refine plans for avoiding a catastrophic asteroid strike.
For the first time, scientists matched a meteorite found on Earth with a specific asteroid that became a fireball plunging through the sky. It gives them a glimpse into the past when planets formed and an idea how to avoid a future asteroid Armageddon.
Last October, astronomers tracked a small nonthreatening asteroid heading toward Earth before it became a "shooting star," something they had not done before. It blew up in the sky, and scientists thought there would be no space rocks left to examine.
However, a painstaking search by dozens of students through the remote Sudan desert came up with 8.7 pounds of black jagged rocks, leftovers from the asteroid 2008 TC3. Those dark rocks were full of surprises and minuscule diamonds, according to a study published Thursday in the journal Nature...The asteroid, which mostly burned in the atmosphere 23 miles above the ground, is likely a leftover from chunks of rock that tried and failed to become a planet about 4.5 billion years ago, scientists said...Blowing it up -- as in the Bruce Willis movie "Armageddon" -- wouldn't be smart, because this type of asteroid turns out to be very much like a "traveling sandpile," Zolensky said. [See http://www.newscientist.com/article/mg20127015.600-how-to-save-the-world-from-an-asteroid-impact.html?DCMP=OTC-rss&nsref=online-news for a difference in opinion] "If you blow it up, all the pieces are heading toward Earth."
Instead, a spaceship-aided nudge would be more effective, said NASA Ames Research Center director Simon "Pete" Worden, another study coauthor. He is a longtime advocate of a worldwide program to plan for the threat of asteroids and comets hitting Earth.
"The real important issue is to understand the physics of these objects," Worden said.
There are many different types of asteroids, all classified from afar based on color and light wavelengths. This type is called "class F," and it turns out to be mostly porous and fragile. University of Maryland's McFadden said it's unlikely that a class F asteroid could be any danger to Earth -- even if it were bigger -- because of its porous makeup, which would cause it to break up before hitting.
The fragments of asteroid 2008 TC3 are full of metals, such as iron and nickel, and organics such as graphites, Zolensky said. Most interesting is that it has "nanodiamonds." These diamonds are formed by collisions in space and high pressure, and they are all over the rocks, making them glitter like geodes, he said -- but they aren't big.

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