Astronomers observe impact of asteroid in real time
www.chinaview.cn 2009-03-27 16:19:37   Print

    LONDON, March 26 (Xinhua) -- International astronomers observed for the first time from start to finish the impact of an asteroid, 2008 TC3, the March 26 issue of journal Nature reported.

    Asteroid 2008 TC3 moving toward Earth, disintegrated in the atmosphere last October, yielding crucial evidence for the study of asteroids and planets.

    It also gave astronomers a rare opportunity to connect a dot in the sky with rocks in their hands.

    "We have a lot of meteorites on the ground and a whole lot of asteroids up there, and forging a link is not easy," Don Yeomans, manager of NASA's Near-Earth Object Program Office, was quoted as saying by Nature.

    Around midnight on Oct. 6, 2008, an astronomer first spotted and reported the asteroid to the U.S. Minor Planet Center.

    Following calculations, it was found that the asteroid was unusually close to Earth.

    However, its brightness suggested it was only a few meters wide and, assuming it was a common rocky asteroid, would probably split into fragments soon after entering Earth's atmosphere.

    Astronomers of U.S. space agency NASA calculated the asteroid would hit Earth's atmosphere in less than 13 hours, and the impact site would be northern Sudan. NASA immediately circulated an electronic bulletin to a worldwide network of astronomers.

    Although several small asteroids such as 2008 TC3 hit the Earth each year, researchers had never spotted one before it struck.

    The unexpected discovery of 2008 TC3 provided a unique opportunity to study an asteroid and its demise in real time. About an hour before impact, astronomers from 26 observatories worldwide had already captured and submitted about 570 observations.

    Asteroid 2008 TC3 hit the top of the atmosphere at about 12,400meters per second. The impact of rock atoms with air molecules created a brilliant flash that lit up the desert below.

    Less than 20 seconds after its entry, the studies show pressure on the asteroid triggered a series of explosions that shattered it, leaving a trail of hot dust.

    In the months following the asteroid's breakup, international astronomers searched for its fragments in the desert area of Sudan. The most recent search, completed in March, brought the tally of fragments to about 280. This is the first time scientists had ever recovered fragments from an asteroid detected in space.

    Lab tests confirmed the samples were ureilites, a type of meteorite thought to originate from asteroids that have melted during their time in space. Only 0.5 percent of objects that hit Earth yield fragments in this category. But 2008 TC3's fragments were strange even for ureilites: they were riddled with an unusually large number of holes.

    The findings suggest 2008 TC3 broke from the surface of a larger asteroid.

    The astronomers said future studies of the chemistry of meteorites could help reveal the history of its parent asteroid. Moreover, the new finding might also eventually yield clues to how planets are formed.

    They said the asteroid belonged to a group called F-class asteroids. These asteroids reflect very little light, and scientists had been unsure what they were made of. Now, this new evidence "opens a huge window."

Editor: Fang
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