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Unexplained / Space exploration / Solar System / When Meteors Fell Like Rain / 


When Meteors Fell Like Rain

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About 500 million years ago, the sky rained meteorites after one of the largest collisions in the asteroid belt caused the breakup of a minor planet known as the "L chondrite parent body." At the time, earthly residents would have experienced a 100-fold increase in meteorite activity as compared to today. Even now, about 20 percent of meteorites that reach Earth are remnants of this great event.

As reported in the May 9 issue of Science magazine, this meteorite bombardment was recently confirmed through geologic discoveries on Earth. A team, led by Birger Schmitz while he was the Wiess Visiting Professor of Earth Science at Rice University, investigated five quarries over a 250,000-square-kilometer area in southern Sweden. The team found unique extraterrestrial forms of the mineral chromite at all five quarries. These chromite grains are only found in meteorites from the L chondrite breakup.

During the meteoritic rain Schmitz says "there would have been hundred times more fireballs in the skies than today." The meteorites that made it to the ground intact and the trace minerals from disintegrated meteorites were preserved within a layer of limestone deposited 480 million years ago.

Only 55 fossil meteorites embedded in stratified rock have ever been recovered, and Schmitz's group is credited with 50 of those. Schmitz says his team was "lucky to be looking in just the right place - a layer of lithified sediments that was forming on the sea floor immediately after this massive collision."

The group got a tip from quarry workers in Kinnekulle, Sweden, who were finding the meteorites on a regular basis. However, until Schmitz's team began investigating the site, the quarry workers simply discarded fossilized meteorites that were considered blemishes on their finished limestone.

Schmitz hopes to search additional sites in China and South America for fossilized meteorites and extraterrestrial chromite grains locked in limestone around the same time. "What we are doing is astronomy," he says, "but instead of looking up at the stars we are looking down into the Earth."



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