Scientists have completed their study of a meteorite that struck Southwest Wisconsin nearly three years ago. About eight pounds of fragments from what's called the 'Mifflin Meteorite' have been recovered. A UW-Madison lab is one of the agencies that has looked at some of the fragments, using sophisticated equipment like an electron microscope. UW Geology Professor John Valley says it's some very old rock — older than the Earth — called 'L5 chondrite.' "They're believed to have come from a a single asteroid that was destroyed, probably by collision with a second asteroid, 470 million years ago." Valley says the 'Mifflin Meteorite' matches up with very old L chondrite fragments found in quarries in China and Sweden. he says the Rock Elm crater near Menomonie was likely formed at the same time as those overseas sites, also pummeled by L chondrite debris. Valley says the meteor that exploded over Russia last week was much larger than the perhaps one-meter-in-diameter object that hit Wisconsin and nearby states in 2010.
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