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MADISON - Researchers in the University of Wisconsin-Madison Department of Geoscience had the opportunity Friday morning to analyze a rock fragment they believe is from the meteor that blazed through the skies over parts of Wisconsin and Iowa Wednesday night.
The rock measures approximately 2 inches by 3/4 of an inch and weighs 7.5 grams. It contains gray, white, and reddish minerals and one side is covered by a thin "fusion crust" of darker material that forms when a meteor heats up as it passes through Earth's atmosphere. It was found around 8:30 a.m. Thursday by a farmer west of Madison. The fragment had hit the roof of his shed.
Though the rock was only at the university for a short time, UW-Madison meteorite experts Noriko Kita and Takayuki Ushikubo used a scanning electron microscope and X-ray spectrometer to begin to analyze the surface mineral composition of the rock. They identified the presence of magnesium, iron, and silica-containing compounds, including the common minerals olivine and pyroxene. They also found iron-nickel metal and iron sulfide, which are often seen in primitive meteorites.
The scientists hope to get the opportunity to conduct more detailed studies of fragments of the meteor. Such analyses may be able to tell them about the composition of the solar system and processes that shaped the early Earth. Anyone finding pieces of the meteorite are asked to bring them to the UW-Madison Geology Museum at 1215 W. Dayton St. in Madison.
"Until we look at more samples and are able to take some measurements, we won't know what kind of meteorite it is," says Kita, director of the department's Ion Microprobe Laboratory. UW-Madison has some of the world's most sensitive analytical equipment for studying such material.
Because the piece they studied only has fusion crust on one side, it is almost certain there are more pieces of the meteorite scattered across the landscape of southern Wisconsin, says UW-Madison geoscience professor John Valley. "If the meteorite had broken up high in the atmosphere it would have developed a fusion crust that completely covered the exterior. This doesn't have that, so it broke up low enough that I'd have to say more of it hit the ground," he says.
It is extremely unusual to identify pieces from known meteorite falls, says UW-Madison Geology Museum director Richard Slaughter. The museum has pieces of seven of the 12 previous known meteorite falls in Wisconsin, most of which are more than 50 years old.
More information about meteorites can be found on the museum's webpage at http://www.geology.wisc.edu/~museum/meteorite.html.