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Was Earth walloped
360 million years ago?Massive craters believed caused by comet
March 22, 1996
Web posted at: 8:35 a.m. ESTLOS ANGELES (CNN) -- Scientists presented evidence this week of a series of impact craters in the central African country of Chad. Chad is believed to be the site of a string of large craters that scientists theorize were formed when comet fragments slammed into Earth 360 million years ago. (391K QuickTime Movie)
The craters were first detected in radar images taken of the Earth from the space shuttle Endeavour, in April and October 1994. The pictures, taken with a radar called SIR-C/X-SAR (short for Spaceborne Imaging Radar C/X-band Synthetic Aperture Radar), show three circular marks, each about 10 miles in diameter. They are near a known impact crater in an area called Aorounga, in northern Chad.
NASA scientists believe they were created when an asteroid or comet broke apart, then hit the Earth's surface, much as the Shoemaker-Levy 9 comet broke into pieces and smashed into Jupiter's atmosphere in 1994. The existence of the crater dubbed Aorounga South, the largest of the three major craters in the group, had already been confirmed through ground studies. The other two, Aorounga North and Aorounga Central, must still be confirmed.
The craters in Aorounga are only the second chain of large craters known on Earth, according to geologists from NASA's Jet Propulsion Laboratory in Pasadena. Scientists have proposed further study to verify that the craters were created in an impact, but Michael Rampino, an Earth scientists at New York University, said it was "a good bet" that the features found in Chad were a new chain of impact craters.
The first known chain of impact craters is made up of eight crater-like geological structures stretching 435 miles, from southern Illinois to Kansas.
The Associated Press contributed to this report.
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