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Facing the Impact Hazard

Facing the Impact Hazard
Facing the Impact Hazard Might these faint circles be the scars of past blows to Earth's surface? The concentric ring structure left of center is the Aorounga impact crater in northern Chad. Scientists are using radar imagery to study the possibility that Aorounga is part of a "crater chain" formed several hundred million years ago by pieces of an asteroid or comet. A second crater appears to sit in the middle of this picture, and the dark, partially circular trough at right of center could be a third. The area shown is 45 by 40 kilometers (28 by 25 miles) in size. This image, captured in 1994 by the Spaceborne Imaging Radar-C/X Band Synthetic Aperture Radar onboard the space shuttle, penetrated the Sahara's sand to reveal these otherwise invisible geologic features. JPL/NASA