Aorounga Impact Crater, Chad
Photo ID: P-46712
March 20, 1996
The impact of an asteroid or comet several hundred million years
ago left scars in the landscape that are still visible in this
spaceborne radar image of an area in the Sahara Desert of
northern Chad. The concentric ring structure is the Aorounga
impact crater, with a diameter of about 17 kilometers (10.5
miles). The original crater was buried by sediments, which were
then partially eroded to reveal the current ring-like appearance.
The dark streaks are deposits of windblown sand that migrate
along valleys cut by thousands of years of wind erosion. The dark
band in the upper right of the image is a portion of a proposed
second crater. Scientists are using radar images to investigate
the possibility that Aorounga is one of a string of impact
craters formed by multiple impacts. Radar imaging is a valuable
tool for the study of desert regions because the radar waves can
penetrate thin layers of dry sand to reveal details of geologic
structure that are invisible to other sensors. The image was
acquired by the Spaceborne Imaging Radar-C/X-band Synthetic
Aperture Radar (SIR-C/X-SAR) on April 18 and 19, 1994, onboard
the space shuttle Endeavour. The area shown is 22 kilometers by
28 kilometers (14 miles by 17 miles) and is centered at 19.1
degrees north latitude, 19.3 degrees east longitude. North is
toward the upper right. The colors are assigned to different
radar frequencies and polarizations as follows: red is L-band,
horizontally transmitted and received; green is C-band,
horizontally transmitted and received; and blue is C-band,
horizontally transmitted, vertically received. SIR-C/X-SAR, a
joint mission of the German, Italian and United States space
agencies, is part of NASA's Mission to Planet Earth program.
![[Aorounga Impact Crater]](CHAD.GIF)