NASA's Mars Global Surveyor shows boulders in large ripples formed by an ancient catastrophic flood in Mars' Athabasca Vallis on Mars.

figure 1 for PIA06878
Figure 1

Researchers' goal in taking this image was to look for boulders in the large ripples formed by an ancient catastrophic flood in Mars' Athabasca Vallis. The Mars Orbiter Camera on NASA's Mars Global Surveyor spacecraft captured this image on Dec. 25, 2003, with use of an enhanced-resolution technique called compensated pitch and roll targeted observation.

The flood-deposited megaripples had been seen in earlier, lower-resolution images from the same camera. They are the only good examples known of ripples formed in a giant catastrophic flood anywhere on Mars. Their presence indicates that large amounts of water poured rapidly through this area, based on resemblance to similar megaripples in catastrophic flood sites on Earth. The ripples in Athabasca Vallis were buried for some period and later exhumed. Strange, round features on top of some of the ripples and the adjacent plains are products of erosion and removal of the overlying layer. Finding boulders in the ripples would help constrain estimates of the power of the floods. However, the image does not show boulders in the ripples, implying either that the rocks that make up these features are smaller than about 1 to 2 meters (3 to 7 feet) in diameter or that the ripple sediments have not been completely exhumed.

The image covers an area 3 kilometers (2 miles) wide, near 9.5 degrees north latitude and 203.7 degrees west longitude. Pixel size is about 1.5 meters (5 feet) by one-half meter (1.6 feet). North is up and sunlight illuminates the scene from the lower left.

Mars Global Surveyor is managed by NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, for the NASA Science Mission Directorate, Washington.

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