August 23, 2007

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Striking Slips

image from SMART-1 ESA webpage. The caption is: “This is a SMART-1 AMIE image of a part of the Humorum basin showing strike slip faults (indicated in the right panel) and tectonic wrinkles due to crust deformation around a basin mascon (mass concentration or ‘local overweight’).”

The European Space Agency issued a press release yesterday reporting on a talk given by the SMART-1 team. They presented images of the Humorum Basin area and interpreted them in terms of the interplay of the basin and the later mare filling. Everything that was stated has been known for 20 to 30 years, with the exception of the reported discovery of strike slip faults. The caption seems to indicate that the green lines are strike slip faults and the purple are tectonic wrinkles. The purple feature appears to be a rille, not a wrinkle, and different segments of it are offset (where the green lines are drawn) as commonly occurs with rilles - see the Ariadaeus Rille for a large example. These offsets, called en echelon features, appear to be places where zones of weaknesses jump laterally, and there is no other evidence of faulting. Unfortunately, neither a location nor a scale is given for this image so it is difficult to locate it on other imagery to get complimentary views, and to see if the rille is previously shown. Discovery of strike slip faulting on the Moon would be important because it would require significant lateral movement of the crust, which has been proposed before but never convincingly documented. This new evidence, as presented in the press release, also fails to convince. Perhaps higher resolution imaging and digital topographic mapping from the upcoming Chinese, Japanese, Indian and American missions will be more revealing.

Chuck Wood

Yesterday's LPOD: Tiny Peaks

Tomorrow's LPOD: Halving the Depth


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