February 1, 2014

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image by Julio César Monje Bravo, Madrid, Spain

The Altai Scarp is one of the most dramatic basin rings on the Moon, casting long shadows in the lunar afternoon. But as Julio's image shows, the scarp is not continuous, taking an abrupt dip along its southwest edge. Two long shadows bracket a place where the scarp basically disappears. The broad flat plain to the left of the gap is the floor of an old battered crater, Rothman G. Did G form before or after the scarp? If afterward, that could account for the lowering of the scarp wall - the expanding shockwave from the crater-forming impact destroyed the basin rim. But the debris of the collapsed scarp isn't visible to the right. This area is covered by lava flows that perhaps covered the debris. If the crater formed first, the subsequent formation of the scarp would have cut right through a low spot - the crater rim and floor, so that the scarp would be lower than expected. This seems like a more reasonable explanation, but it is really arm-waving. That is what it is called when interpretation gets ahead of facts.

Chuck Wood
P.S.This is a replay of the Oct 30, 2010 LPOD - there were no comments then, are there some interpretations now?
P.P.S. - Today, Friday, was my last day of work at my day job. Now I work on Cassini, and will write more: an update of the Modern Moon, and a murder mystery set 165 years ago in the town I live in.

Technical Details
31 July 2010, 02:18 GMT (04:18 Local Time) from El Tiemblo, Avila, Spain. Guan-Sheng GS600 Newtonian 200mm f/4 telescope + Siebert Optics 3,5X telecentric lens (effective focal lens approx. 2.800mm.) + Imaging Source DMK31AU03.AS camera with Astronomik Planet IR Pro 742 filter. Processing: stacked image with AviStack2, post-processed with AviStack2 wavelets and unsharp mask of Photoshop CS4.

Related Links
21st Century Atlas chart 6.
Julio's website

Yesterday's LPOD: Ships Passing in the Daytime

Tomorrow's LPOD: Highland Rille


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