LPOD Feb 16, 2008

A SIMPLE SCENE

image by Ladanyi Tamas, Veszprem, Hungary (south up)

When I used to study volcanoes a colleague who worked at the Hawaii Volcano Observatory said that a recent series of an eruptions produced such a complex landform that it could never be understood if it hadn't been witnessed. Sometimes I feel that way when looking at the Moon, except I wasn't there to witness any of it. Ladanyi's image of the Apollo 11 region in southwestern Mare Tranquillitatis doesn't look very complex, but I can't figure it all out. The mare is younger than the highlands to the south (at top), and the rilles and impact craters came later. In fact, the ejecta from Sabine covers part of the Hypatia Rilles so that crater must be younger than the rilles. The Arago Beta dome has always been something of a mystery - why is it so much steeper and rougher surfaced than most domes? And is Lamont really a buried two-ring impact basin? If so, why does it have massive mare ridges radiating away? With this lighting the unnamed ridge extending from Lamont towards Sabine is seen to cut off the outer ring of Lamont, implying that the ridge is more recent. Hmm. There is also a speculative suggestion from the arc of the ridge that it is the ghost rim of a large crater or small basin that extended all the way to the western shore where topography is on the terminator. In fact, a parallel curved ridge passing near the small crater Arago B could be an inner ring for the putative basin. Notice also that the mare surface inside this arc-bounded area is smoother and less ridged than any comparable area of Tranquillitatis. I wish I had seen this form, because its probably impossible to figure it all out, looking 3.6 billion years after the fact.

Chuck Wood

Technical Details
12.02.2008, 17:39 UT. 25cm Cassegrain reflector at f/14,2, ATK 1 HS CCD camera, stacked 28 frames from 1900, at average seeing

Related Links
Rükl plate 35
Ladanyi's webpage

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