March 29, 2014

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A Pre-Mare Moon

drawing by Don Davis

The Moon we see today is a consequence of millions of events that happened in the last four plus billion years. In 1970 artist Don Davis stripped off the maria and Copernican age craters to suggest how an earlier Moon looked, say about 3.8 b.y. ago, just after the Imbrium and Orientale basins formed. Very little mare had erupted by this time, with dark patches occurring only in the central, presumably deepest parts of the basins, and along the major basin rim fractures in Imbrium (similar to today's Veris and Autumni slivery lakes in Orientale). You can see the Iridum crater, whose southern rim was later submerged by Imbrium lavas. I am surprised to see the Serenitatis Basin superposed on the outer Imbrium basin ring (although some Imbrium ejecta seems to stripe it) for I always considered Serenitatis to be older than Imbrium. The one part of the Moon that looks relatively unchanged compared to present views is the southeastern highlands which is distant from most basins.

Chuck Wood
PS: Tonight was the first clear night since I received a new telescope mount, the iOptron ZEQ25. So I spent a pleasant, and relatively warm evening under the stars (and sometimes with my head in the instruction manual) rather than generating a new LPOD. But luckily here is a rebroadcast of an excellent one from Sept 17, 2008 that is still thought provoking. Enjoy.

Technical Details
I thank Don for making his drawings of the Moon's history publicly available!

Related Links
Don's web presence

Yesterday's LPOD: Out On a Limb

Tomorrow's LPOD: Over the Rainbow


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