January 11, 2007

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Which Came First?

image by K.C. Pau, Hong Kong

Have you heard of Daniell? As a target for lunar imagers it has been pretty far down the list of must dos (at least until images because their lighting is too high. Most of these rilles are narrow, flat-bottomed ones that are roughly oncentric to the Serenitatis basin, and are thus similar to the Littrow and Chacornac rilles, east of the basin. It is interesting to try to figure out which came first, the Daniell Rilles that cut the Imbrium ejecta on the left side of the image, or the ejecta. The answer should be the ejecta was first, because the mare material of Somniorum and almost all other places is younger than the Imbrium impact. But it does look like the rilles may have been pre-existing and peppered by the ejecta. These lavas are brighter and more heavily cratered than the Serenitatis lavas so could concieveably be older than Imbrium’s 3.85 to 3.91 b.y. age. But it also doesn’t look like the ejecta feathers out onto the Somniorum lavas, but that the lavas embay the ejecta. This would mean the lavas are younger, but they are not as clearly defined in the rubbly ejecta as in the mare. And if the rilles are concentric to Serenitatis they would have formed as or after Serenitatis was filled with lava because it is the weight of mare material that causes a basin to subside and form circumferential rilles. So what do you think came first?

Chuck Wood

Technical Details:
10″ f/6 Newtonian + 5X barlow + Philips Toucam Pro.

Related Links:
Rükl Plate 14

Yesterday's LPOD: A Lovely Anachronism

Tomorrow's LPOD: Danny's Globe


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