December 27, 2013

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Two Little Known Valleys

left image by George Tarsoudis, and right image from LRO QuickMap

In an excellent new mosaic of the area north of Mare Crisium, George noted a linear shadow striking towards the southeast from the southern edge of the complex crater Geminus. The much higher Sun LRO Quickmap reveals two linear features here; George's shadowed feature is the southern one. I had not noticed these before and down't know what tectonic forces caused their formation. The top one looks like a typical, but wide, flat-floored graben; it is about 60 km long and 7 km wide. The southern linear feature has more of a gentle vee-shaped floor and trends in a very slightly different direction than the northern valley. The northern valley is exactly radial to the central peaks of Geminus, suggesting that it could be a secondary crater chain or radial fracture associated with that crater. But Geminus is very fresh - notice its sharp rim crest - and these valleys are not. Nor are they radial to any nearby basin, and in fact, they cut at an oblique angle the Geminus - Berosus outer rim of the Crisium Basin. George's linear shadow does mark a little known pair of valleys, but their origin remain uncertain to me.
Chuck Wood

Technical Details
Dec 20, 2013. Telescope SkyWatcher 14 inch @f/4.5, camera QHY 5L-II, filter IR-pass, barlow 3X, mosaic 2 images. Condition with pure seeing, good transparency.

Related Links
21st Century Atlas chart 1.
George's website

Yesterday's LPOD: 33 And Counting

Tomorrow's LPOD: Looking Over the Shoulder of a Lunar Scientist


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