December 27, 2013
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.
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.
21st Century Atlas chart 1.
Yesterday's LPOD: 33 And Counting
Tomorrow's LPOD: Looking Over the Shoulder of a Lunar Scientist