December 4, 2012
The Adams Family
Clementine image (left) from Map-A-Planet and LRO (right) from QuickMap
A strange one-sided ray on Howard Eskildsen's image of two days ago seemed worthy of further attention and it is. As pointed out in yesterday's LPOD the broad ray extends from the bright-rimmed, flat-floored crater just west of Adams. The crater is Adams B, which is unusual for its decidedly elliptical shape of 27 x 38 km; it is about 3 km deep. The ray is as wide as B's long axis and extends perpendicular from it for about 150 km and then thin strands continue that much further. I don't know of any other one-sided ray craters on the Moon. What immediately comes to mind is a very low angle oblique impact with butterfly wing rays 90° from its elongated axis. That could be the explanation except that there is no evidence for a ray to the south east. The closeup LRO image reveals a fresh crater - as its bright rim indicated even from Earth - with a flat plateau on the right side of its floor. Zooming in on this area on QuickMap shows the unit to be an coarse impact melt with large crenulations where it changes from smooth-surfaced to a more rugged texture. While in QuickMap look at the ray-covered area to the northeast of B. With the lower Sun of LRO the ray is not visible as an albedo feature but it corresponds to a topographically slightly muted surface, as if veneered by a greater depth of material than in normal rays. Adams B is definitely a feature to keep investigating. And while in the neighborhood note the faint rays around the central peak crater Palitzsch B at top-center of the Clementine image. It looks like it could be an oblique impacr crater but at a higher angle for the rays are quite visible on all sides except the southeast.
Rükl plate 76
21st Century Atlas charts 5, L3 & B3.
Yesterday's LPOD: Still On the Limb
Tomorrow's LPOD: No I Won't