Lunar Craters Messier and Messier A
Taken by Howard Eskildsen on April 11, 2020 @
Ocala, Florida, USA
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Date Taken: 2020:04:20 14:35:34
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Details:
Messier Shadows
The telescopic image (figure 1), taken at low sun-angle, shows ear-like shadows extending east of Messier, which by coincidence are in the opposite direction of the downrange rays from the oblique impact. This implies that the crater rim is higher at mid crater, perpendicular to the path of the oblique impact. The Messier A shadow appears more typical without the “ears” shown by Messier. However, its rim has an uneven, wrinkled appearance at mid crater perpendicular to the impactor path of travel.
The LROC draw/search tool was used to generate elevation profiles. Figure 2 verifies that the uprange portion of Messier’s crater wall, as well as the downrange portion are much lower than the middle segments of crater wall. The uprange wall is slightly higher than the downrange wall. Figure 3 shows the uprange wall of Messier A to be similar in elevation than the middle wall segments, though it is slightly higher than its downrange wall. Also, the LROC image shows clumped wings of ejecta in the same area as the “wrinkles” seen on Messier A in Figure 1.
I wonder if the pattern of low rim elevation on the uprange and downrange portions compared to mid crater rim elevations is a general characteristic of an oblique crater, or if it is unique to this crater pair. I will be looking.
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