Latest revision as of 00:05, 25 July 2015

An Excess of Craters

Originally published July 24, 2004

Image Credit: Apollo 16 Metric Frame AS16-M0728

An Excess of Craters

I worked my way through college by measuring lunar craters for the System of Lunar Craters catalog published by the Lunar & Planetary Lab in the early 1960s. I am glad that this image of the middle of the lunar farside was not available then - it is a crater counter's nightmare! The dark-floored crater - one of the rare example of low albedo maria material far from the Big Backside Basin - is 53 km wide Kohlschutter (14N, 154E) and the entire area is pockmarked with smaller craters. Perhaps this is simply an ancient surface, as suggested by its many craters, but I wonder if the fact that they are mostly 15-30 km wide and appear similar in age means they are basin secondary craters? This area is surrounded by large impact basins - Freundlich-Sharonov to the E, Keeler-Heaviside to the S, Mendeleev to the W and, just visible as a limb flattening, Moscoviense to the N. The problem is all of these basin appear to be older than their putative secondaries! But Wilhelms, in his Geologic History of the Moon (p 85), also interprets this multitude of craters as secondaries and proposes Mendeleev as the source. So, if I'm wrong, I am in great company!