October 22, 2011
This is a detail from LROC image M104469044RC, showing an area in western Mare Serenitatis, west of Aratus D and north of Sulpicius Gallus at 8.02 East, 24.76 North. The image is only a few hundred meters across. The interesting features are the irregular pits at lower right, lower left and upper left, like very small versions of the more famous Ina, or D-Caldera. Features like this are turning up in several locations on the Moon. Ina was first noted by Ewen Whitaker in Apollo images, but others including good examples at Hyginus and in Mare Tranquillitatis were seen in Lunar Orbiter images and described by Pete Schultz in his massive Moon Morphology book. Now a concerted effort to find more has turned up 16 examples, single or in clusters, in several areas of the Moon, especially Mare Tranquillitatis (this image counts as just one cluster). Features very much like this were recently reported on Mercury, where a possible similarity to sublimation pits in Martian polar areas was noted. Since the features are now seen to be rather common on the Moon (but less so than on Mercury), it would seem likely that a lunar analog is better than a Martian one.
Philip J Stooke
Rükl plate 23
Yesterday's LPOD: Unsubtle Hues
Tomorrow's LPOD: Relictland