November 3, 2011
image by Jocelyn Sérot, France
No, there wasn't a pyramid between Jocelyn and the Moon. His efforts to capture the well-librated limb included taking a series of limb-centered images - the pyramid is simply an area not on the limb. This view looks halfway across one of the Moon's oddest maria and impact basins. Mare Australe is an 880 km wide collection of mare-filled craters and low spots. This is a basin with no circular mountain rings to define it, and yet it was recognized 40 years ago as soon as spacecraft images covered this region right on the southeast limb. Early altimetry measurements suggested that Australe was a depression, as much as 2 km lower in the center than around the edges. There is also a mascon, an excess mass concentration, that is modelled as being due to a uprise of material from the mantle, as well as from the lava on the surface. The interpretation is that the Australe Basin is very ancient, having formed when the crust of the Moon was so warm that the mountain rims could not be supported, so they subsided. In this respect, Australe is similar to the South Pole-Aitken Basin, which retains some of its rim, but overall is much subdued. A final comment - the mare lava patches on the floor of Humboldt probably are tied to the proximity to deep crustal fractures associated with the Australe Basin.
Oct 5, 2011, 19h45 UT. T200 Newton, Barlow 2x, R filter, DMK 31. Registax 6 processing.
Rükl plate 76
Yesterday's LPOD: Mooned River
Tomorrow's LPOD: Way Around the Limb