365 Days of the Moon -- August 23, 2014
Posidonius, Le Monnier, Rima Chacornac, Rima Bond, and the Serpentine
I love floor-fractured craters! Although no two craters are alike, there is a certain monotony to terraced walls...central peak...repeat.
Floor-fractured craters are a nice diversion from that pattern. Here we see 58-mile wide Posidonius on the eastern edge of Mare
Serenitatis. Perhaps three billion years ago, lavas from the same magma chambers that flooded Mare Serenitatis welled up through fractures
in the floor of Posidonius and also flooded the crater to the point where even the central peak was covered. As the lava solidified into a
basalt field, volcanic uplift further pushed up the now solid floor of Posidonius and created the system of rilles, or cracks across the
crater floor. The result of this upward pressure created the classic "oatmeal cookie" appearance of the floor-fractured crater.
Below Posidonius is the half-moon bay of the crater Le Monnier. This was the landing site of the Russian Lunokhod 2 rover that traveled
nearly 30 miles on the Moon back in 1973.
The rille Rima Chacornac extends below Posidonius while Rima Bond meanders along the right of the image. At the left is the winding wrinkle
ridge popularly called the Serpentine Ridge.
Image taken through a Celestron 11 Edge HD, 2.5X Powermate, and a Skyris
Image copyright Robert Reeves 2014