Lunar Day Twenty-Five

Abstract

We begin our studies tonight with another Moon walk around landmark crater Grimaldi (Figs. 26.1 and 26.2). Do you remember Sirasilis and its long rimae? Take a look now. Depending on how far the terminator has progressed at your time, you may get a wonderfully highlighted view of the longest rille on the lunar surface. Positioned between Grimaldi and the western bank of Oceanus Procellarum, you will find the ruins of crater Damoiseau. Formed in the Upper Imbrian period and spanning a modest 37 km in diameter, this smashed formation is also better viewed during the waning phase when the lighting is far less blinding. It shares part of its structure with Rimae Grimaldi, and you will notice a few areas where Damoiseau’s satellite craters have damaged the primary structure’s walls. This lighting condition also allows us to see the 150 km walled plain of Riccioli differently, too. Much like Grimaldi, it is a vast, empty expanse filled with lava flow.