There was a full moon last night and while watching it I realized that I didn't know what else I was seeing. What causes it?
-
At Full Moon the differences in brightness are generally caused by ancient lava flows which the early astronomers mislabelled as "seas" or "maria" in Latin. These are greyer than the older mountainous areas of the Moon's surface. There are also a number of small bright spots where relatively recent asteroids have struck, often accompanied by systems of bright rays where material has been ejected from the impact. At Full Moon you have flat lighting, so you can't see craters and mountains, which are only visible with oblique lighting closer to the quarter Moons.
-
The dark areas are called Mare (sea in Latin). They generally are a rock called basalt, which is a form of solidified lava. The light regions are a rock called anorthosite, and are much older lunar crust than the Mare, which were caused by large impacts breaking through the crust to bring the molten material to the surface, roughly 3.5 to 3.9 billion years ago during a period called the Late Heavy Bombardment.
-
Impact Craters.
-
Craters & valleys : )