Many round craters are visible on this image as are three mountain ranges that seem to form partial arcs of different circles. The arrows point in the directions of these ranges, but why are they circular in form? It turns out that they are actually the outer rims of gigantic craters known as impact basins. The two upper basins, Mare Imbrium (left) and Mare Serenitatis (right) are mostly filled with lava and have smooth interiors. Imbrium is over 700 miles in diameter and Serenitatis over 400 miles in diameter.
On the right side of the photo, the arrow appears to be pointing to two large craters, but look farther left and the battered arc of the Altai Scarp can be seen curving around their western margins. These mountains bound the western part of the Mare Nectaris impact basin which is over 500 miles in diameter, but has much less lava fill than the others. The Nectaris basin is very battered because it is the oldest of the three basins.
I was quite delighted to see parts of all three of these basins on the same field of view of the telescope. They remind me of rings of a circus, each with a different show to behold.
#marenectaris #mareserenitatis #mareimbrium #impactbasin
Eskildoodle Photos and Feelings 