This week I’m concentrating on the Aristarchus region. Aristarchus crater was named after the Greek astronomer Aristarchus of Samos by an Italian mapmaker called Giovanni Riccioli.
The crater is relatively young, being formed approximately 450 million years ago and is one of the brightest craters on the nearside with an albedo almost double that of other similar features. It has a diameter of between 40 and 45km and a depth of 3.7km.
The following image of the Moon was taken by Jules and shows Aristarchus as the bright spot in the top left quadrant. It can be seen by the naked eye.
The Aristarchus area of the Moon is one of the most interesting and diverse regions on the nearside. It consists of a rectangular shaped plateau about 200km across which is located in the middle of the vast Oceanus Procellarum mare. This plateau was probably uplifted and tilted when the Imbrium basin was formed and has experienced much volcanic activity. The largest sinuous rille known, Vallis Schroteri, is found here and is about 160km long and up to 11km wide. The second article at the end of this post has a very interesting description of the head of the Vallis Schroteri rille and some great images.
The Aristarchus region has had many transient lunar phenomena (TLP) reported. When the Apollo 15 lander passed over this region in 1971 it recorded a significant rise in alpha particles which was believed to be caused by the decay of Radon-222. This radioactive gas has a half-life of only 3.8 days and is thought to be released through tidal stresses.
The following image shows the Aristarchus region. Aristarchus crater is on the left with Herodotus crater on the right and the Vallis Schroteri rille starting below it.
Nasa image from the Apollo 15 Mapping Camera
Some images of the Aristarchus area posted by users of the Moon Zoo forum:
Part of the collapsed walls of Aristarchus. Geoff
Latitude: 24.199° / Longitude: 312.434°
Impact melt in Aristarchus crater. Tom128
# ID: AMZ10036sv
# Latitude: 24.3744° / # Longitude: 312.405°
Interesting terrain in Aristarchus area. DJ_59
Latitude: 23.9853° / Longitude: 312.908°
More interesting terrain. Thornius
# ID: AMZ2000985
# Latitude: 23.5672° / # Longitude: 312.451°
An article from LROC about the geology of the central peak of Aristarchus crater and how the different rock types exposed by the impact help geologists to see what the interior of the Moon is made from.
An article from the Space Fellowship site discussing the Cobra Head feature which is thought to be the source vent of a tremendous outflowing of lava that formed the Vallis Schroteri rille.