Rima Hyginus is a linear rille which branches to the northwest and the east of Hyginus crater. The rock slide shown in the Featured Image is located on the northern wall of the eastern branch of Rima Hyginus at 7.393°N, 7.954°E. Bright boulder-rich material from the edge of the rille slid down the wall, possibly during a period of tectonic shaking due to a moonquake or forces associated with a nearby impact. A trio of large boulders also left trails as they tumbled down the rille's wall.
Rima Hyginus formed through faulting, and is actually a graben. A graben is a section of the crust that sunk as two parallel faults pulled apart. Remember, the term linear rille is just a fancy way of saying a graben. After the graben formed Rima Hyginus, the landscape changed again due to volcanic activity, specifically the collapse craters easily seen in the the WAC context image (below). The craters follow the slight curve of the rille, which indicates that they are not simply a chain of secondary craters that happened to land on top of the existing graben. These craters also do not have raised rims, and they probably formed when the volcanic structures underlying the graben collapsed.
Examine more of Rima Hyginus in the full LROC NAC!
You can read more about the Hyginus region in the Icarus paper, "An igneous origin for Rima Hyginus and Hyginus crater on the Moon."
Posted by Sarah Braden on June 13, 2012 09:00 UTC.