Wednesday, June 13, 2012

LROC: Rock silde in Rima Hyginus

A rock slide along a section of the northern wall of Rima Hyginus. LROC Narrow Angle Camera (NAC) observation M111545012R, LRO orbit 1572, October 30, 2009; angle of incidence 27.62° at a native resolution of 0.48 meters from 47.28 kilometers. See the 576 meter-wide field of view of the area in the LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Sarah Braden
LROC News System

Rima Hyginus is a linear rille which branches to the northwest and 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.

LROC NAC and WAC mosaic overlay showing a cross-section of Rima Hyginus at the point of the rock slide of interest, LROC QuickMap at 4 meters per pixel resolution [NASA/GSFC/Arizona State University].
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 here. 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.

Branch of Rima Hyginus trailing away east from the Hyginus crater, with the subject rock slide designated with the yellow arrow. Cropped at its full 52.5 meter resolution from LROC Wide Angle Camera monochrome (604nm) observation M177582468C, LRO orbit 11306, December 3, 2011, from 38.58 kilometers [NASA/GSFC/Arizona State University].
Examine more of Rima Hyginus in the full LROC NAC frame HERE.

Related Images:

Read more about the Hyginus region in the Icarus paper, "An igneous origin for Rima Hyginus and Hyginus crater on the Moon."

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