Fractures and boulders on the floor of De Forest

Fractured impact melt left the interior of De Forest crater (56.25 km; 76.94°S, 196.67°E) lined with boulders. 665 meter-wide field of view from LROC NAC observation M125650563L, 665 meter-wide field of view from LRO orbit 3650, April 11, 2010; 78.87° incidence angle, resolution 57 cm from 55.16 km over 77.1°S, 197.94°E [NASA/GSFC/Arizona State University].

Hiroyuki Sato

LROC News System

Today's Featured Image highlights a portion of the interior of De Forest crater (56.25 km; 76.94°S, 196.67°E), which is located inside the South Pole–Aitken basin.

The cavity of De Forest crater exhibits prominent terraces of collapsed materials surrounding the central peak (see context imagery following).

The topographic low, east of the central peak, was largely coated with hot impact melt which formed a hard crust as it cooled; a portion of this melt is seen in the opening image. 

Context view of De Forest crater (56.25 km; 76.94°S, 196.67°E) consisting of LROC WAC monochrome mosaic (100 m/pix) overlain with colorized WAC stereo DTM (GLD100, Scholten et al., 2012). View centered on 76.92°S, 197.51°E. Footprint of LROC NAC observation M125650563L, April 11, 2010, outlined in blue, source of high-resolution view of the area designated with a yellow arrow (LROC Featured Image released August 5, 2014) [NASA/GSFC/Arizona State University]. 

Much of the area of the opening image is covered by numerous boulders, some of which are up to approximately 15 meters across.

The smooth surface extending in lower-left to upper-right is impact melt that cooled to form solid rock, and is now fractured in regular patterns along the edge. Impact melt that was splashed on the crater's walls and its central peak formed a coating that quickly cooled to solid rock.

On the true "backside" of the Moon, De Forest (right) is situated well inside South Pole-Aitken impact basin, between Antoniadi (upper left, near horizon), host of the Moon's lowest elevation (-9094 meters) and Shackleton (not pictured), host of the Moon's south pole. HDTV still from Japan's lunar orbiter Kaguya (SELENE-1) in 2008 [JAXA/NHK/SELENE].

Later, it is likely that nearby moonquakes caused these brittle rock coatings to fracture, providing the source of boulders we now see on the lower reaches of the crater floor.

De Forest's position in the far south Farside is an area hosting Permanently Shadowed Regions (PSR's). The neutron detection experiment on-board LRO (LEND) has built up signatures consistent with cold-trapped volatiles, like water ice, in the vicinity. Image from Science Visualization Studio tour of SPA, larger image HERE [NASA/GSFC/Arizona State University/DLR/SVS]. 

As you can see in the following full NAC frame, an enormous number of similar boulders are found along the smooth melt deposits on the floor of De Forest crater. 

Explore this boulder-rich crater in the full NAC frame, HERE.

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