Swept Surface inside Nicholson crater

A portion of the floor of Nicholson crater on the mountainous rings surrounding Mare Orientale, is swept away by the pressure front delivered by a smaller and much more recent impact. From LROC Narrow Angle Camera (NAC) observation M140468128R, centered on 26.103°S, 274.952°E; 612 meter wide field of view captured at 51 cm resolution during LRO orbit 5834, September 30, 2010 [NASA/GSFC/Arizona State University].

Hiroyuki Sato
LROC News System

The opening image is of a surface swept by the ejecta of an unnamed 300 meter diameter fresh crater that is located about 1.8 km to the south. This area is on the floor of Nicholson crater (about 38 km in diameter), that is at the southeast edge of Orientale basin.

As you can see in the next NAC context image, the higher reflectance rays extending radially outward from the parent crater highlight the path of ejecta. But the actual area of the continuous ejecta deposition is difficult to detect from the reflectance contrasts alone. When a single ejecta particle hits it churns up the subsurface revealing brighter immature material from below.

A wider, approximately 1.7 km view of the opening field of view (white box) shows the young unnamed crater on Nicholson crater's floor immediately to the south [NASA/GSFC/Arizona State University].

Among the numerous rays, high reflectance spots can be found at the north side of multiple small craters (~40 m in diameters). Some appear to be pre-existing craters that had their rims eroded by the ejecta, thus revealing brighter immature material. The small craters with very bright ejecta may be the result of large blocks of ejecta that were thrown out at a shallow angle and plowed up the substrate also revealing immature material.

Dramatic context for Nicholson crater, situated on the peak ring mountains, second row out from the interior basin of Mare Orientale, is seen in this false color orthographic projection of the LROC Wide Angle Camera Digital Terrain Model, centered on the 300th meridian east [NASA/GSFC/DLR/Arizona State University].

The overall effect of low angle ejecta spraying across the surface is similar to blowing dust on the Earth that erodes the landscape. Of course the Moon has no atmosphere, so the sand blasting effect lasts for a mere seconds rather the slow cumulative effect of wind-blown dust on the Earth. 

Explore the newly disturbed surface on the Moon in full NAC frame yourself, HERE.

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