LROC: Rim on a rim (Hermann B)

A small fresh crater positioned right on the rim of Hermann B (0.35°S, 302.832°E). Material slides down the crater wall toward the crater center, creating small headscarps along the interior's rim. Image width is 650 m, LROC Narrow Angle Camera (NAC) observation M117867678RE, orbit 2503, January 11, 2010; field of view 650 meters from an original resolution of 0.68 meters per pixel from an altitude of 42.54 kilometers. See the 1000 x 1000 full size LROC Featured Image HERE  [NASA/GSFC/Arizona State University].

Drew Enns
LROC News System

Crater rims are a boundary between the inside and outside of a crater. Thus the rim is also where the slope changes from steeply down into a crater to the shallow sloping exterior.

This change in slope results in a ridge along which dry debris flows often form and carve backwards into the rim. This fresh crater is almost on top of the rim of Hermann B, so what does the whole crater look like?

A context image might give us an idea.

Context image for the Featured Image (white box), centered on 0.353°S, 302.830°E. The rim of the young crater is almost touching the rim of Hermann B. The interior of Hermann B is to the left with the exterior is to the right in this mosaic of the left and right frame pair for LROC NAC M117867678, subsampled to 2 meter/pixel. View the full size context image accompanying the Featured Image release HERE [NASA/GSFC/Arizona State University].

Full 3.4 kilometer width of the mosaic frame from the LROC Image Browser, providing context for the context image [NASA/GSFC/Arizona State University].

Amazingly, the small perched crater is not a simple bowl shape! Instead of having a discrete rim that rings the entire crater, the crater rim exists only along the upslope portion of Hermann B's crater wall. The other half of the crater rim is a mess! Boulders cover the center of the crater, and streamers were ejected downslope. The blocks hint that the bolide might not have been traveling very fast, and maybe it was a block of ejecta from another crater. Because the bolide that created the fresh crater may have been traveling relatively slowly when it impacted into Hermann B's sloped crater wall, the crater did not form a uniform shape!

Explore more of Hermann B's crater rim in the full NAC mosaic!

Related Posts:
Debris Flows in Gardner Crater
Boulder Mound
An Ill-defined Portion of an Otherwise Circular Rim

Stepping back still further, a 35 km-wide FOV of Hermann and Hermann B and the surrounding floor of Oceanus Procellarum, from a LROC Wide Angle Camera (WAC) observation (M150897433 - 643 nm) a little over one year after the Featured Image was swept up, in LRO orbit 7371, January 28, 2011; resolution is 58.8 meters per pixel from 42.27 km, early afternoon incidence angle 57.159° [NASA/GSFC/Arizona State University].