Lunar Reconnaissance Orbiter Camera

Slump or Slide

Rock and debris slumped from northwest to southeast (upper left to center) and cascaded into the floor of a linear topographic low (depression or graben) near Milichius crater; arrows indicate the direction of movement. NAC M190794864L; image width 1.2 km; illuminated from east; downslope toward center of image [NASA/GSFC/Arizona State University].

A linear topographic low (a depression or graben) located southeast of Milichius crater (330.646°E, 9.342°N) shows tell-tale signs of mass wasting, the ongoing process of erosion that levels out surface topography (see figure below). A large mass movement, more than 1 kilometer across, eroded part of the depression wall near its southwest end (see opening image). Unlike the example of mass wasting highlighted in Tuesday's Featured Image of Schubert A crater, which resulted from many small individual rock movements, this material likely moved as one large unit. Was this the result of a landslide or of a slump? Understanding how landforms erode tell us about their properties including angle of bedding planes, composition (such as rock or soil), and mechanical properties such as shear strength (the ability to resist downslope movement).

WAC context image of the region southeast of Milichius crater. A linear negative-relief feature (or depression) that is a local topographic low cuts across the center of the area. Yellow box shows the location of today's Featured Image near the southwest end of the depression [NASA/GSFC/Arizona State University].

Landslides involve rock and debris moving downslope along a planar surface, whereas slumping usually occurs along a curved interface and as a single large unit. Slumps are commonly observed in large impact craters, including Giordano Bruno, Darwin C, Klute W, Milne N, and Steno Q. The example near Milichius crater, however, does not occur in a large impact crater. Yet, the segmented arcuate faults near the head of the material (upper left of opening image) are similar to those of slumped materials in impact craters. Arrows point toward the end of the material, or toe, where rock and debris has come to rest in the floor of the narrow (roughly 1.5 km wide) linear depression. High-resolution NAC stereo imagery of this area would be useful in order to better constrain the morphology of this material and allow us to better differentiate between a landslide or a slump.

Explore the full NAC image to look for more landslides in this area!

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