Thursday, February 28, 2013

Lobate debris aprons on the Moon?

Debris flows mantle the wall of an unnamed farside southern highlands crater east of Pavlov (30.63°S, 145.66°E). LROC Narrow Angle Camera (NAC) frame M176684041L, spacecraft orbit 11173, November 23, 2011; illumination angle of incidence 63.77° from the east, 0.51 meters resolution from 48.32 km [NASA/GSFC/Arizona State University].
James Ashley
LROC News System

Similar in appearance to some lobate debris aprons on Mars, these deposits are found at the base of a craggy escarpment where cascading rock and dust has accumulated in an unusual pattern. Irregularities in the outcrop topography channeled and funneled the debris as it moved over them, producing overlapping mounds which were themselves sculpted by subsequent debris flow.

Theories used to explain the rounded or "softened" appearance of similar features on Mars often involve the lubrication or "creep" activity of buried ice deposits. This cannot be the case on the Moon, of course, which is depleted of water and other volatile substances. While ice may be involved in many of the Mars aprons, features such as these serve to caution the student of planetary science to consider all possible modes of origin when exploring new terrains.

Zoom-out on the NAC frame reveals similar features running the length of the escarpment; an approximate 2.4 km wide field of view. (Area with the LROC Featured Image released February 28, 2013 is within the yellow box) [NASA/GSFC/Arizona State University].

Zoom out further to the field of view in a mosaic of both the left and right frames (M176684041LR. Area within the context image immediately above is in the yellow frame.) [NASA/GSFC/Arizona State University].
A high-angle view of the unnamed crater, with the area of interest marked with an arrow, shows the extensive and bright ray structure super-positioned on older features, like Jules Verne Y to the southeast. Chang'e-2 global 60 meter mosaic [CNSA/CLEP].
LROC Wide Angle Camera (WAC) 100 meter global monochrome mosaic, a field of view roughly 120 km across [NASA/GSFC/Arizona State University].
Explore the full NAC image HERE.

Additional features collected from the same region can be viewed at LROC Featured Image posts like Pile Up, and Scours and Ejecta Near Jules Verne Y. Additionally, examples of debris flow features can be viewed at Debris Flows in Kepler Crater, Rock Slide in Rima Hyginus, and Multiple Flow Lobes.

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