Wednesday, February 6, 2013

Debris Flows in Kepler Crater

The lower part of the northeast wall of nearside landmark crater Kepler. Loose material is sliding down from near the rim crest (upper right) and ponding on a part of the crater floor. LROC Narrow Angle Camera (NAC) M104755664L, LRO orbit 595, August 12, 2009; resolution 1.27 meters from 119.86 km [NASA/GSFC/Arizona State University].
Jeffrey Plescia
LROC News System

The Featured Image shows the lower slopes of the northeast inner wall of the Kepler impact crater (8.1°N, 322.0°E, diameter 32 km). Loose material often moves down the steep slopes of impact craters, and there are many examples of lunar landslides. The observation that such landslides exist on the Moon were first made during the Apollo program using the images taken from the Command Module while it was in lunar orbit.

This landslide is composed of a range of particle sizes from well below the pixel scale (1.25 m/pixel) to boulders as large as 20 m. Debris slid down the walls and spread out across the crater floor being locally deflected by obstacles on the crater floor. The crater wall has a slope of about 33°.

Another similar pond at the bottom of a long granular debris flow, this one on the southeast wall and floor of Kepler but captured two years later, and at a high resolution opportunity afforded by spacecraft maneuvers in late summer 2011.  LROC NAC M168455361R, LRO orbit 9959, August 20, 2011; 29 cm per pixel, at 36.67° angle of incidence from 22.92 km [NASA/GSFC/Arizona State University].
In the center left of the (top) image, a coarse debris flow was diverted around local topography into several narrow (up to 12 meters wide) flows that extend an additional 400-500 m across the slope and crater floor. Boulders accumulated at the base of the debris flows after rolling all the way down the slope. Debris flows occurred numerous times in this location, as well as many other locations around the crater wall. The material acted as a fluid as it moved downslope flowing around and over obstacles and ponding behind obstructions despite the fact that there was no water present.

View of the northeast crater wall of Kepler, the field of view in the LROC Featured Image outlined by the white box. Legend: F: crater floor, FB: fault block which has slide down the crater wall, CR: crater rim. LROC NAC M104755664L [NASA/GSFC/Arizona State University].
Above is a reduced resolution version of a larger area around the image shown above (outlined by the white box). Several bright debris flows are observed along the inner crater wall. The area around Kepler crater is illustrated in the wide angle image below.

Kepler Crater (32 km diameter) and surrounding plains, afternoon lighting. LRO Wide Angle Camera (WAC) M117738837M. [NASA/GSFC/Arizona State University].
View the entire LROC NAC frame, HERE.

Oblique view of Kepler from on-board Apollo 12, November 1969; 70mm B/W, AS12-52-5547 [NASA/JSC/LPI].
In the shadow of Copernicus, Kepler's bright, widely distributed ejecta and rays would more easily stand out to the naked eye if the similarly youthful and larger crater to its east did not exist. From one of the incredible telescopic mosaics, this one of a Full Moon, by Yuri Goryachko and ASTRONOMINSK team, March 29, 2010.
 Related Posts:

How Recent?
Granular Flow
Debris Channels
Kepler's Rim

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