Tuesday, April 2, 2013

Melt or Rubble in Carrel Crater?

Debris pile at the bottom of north wall of Carrel crater (downslope toward bottom). Image center near 10.846°N, 26.653°E, field of view 500 meters, incidence angle is about 69° LROC Narrow Angle Camera (NAC) observation M177460712L, spacecraft orbit 11288, December 2, 2011; native resolution 47 cm per pixel from 38.78 km [NASA/GSFC/Arizona State University].
Hiroyuki Sato
LROC News System

Carrel crater (15.6 km in diameter) is located near the center of Mare Tranquillitatis.

On the north wall of this crater you can find several eye-catching flow features, starting from near the top of the wall, merged together on the way down to the bottom and finally deposited in a local topographic depression.

 The opening image highlights the infilled depression.

Is this fill composed of solidified impact melt, or simply a granular flow that originated by a slope failure? Which do you think?

The 4640 meter full width of the left and right frames of LROC NAC M177460712, from the newly-revised LROC QuickMap, zeroed in on Carrel crater. The feature highlighted in above and another, similar phenomena are designated with arrows [NASA/GSFC/Arizona State University].
The large incidence angle (69°, measured from vertical) of this image shows distinct relief of these flow features. The materials dumped in the depression show a flat surface where half is covered by gravel or rubble. The shadows along the left edge of this deposit give depth and imply a certain thickness, and no cracks or ridges are recognizable on the deposit surface. Typically impact melt flows exhibit viscous flow features (e.g. round distal edges, pressure ridges and levees as seen in Necho Crater, Channels And Fractures, Lichtenberg B Flow) and surface cracks. Not all these features are found in today's Featured Image.

Carrel crater and vicinity in LROC Wide Angle Camera (WAC) monochrome mosaic (100 m/pix), centered near 10.65°N, 26.71°E. The locations of full NAC frame (blue box) and the featured highlighted in the LROC Featured Image, released April 2, 2013 (yellow arrow) are shown [NASA/GSFC/Arizona State University].
Granular flows normally spread out in the final deposit, making thin distal edges as seen in Detour!, Debris Flows in Kepler Crater, Pytheas. But like these examples (Granular Flow, Outside of Giordano Bruno, How Recent?), sometimes they form thick round shapes or have levees along the flow path.

Carrel, a landmark crater of a First Quarter Moon, almost exactly between the landing site of Apollo 11, northwest of Moltke at bottom center and Apollo 17 in Taurus Littrow valley, just west of top center. Astronominsk April 21, 2010.
Those are rather similar to the features observed in the opening image, implying that these flows and the deposit might be formed by granular flows, but it is not easy to conclude due to its enigmatic shape. 

Explore these beautiful and enigmatic flow features in full NAC frame yourself, HERE.

Related Posts:
Debris Flows in Kepler Crater
How Recent?
Outside of Giordano Bruno
Dry debris or liquid flow?
Granular Flow
Rock avalanche in Robinson crater

No comments: