Melt or Rubble?

The bottom of northern crater wall inside Carrel crater, downslope is toward the bottom. Image center is 10.846°N, 26.653°E, image width is 500 meters, incidence angle is about 69°, LROC NAC M177460712L [NASA/GSFC/Arizona State University]. 

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 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. 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. 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.  

Carrel crater and the surrounding area in LROC WAC monochrome mosaic (100 m/pix). Image center is 10.65°N, 26.71°E. The locations of full NAC frame (blue box) and the opening image (yellow arrow) are shown here [NASA/GSFC/Arizona State University]. 

Explore these beautiful and enigmatic flow features in full NAC frame yourself!

Related posts:

Debris Flows in Kepler Crater, How Recent?, Meandering, Pytheas, Detour!, Outside of Giordano Bruno, Dichotomy, Dry debris or liquid flow?, Granular Flow, Rock avalanche in Robinson crater

Published by Hiroyuki Sato on 2 April 2013