Thursday, August 23, 2012

Twin pools in small Southern Highlands crater

Two small melt flows solidified on the wall of a young crater, and melt pooled in its center. situated on the broad floor of the crater Orontius, in the bright southern highlands immediately east of Tycho. LROC Narrow Angle Camera (NAC) M188270580RE, LRO orbit 12806, April 5, 2012. Image field of view is 700 meters. See the larger original LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Drew Enns
LROC News System

Impact melt commonly forms during impact events on the Moon due to the tremendous energy released during such events.

Melt often forms ponds on crater floors or in nearby exterior depressions, and forms flows as it travels downslope. Today's Featured Image of a young crater in the lunar highlands, at 40.875°S, 355.277°E, appears to have beautifully preserved examples of both forms!

Can we be sure the flows pointed out here are actually frozen impact melt and not debris flows?

LROC Wide Angle Camera (WAC) global mosaic overlaying LOLA topography shows the small bright crater, surrounded by a very bright landscape in the vicinity of Tycho, inside the west wall of Orontius at lower center. View the original LROC WAC context image accompanying the LROC Featured Image released August 21, 2012 HERE [NASA/LMMP/GSFC/Arizona State University].
One clue is that the flows are not very blocky when most of the crater wall is. Instead the flows appear to have entrained rocks when traveling over blocky sections of the crater. But debris flows can also pick up boulders along the way! Unlike the melt pond the flows do not have a cracked surface, perhaps indicating that formed as flows of granular material? On the other hand the flows have lower reflectance, typically of glasses that form on the surface of impact melt. It is difficult to say which hypothesis is correct without more information!

Can you find more evidence to argue for impact melt or debris flow in the full LROC NAC frame HERE?

Related Posts:
River of Rock
Crater in 3D!

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