Thursday, April 12, 2012

LROC: Impact Melt Lobes

Impact melt flowed back down inside the east wall of Lowell crater forming two lobes when it solidified. The first lobe was breached or overtopped by a second flow in a manner probably similar to lava flows on Earth. LROC Narrow Angle Camera (NAC) image M184196652RE, LRO orbit 12236, February 18, 2012; resolution 1 meter per pixel with the later afternoon sun is from the northwest. Image field of view is 1000 meters. View the full-size LROC Featured Image HERE [NASA/GSFC/Arizona State University].
A marked up version of the full-width NAC image from which the LROC Featured Image was cropped (white frame). The black arrows point to the first flow boundaries and white arrows to where a second flow was channelized. [NASA/GSFC/Arizona State University].
Drew Enns
LROC News System

Today's Featured Image is a beautiful example of a viscous flow on the Moon. What appears to be one large flow that traveled down Lowell crater's wall is, upon further inspection, two distinct lobes!

A section of the first lobe was breached or overrun by a second flow, allowing the flow to progress further.

If it was caused by a breach, this might be similar to how pahoehoe lava flows on Earth inflate and break out to expand. Several other impact melt flows show similar relations, but in most cases impact melt flows with morphologies like this occur exterior to craters. 

So why is this flow inside a crater?

Context image of Lowell crater, 12.922° S, 256.525° E. The LROC Featured Image is focused on the area designated by the red arrow. Lowell crater's official diameter is 62.6 kilometers. View the larger LROC context image accompanying the release, HERE [NASA/GSFC/Arizona State University].
Looking at the WAC context image, there is a small crater on the edge of Lowell crater. This smaller crater might be the source of the impact melt! If so, this particular impact melt flow wasn't generated in the same impact event that created Lowell crater. Instead a later impact occurred on Lowell's rim and melt flowed back into Lowell crater. But the overlapping flows indicate there must have been two pulses of melt flowing downward. Perhaps during the impact an initial glob of impact melt was thrown downslope and then quickly followed by a second flow!

Explore more of the impact melt in Lowell crater's interior by viewing the full length of full LROC NAC image, HERE.

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