Impact Melt Lobes

Impact melt flowed down the 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 NAC M184196652RE, sun is from the upper left and image width is 1000m [NASA/GSFC/Arizona State University].

A marked up version of today's Featured Image. The black arrows point to the first flow boundaries and the white arrows point to where the second flow has been channelized. LROC NAC M184196652RE, image width is 1000 m [NASA/GSFC/Arizona State University].

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 located at  at 12.922° S, 256.525° E. Today's Featured Image is located at the red arrow. Image width 100 km [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 in the full LROC NAC!

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Published by Drew Enns on 12 April 2012