Wednesday, October 10, 2012

Branched Impact Melts

Impact melt on the northern rim of an unnamed crater. Image center is 17.378°S, 85.205°E, image width is 500 m, downslope is towards the top. LROC Narrow Angle Camera (NAC) observation M139348293R, LRO orbit 6559, September 17, 2010; angle of incidence 20.25° at 0.5 meters resolution from 44.7 km  [NASA/GSFC/Arizona State University].
Hiroyuki Sato
LROC News System

Today's Featured Image highlights the viscous impact melt flow features found near an unnamed 4 km-wide crater centered near 17.247°S, 85.2°E, on the rim of crater Gibbs (78.8 km in diameter). You can see the low-reflectance viscous flow features forking into smaller terminal fingers.

These distinctive flows are found on the top of the older impact flows (older by seconds or minutes), and you can also see small channels formed as the molten rock flowed around blocks on the rim. These relations show us that this distinctive fingered flow was emplaced after most of the other ejecta. So how did this melt get to this location? One hypothesis is that this deposit of melted rock, along with all of the other ejecta produced by the impact that formed this crater, was expelled almost vertically. In this scenario, the melt that formed this deposit was then simply among the last to fall back to the surface, where it flowed around and over some of the ejecta that had fallen previously. Alternatively, this melt deposit could also simply be some of the last impact melt to be ejected from the crater during the last part of the excavation stage. No matter its exact origin, it is inspiring to see the tremendous forces of nature creating artistic patterns on our nearest neighbor.

The unnamed crater and surrounding area in LROC WAC monochrome mosaic (100 m/pix). The blue box and yellow allow indicate the location of full NAC frame and today's Featured Image respectively. Image center is 17.25ºS, 85.20ºE [NASA/GSFC/Arizona State University].

Explore this fork-shaped impact melt deposit in full NAC frame yourself, HERE.

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Impact Melt Fingers
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