Friday, September 30, 2011

LROC: Farside Impact!

A young, fresh impact into the farside highlands, south of Tsiolkovskiy crater. LROC Narrow Angle Camera (NAC) observation M159073200L, LRO orbit 8576, May 3, 2011; image field of view is roughly 325 meters wide. See the full size LROC Featured Image HERE [NASA/GSFC/Arizona State University].
Lillian Ostrach
LROC News System

Young impacts abound on the Moon, and the LROC NAC images of beautiful crater morphologies, spectacular ejecta blankets, and stunning impact melt deposits are enough to make any lunar geologist jump for joy. Many times, fresh impacts into mare material are featured because these craters punch through the thin layer of regolith and produce boulders. However, impacts into the lunar highlands can be just as spectacular.

Today's Featured Image of an unnamed Copernican-aged crater (~630 m diameter, 29.73°S, 134.07°E) is one such example on the farside. Close-up, the crater is bowl-shaped with a well-defined circular rim. At the crater floor center is a small, bouldery pond of solidified impact melt. Debris from the crater walls have slumped toward the floor center, but whether these slumps happened immediately after crater formation or yesterday is difficult to determine. 

The first in a brief series of reduced views of a relatively small fresh impact crater near the southwestern rim of the far more ancient 61 km-wide crater Subbotin, in the Farside lunar Highlands [NASA/GSFC/Arizona State University].
Take a look at some of the material nearest to the crater floor; in the crater center, some slumps are veneered with impact melt but other debris piles superpose (overlie) these veneered materials. These stratigraphic relationships can be used to interpret the relative ages of the slumps - the impact melt-covered piles formed soon after impact because they are splashed with impact melt, and the overlying debris piles happened after the impact melt solidified (maybe even yesterday!). Furthermore, the ejecta blanket closest to the crater rim is mostly uniform in reflectance but there are scatterings of boulders and lower-reflectance impact melt streamers that were thrown out of the crater during ejecta emplacement. 

What a beauty! 

A further reduced-resolution view from M159073200L, showing a 2.7 km field of view. See the full-size LROC context image HERE [NASA/GSFC/Arizona State University].
LROC WAC monochrome (566nm) mosaic of the Farside west of Subbotin crater swept up over the course of LRO orbits 4924 through 4926, July 20, 2010. The fresh impact crater in the opening image the small "bulls eye" just left of center in the image above. At this illumination incidence angle, ~72.7° from the west north west, the deeper central circular floor of the crater is already deeply shadowed in the coming sunset.  [NASA/GSFC/Arizona State University].
What other exciting geologic features do you observe when you explore the full LROC NAC image?

Related Posts:
Small crater at the southern rim of Menelaus
Smooth floor in Copernicus crater

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