Sinuous Cracks

Northwestern rim of an unnamed crater located on southwest edge of Orientale basin. Image center is 22.110°S, 258.014°E, image width is 870 m. Downslope is to the lower-right. LROC NAC M184189330L [NASA/GSFC/Arizona State University].

Today's Featured Image highlights an upper portion of the crater wall of an unnamed crater (10.7 km diameter), located in the southwest portion of the Orientale basin. The rim crest is at upper-left of this image. The biggest crater at the left side is actually on the rim crest. 

The distinctive crack extending from the lower-left to upper-right cuts across a rough fractured slope. Most likely this surface corresponds to smoother terrain just outside the crater (upper left). Likely both surfaces formed as impact melt cooled. The portion on the steeper surface later fractured as gravity-driven slides slowly broke this crust.

Impact melts are recognized as common features on the Moon, the LROC NAC has imaged many spectacular occurrences (see links below). Impact melt deposits are of special interest to geologists as they hold a record of when an impact event occurred. A rocks radiometric clock starts ticking when it cools and hardens. If you can connect a particular impact melt rock to a crater, you can determine the exact time when the crater was formed.

The context view in LROC WAC monochrome mosaic (100 m/pixel). Image center is 21.95°S, 258.05°E, image width is about 86 km. The blue box and the yellow arrow indicate the locations of NAC footprint and today's Featured Image respectively [NASA/GSFC/Arizona State University].

Explore the sinuous cracks in the full NAC frame yourself!

Related posts:

Steps in Slipher SVeneer of MeltMelt on a RimImpact melt outside Wiener FCraggy Peak, Impact MeltsSlope failure near Aratus crater

Posted by Hiroyuki Sato on December 31, 2012 10:00 UTC.