Downhill Creep or Flow?

Southern slope of a fracture developed in Vitello crater floor, downslope is toward upper left of the image. Image center is 30.214°S, 322.352°E, width is 640 m, LROC NAC M1101460425L [NASA/GSFC/Arizona State University]. 

Vitello crater is a floor-fractured crater (42.5 km in diameter), located at the south edge of Mare Humorum. As seen in the WAC context image, there is a circular network of fractures with numerous branches in the crater floor. The opening image highlights a portion of north facing slopes inside one of these fractures (yellow arrow).

The dark materials on the floor of the crater partially cover the upper part of this fracture. The dark materials extend from the bottom right to upper left and are detoured around of a large boulder (30 by 20 meters) at the center of opening image, indicating that these materials flowed down the slope. With occasional events of slope failures or meteorite impacts, they might have flowed at once or little by little over a long period of time. But of what is this dark material composed?

The origin of floor-fractured craters on the Moon is still under discussion, but volcanic intrusions are suspected, and some of the fractures are associated with Dark Mantle Deposits (DMD), that are likely pyroclastic in origin. In Vitello crater, no clear DMD have been documented. But since the circular cracks are well developed in this crater, pyroclastics or any low reflectance materials of volcanic origin might have covered the fractured floor surface, supplying the dark materials flowing into the open cracks as seen in the opening image.  

Vitello crater and surrounding areas in LROC WAC monochrome mosaic (100 m/pix). Image center is 30.43°S, 322.43°E. The locations of the opening image (yellow arrow) and the full NAC frame (blue box) are indicated [NASA/GSFC/Arizona State University].

Explore the slopes of the floor-fractured crater on the Moon in full NAC frame yourself! 

Related posts:

Rimae Posidonius, DMD Excavations, Pyroclastics and Vent, Pyroclastic Excavation, Pattern of dark deposits, Alphonsus crater mantled floor fracture, Low Reflectance Deposits on the Lassell Massif

Published by Hiroyuki Sato on 4 April 2013