Thursday, May 12, 2011

Pancakes in a melt pond

Pancake-like mound in Stevinus crater (33.03°S, 54.07°E). LROC Narrow Angle Camera observation M104162457R, LRO orbit 512, August 6, 2009; solar incidence 62°, field of view about 870 meters [NASA/GSFC/Arizona StLinkate University].

Hiroyuki Sato
LROC News System

The central peak of Stevinus crater is surrounded by a very flat and smooth floor. Small hummocks, fractures, and wrinkled textures all suggest that the flat and smooth floor is a frozen impact melt pond. However, small details in the floor show that the impact melt is not perfectly smooth. Just after the impact event, molten rocks and fragmented breccias were mixed together within the forming crater cavity. Think of a huge frying pan with this mix of molten and solid materials sloshing about. Slowly the melt solidified by surface cooling. If you look carefully you will find numerous pancake-like mounds on the smooth floor. What are they? Pancake mounds were likely created during the impact event, but the actual process is unknown. Did half solid, half molten rock lumps fall into the pond? Perhaps magma moving under the crust tried to push up and out of the crust as the crater floor readjusted? Or what if the pancake-like mounds were formed by slumping caused by small impacts over time?

LROC Wide Angle Camera Global 100 meter resolution monochrome mosaic of 77 km Stevinus. The blue rectangle and star indicate the location of entire NAC frame and the LROC Featured Image released May 11, 2011, respectively. View the full-sized LROC WAC context image HERE [NASA/GSFC/Arizona State University].

Explore the boundary of mare basalts by viewing the full NAC frame!

Related posts:
Mounds in a melt pond
Impact melt features in Tycho crater's floor
Anomalous mounds on the King crater floor

Simulated view courtesy of Google Moon showing the view, looking north from near the location of the LROC Featured Image of the Pancake Mound, south of Stevinus central peak. The north inner wall beyond towers nearly 5 kilometers higher in elevation above the crater's floor, 50 kilometers away.

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