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?
Explore the boundary of mare basalts by viewing the full NAC frame!
Posted by Hiroyuki Sato on May 11, 2011 11:00.