New observational evidence of global seismic effects of basin-forming impacts on the Moon from Lunar Reconnaissance Orbiter Lunar Orbiter Laser Altimeter data



[1] New maps of kilometer-scale topographic roughness and concavity of the Moon reveal a very distinctive roughness signature of the proximal ejecta deposits of the Orientale basin (the Hevelius Formation). No other lunar impact basin, even the just-preceding Imbrium basin, is characterized by this type of signature although most have similar types of ejecta units and secondary crater structures. The preservation of this distinctive signature, and its lack in basins formed prior to Orientale, is interpreted to be the result of seismically induced smoothing caused by this latest major basin-forming event. Intense seismic waves accompanying the Orientale basin-forming event preceded the emplacement of its ejecta in time and operated to shake and smooth steep and rough topography associated with earlier basin deposits such as Imbrium. Orientale ejecta emplaced immediately following the passage of the seismic waves formed the distinctive roughness signature that has been preserved for almost 4 billion years.