| Summary: | The heat source for partial melting of the mare basalt source region is believed to be the urKREEP layer at the base of the crust. An initially spherically symmetric Moon model, hot or cold, allowed to evolve by axisymmetric convection inside a spherical shell for 300--600 Myr, is impacted by a large thermal anomaly, representing South Pole-Aitken basin, or a small thermal anomaly, representing Imbrium basin, and is then observed for 100 Myr of evolution. The energy of the large impact (South Pole-Aitken) is enough to remove the urKREEP layer from beneath the ejecta blanket by mantle circulation and is interpreted as the removal of the heat source for partial melting of a shallow mare basalt source region and explains the absence of fill in the basin while a small impact (Imbrium) cannot produce enough mantle circulation in the time allotted to remove the layer of heat producing elements from the basin surroundings.
|
|---|