Abstract:
The possible effects of large, late impacts on magma genesis on the moon are analyzed. The amount of heat required to melt solidified residual liquids and late cumulates in the lunar crust is calculated for various conditions, and compared to estimates of the kinetic energy of the Imbrium impact. It is shown that impact energies on the order of the maximum estimated for Imbrium or the Gargantuan impact would be necessary to alter significantly the compositional options of magma genesis at depth. Observational data supplied by orbital X-ray and gamma-ray measurements, photogeology, and analysis of lunar samples is then related to thermal models of magma genesis and various large impacts. It is concluded that large late impacts such as Imbrium or larger, earlier impacts such as Gargantuan may have had effects on magma genesis and volcanism and affected the range of chemical compositions of mare basalts, depending on the timing of the impact with respect to the heat engine of the moon.
