The Influence of Interior Structure and Thermal State on Impact Melt Generation Upon Large Impacts Onto Terrestrial Planets

Kurzfassung

We use computer simulations to determine how planetary impacts cause melting, considering factors like planet size, impactor size, and core size. We find that larger planets experience more melting when struck by smaller impactors, while on smaller planets more melt is generated with larger impactors. This difference can be explained by the interplay of the temperature distribution inside the planet and its internal pressure, factors that control the amount of external energy needed to cause melting at a given depth. We usually find the largest melt volumes relative to the impactor volume on Earth-sized planets. The planet's core size does not strongly influence melting, except for very old planets with large cores, where melting decreases significantly. In order to estimate the total impact melt volume produced on a planet throughout its evolution, we combine the melt calculation findings with a planet-specific impactor flux function, which describes the size and frequency of impactors striking the planet over a given period of time. A Moon-sized planet accumulates the most melt relative to its size throughout its evolution. We also compare our results to simple melting approximations (“scaling laws”), which fail for melting events in complex planet structures and temperatures. Consequently, we propose a new way of predicting melting based on a planet's structure and age that is better suited for application to real planets than the scaling laws for homogeneous targets and should improve melt volume estimates in geological investigations without the need for an expensive and time-consuming numerical computation.