The Evolution of Regolith
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Transregional Collaborative Research
Center TRR 170: Late Accretion onto Terrestrial Planets
Impact events are widespread over the lunar surface. One of the most prominent features of the impact process is the melted target rock resulting from the high postshock temperatures. Such melted rocks as the relic of the historical impacts can be used to investigate the late heavy bombardment hypothesis, and thus the further understanding of the early evolution of the terrestrial planets.
The purpose of the work is to understand the long-term effect of the impact gardening process on the presence of impact melt of different ages at the near-surface of the Moon. It is possible to make reasonable estimates of the amount of melt produced by impact events of differing scales, and likewise the depth of excavation and the quantity of unheated material which is redistributed at the surface. However, the cumulative effect of a long sequence of impacts melting, excavating, burying and reexcavating material produces a megaregolith which is complex in its melt distribution with depth.
Current computational capabilities make it feasible to simulate regolith accumulation and displacement by a Monte Carlo model, and thus to build a picture of the time evolution of the regolith with depth. At the same time, by tracking the creation and presence of melt, we can understand how it is mixed into the regolith, and what abundances of melt with different ages could be expected in surface samples. Comparing the simulation results with the age-dating results basin on the lunar samples, the knowledge of lunar impact history will be improved. This aspect is very much tied to our previous work, where we studied crater formation rates and concentrated on refining the crater-dating method.