Hypervelocity Impacts on Ancient Martian Distinct Clays

An experimental study is presented aimed at understanding the formation and morphology of impact craters on Mars, with particular emphasis on the role of hydrated and stratified materials representative of conditions similar to those of the Noachian period. The Martian hemispheric dichotomy and the possible past existence of liquid water suggest that factors such as transient layers, clay deposits, and salts significantly influenced crater evolution and the preservation of geological and mineralogical evidence [1].

To simulate hypervelocity impacts, a two-stage light gas gun at the University of Kent [2] was used to accelerate 2 mm aluminium spheres to velocities between 2 and 5 km s^-1 toward clay targets with different configurations: variations in water content, iron (III) oxide content, and surface layers with differing degrees of hydration or salinity. 8 shots with unique target material composition were conducted, allowing analysis of the relationship between impact velocity, target composition, and the resulting crater geometry.

The results show that, in general, crater depth follows expected trends based on the degree of material hydration, with less hydrated clays producing deeper craters. Contrary to initial predictions, a deviation was observed by the formation of deeper and wider craters in the presence of a surface salt layer. Additionally, the inclusion of iron increased crater dimensions. These findings suggest that the compositional and stratigraphic heterogeneity of the Martian subsurface plays a key role in impact processes, affecting both crater morphology and the preservation of records of water and potential biosignatures. This study contributes to a better interpretation of Mars’ geological history and highlights the importance of using realistic analogue materials in laboratory experiments.

[1] Anderson et al., 2022, Icarus; [2] Hibbert et al., 2017, Procedia Engineering.