Pseudotachylite as a possible sampling target for the Mars 2020 rover mission in Jezero crater, Mars.

From studies of large impact structures on Earth, a variety of different impactites, i.e., rocks that formed during a hypervelocity impact are known. A special impactite variety that can form during impact crater formation is the socalled pseudotachylite. These rocks are interpreted as the result of polyphase frictional melting and subsequent cooling that can take place on sliding surfaces during earthquakes, large landslides, and the tectonic collapse of impact structures; see, e.g., [1]. Pseudotachylites can occur as veins or dikelike outcrops in the central uplift or the crater wall, and comprise a microcrystalline or glassy matrix containing fragments of the wall rocks (see Fig. 1). The friction melt acts as a lubricant that allows the rocks to slip more easily along the fault plane during the modification stage of the craterforming process.