Teghaza 001: An ancient Martian gabbroic diorite derived from previously unsampled Martian crust and mantle

Martian meteorites provide key information about the geological history of Mars. However, our collection is biased by geologically young samples that are not representative of Mars’ exposed surface, which is dominated by ancient rocks. This generates gaps in our knowledge of Mars’ early evolution. Here, we report the discovery of a Martian meteorite, Teghaza 001, which is a gabbroic diorite with a minimum formation age of 4.1 Ga. The geochemistry, mineralogy, and 25 texture of Teghaza 001 are distinct from other Martian meteorites. Thus, Teghaza 001 represents previously unsampled ancient crust derived from a geochemically distinct mantle source. Alteration of minerals and elevated O isotopes suggest interactions with 18O-enriched fluids. This sample enhances our understanding of mantle heterogeneity and conditions in the crust on ancient Mars.