A Martian meteorite that formed ≳4.1 billion years ago samples Mars’ early crust and mantle
Yang Liu, Lee M. Saper, Elizabeth Ann Bell, Chi Ma, Haoyu Li, Jinping Hu, Yunbin Guan, Hayward Melton, Alicia M. Cruz-Uribe, Teng Ee Yap, François L.H. Tissot, Claire E. Bucholz, Karen Ziegler, Carl B. AgeeMartian meteorites provide a record of the planet’s geological history. However, most are geologically young samples that are not representative of Mars’ surface, which is dominated by ancient rocks. We describe the Martian meteorite Teghaza 001 (Teg 001), a slowly cooled igneous rock that formed at least 4.1 billion years ago. Its composition, mineralogy, and texture are distinct from other Martian meteorites. We determine that Teg 001 is a sample of ancient crust, which formed from a geochemically distinct mantle source with primordial composition. The presence of aqueously altered minerals, combined with bulk and mineral-specific oxygen isotope measurements, indicate that Teg 001 experienced reactions with fluids enriched in 18 O, before ejection into space by an impact.