A Noachian hydrosphere component in the 4.1-Ga Martian meteorite Teghaza 001
2026-06-10
The recent discovery of a 4.1-billion-year-old (Ga) Martian gabbroic diorite enables an assessment of water reservoirs on early Mars. Measurements of H 2 O and D/H in igneous Ca-phosphates record mixing between D-poor magmatic water and a D-rich component that retains an imprint of the ancient Martian hydrosphere. The D/H ratio of magmatic water is similar in Martian magmas with different ages and mantle sources, indicating that early differentiation processes did not fractionate H isotopes in the primordial Martian mantle. The D-rich component was assimilated by migrating magmas that interacted with aqueously altered basaltic crust. Our minimum bound on the D/H ratio of the Martian hydrosphere at 4.1 Ga (~2× the D/H ratio of Earth seawater) supports models of rapid H loss to space from Mars’ juvenile atmosphere.