Space Weathering-Induced Formation of Hydrogen Sulfide (H2S) and Hydrogen Disulfide (H2S2) in the Murchison Meteorite

Theoretical calculations and experimental simulations indicate that the surprisingly low sulfur abundance on the surfaces of spacecraft visited S-type asteroids 433 Eros and 25143 Itokawa may be due to space weathering. Two current missions, Osiris-Rex and Hayabusa 2, are studing asteroids 101955 Bennu (B-type) and 162173 Ryugu (C-type), respectively. Understanding space weathering effects related to sulfur containing species is only in the beginning stages and has not been studied from the point of view of C-type asteroids. This laboratory study details the formation of hydrogen sulfide (H2S) and hydrogen disulfide (H2S2) from conversion of nonvolatile-sulfuretted species in the Murchison meteorite by exposure to energetic electrons and laser processing, which mimics the synergic effect of secondary electrons generated by galactic cosmic rays and high-energy solar wind particles plus micrometeorite impact on airless bodies. The results indicate that space weathering processes likely induce depletion of sulfur on the surface of C-type and undifferentiated S-type asteroids. For keeping scientific integrity of these fragile species, cold/cryogenic curation of future collected samples from asteroids might be required.