Pre-Accretion Formation of Sulfuric Acid in Interstellar Ice Analogs: Implications for Sulfate in Ryugu and Bennu

[The Journal of Physical Chemistry Letters] Sulfate-bearing phases and soluble sulfate species, including sodium sulfate (Na₂SO₄), in carbonaceous asteroids are commonly attributed to parent-body aqueous alteration, yet the formation of S(+VI) sulfate under the reducing, low-temperature conditions inferred for primitive bodies remains chemically challenging.

Here, we show that sulfuric acid (H₂SO₄ ) can form before accretion through irradiation of sulfur dioxide/water (SO₂/H₂O) interstellar ice analogs at 5 K. Threshold photoionization, deuterium labeling, and sulfur isotope analysis unambiguously identify sulfuric acid, establishing a route from preaccretion ice chemistry to oxidized sulfur reservoirs.

If incorporated into accreting planetesimals, such preaccretion H₂SO₄ could subsequently be mobilized, neutralized, and precipitated during aqueous alteration, providing a potential contribution to sulfate-bearing phases in primitive carbonaceous bodies.

• Pre-Accretion Formation of Sulfuric Acid in Interstellar Ice Analogs: Implications for Sulfate in Ryugu and Bennu, The Journal of Physical Chemistry Letters via PubMed
• Pre-Accretion Formation of Sulfuric Acid in Interstellar Ice Analogs: Implications for Sulfate in Ryugu and Bennu, The Journal of Physical Chemistry Letters (open access)

Astrobiology, Astrochemistry,