Led by postdoctoral researcher Nate Reed, Browne and an interdisciplinary team of scientists have now demonstrated that a slew of organosulfur molecules form when simple gas mixtures formulated to mimic the Archean Earth\u2019s atmosphere are exposed to UV light (Proc. Natl. Acad. Sci. U.S.A. 2025, DOI: 10.1073\/pnas.2516779122). Many are biologically relevant<\/a>.<\/p>\n \u201cWe didn’t have oxygen or ozone during this time period,\u201d Browne explains, so the gas mixtures contained nitrogen, methane, carbon dioxide, and hydrogen sulfide. After preparing gas mixtures, the researchers photolyzed the gases by exposing them to UV light from a deuterium lamp for a few minutes. And when the scientists caught and analyzed the resulting aerosols with two mass spectrometry techniques, they discovered small amounts of cysteine, homocysteine, methionine, coenzyme M, cysteine sulfinic acid, taurine, methyl sulfonic acid, and methyl sulfate.<\/p>\n \u201cThe reaction cell that we do [the experiments] in is the size of a small water bottle, so there’s not a lot of stuff that we make,\u201d Browne says. \u201cBut when you scale up a small water bottle to the size of the whole atmosphere, then you can start making a lot of these things.\u201d<\/p>\n In fact, the researchers estimate that 105\u20131010 moles of cysteine could have deposited onto early Earth every year as the haze of aerosols naturally fell from the sky. \u201cIt ends up being really competitive with other estimates of how some more-complex molecules could have been delivered to the surface,\u201d Browne says.<\/p>\n
\n Line structures of cysteine (left) and taurine (right)<\/p>\n
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