Elemental sulfur aerosol-forming mechanism.

Kumar, Manoj; Francisco, Joseph S · Proc Natl Acad Sci U S A · 2017

basic_science · Level V

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Abstract

Elemental sulfur aerosols are ubiquitous in the atmospheres of Venus, ancient Earth, and Mars. There is now an evolving body of evidence suggesting that these aerosols have also played a role in the evolution of early life on Earth. However, the exact details of their formation mechanism remain an open question. The present theoretical calculations suggest a chemical mechanism that takes advantage of the interaction between sulfur oxides, SO<sub>n</sub> (n = 1, 2, 3) and hydrogen sulfide (nH<sub>2</sub>S), resulting in the efficient formation of a S<sub>n+1</sub> particle. Interestingly, the SO<sub>n</sub> + nH<sub>2</sub>S → S<sub>n+1</sub> + nH<sub>2</sub>O reactions occur via low-energy pathways under water or sulfuric acid catalysis. Once the S<sub>n+1</sub> particles are formed, they may further nucleate to form larger polysulfur aerosols, thus providing a chemical framework for understanding the formation mechanism of S<sup>0</sup> aerosols in different environments.