Elemental sulfur aerosol-forming mechanism.

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 (n = 1, 2, 3) and hydrogen sulfide (nHS), resulting in the efficient formation of a S particle. Interestingly, the SO + nHS → S + nHO reactions occur via low-energy pathways under water or sulfuric acid catalysis. Once the S particles are formed, they may further nucleate to form larger polysulfur aerosols, thus providing a chemical framework for understanding the formation mechanism of S aerosols in different environments.