Sulfur chemistry in the middle atmosphere of Venus

Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds

“…This likely has contributed to the redistribution of volatile mass, as the larger number of potential activation sites results in a more even distribution of mass, hence smaller and more numerous droplets. Another consequence of this is that the larger number of cloud droplets overall results in a larger number of droplets able to reach higher altitude via eddy diffusion in our model, possibly providing a source for observed enhancements of sulfuric acid vapor at high altitudes (Zhang et al 2012). As to the question of why this should occur only at mid-latitudes, the answer at this point would be mere speculation.…”

Elemental sulfur aerosol-forming mechanism

“…•• H 2 S reaction occurs in a low-energy manner and is strongly exothermic. Note that the SO 2 mixing ratio in the middle atmosphere is the highest among the sulfur gases (17,18) implying that the SO 2 + H 2 SO 4…”

“…The thermal reactions of SO 3 and SO with H 2 SO 4 •• H 2 S clearly explain this anticorrelation. These thermal reactions not only provide useful mechanistic insights into an important sink of sulfur gases below 90 km in the Venus atmosphere, but may also help in understanding the mixing profiles of SO and SO 2 at higher altitudes (1,17,18,(32)(33)(34)(35)(36). At 96-km Venus atmosphere, the rates of the SO 3 hydration and the SO 3 photolysis are found to be comparable (17), which is suggestive of the fact that nearly half of the sulfur in H 2 SO 4 goes into SO 3 and produces the inversion layers of SO 2 and SO.…”

“…One of the most important sources of sulfur into the atmosphere is from volcanoes, and the most abundant sulfur gases are SO 2 and H 2 S. The photochemistry of these gases in the atmosphere yields elemental sulfur, sulfur particles, sulfuric acid, and oceanic sulfate. Scheme 1 illustrates the chemical processes suggested to be important in the photochemical oxidation of volcanic sulfur species in the early atmosphere of Earth.The S 0 aerosols are not only involved in the Archean life, but are also implicated in other environments (1,(11)(12)(13)(14)(15)(16)(17)(18)(19). For example, polysulfur (S x = S 2→8 ) aerosols are thought to exist in clouds of Venus and their role as the unknown UV absorber in its lower atmosphere has been discussed in the literature (14).…”

“…The S 0 aerosols are not only involved in the Archean life, but are also implicated in other environments (1,(11)(12)(13)(14)(15)(16)(17)(18)(19). For example, polysulfur (S x = S 2→8 ) aerosols are thought to exist in clouds of Venus and their role as the unknown UV absorber in its lower atmosphere has been discussed in the literature (14).…”