2021/01/21 by Paul B. Rimmer, Seán F. Jordan, Rimmer, Paul B. +11
Engineering · Physics and Astronomy · #Astro and Planetary Science #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Planetary Science and Exploration #Space Exploration and Technology
paper · pdf · doi:10.48550/arxiv.2101.08582
openalex publication_date 2021/01/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The depletion of SO2 and H2O in and above the clouds of Venus (45 -- 65\nkm) cannot be explained by known gas-phase chemistry and the observed\ncomposition of the atmosphere. We apply a full-atmosphere model of Venus to\ninvestigate three potential explanations for the SO2 and H2O depletion:\n(1) varying the below-cloud water vapor (H2O), (2) varying the below-cloud\nsulfur dioxide (SO2), and (3) the incorporation of chemical reactions inside\nthe sulfuric acid cloud droplets. We find that increasing the below-cloud\nH2O to explain the SO2 depletion results in a cloud top that is 20 km too\nhigh, above-cloud O2 three orders of magnitude greater than observational\nupper limits and no SO above 80 km. The SO2 depletion can be explained by\ndecreasing the below-cloud SO2 to 20 , rm ppm. The depletion of SO2\nin the clouds can also be explained by the SO2 dissolving into the clouds,\nif the droplets contain hydroxide salts. These salts buffer the cloud pH. The\namount of salts sufficient to explain the SO2 depletion entail a droplet pH\nof \∼ 1 at 50 km. Since sulfuric acid is constantly condensing out into the\ncloud droplets, there must be a continuous and pervasive flux of salts of\n\≈ 10-13 , rm mol , cm-2 , s-1 driving the cloud droplet\nchemistry. An atmospheric probe can test both of these explanations by\nmeasuring the pH of the cloud droplets and the concentrations of gas-phase\nSO2 below the clouds.\n