Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH
The depletion of SO _2 and H _2 O in and above the clouds of Venus (45–65 km) cannot be explained by known gas-phase chemistry and the observed composition of the atmosphere. We apply a full-atmosphere model of Venus to investigate three potential explanations for the SO _2 and H _2 O depletion: (1)...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2021-01-01
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| Series: | The Planetary Science Journal |
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| Online Access: | https://doi.org/10.3847/PSJ/ac0156 |
| _version_ | 1797361825857142784 |
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| author | Paul B. Rimmer Sean Jordan Tereza Constantinou Peter Woitke Oliver Shorttle Richard Hobbs Alessia Paschodimas |
| author_facet | Paul B. Rimmer Sean Jordan Tereza Constantinou Peter Woitke Oliver Shorttle Richard Hobbs Alessia Paschodimas |
| author_sort | Paul B. Rimmer |
| collection | DOAJ |
| description | The depletion of SO _2 and H _2 O in and above the clouds of Venus (45–65 km) cannot be explained by known gas-phase chemistry and the observed composition of the atmosphere. We apply a full-atmosphere model of Venus to investigate three potential explanations for the SO _2 and H _2 O depletion: (1) varying the below-cloud water vapor (H _2 O), (2) varying the below-cloud sulfur dioxide (SO _2 ), and (3) the incorporation of chemical reactions inside the sulfuric acid cloud droplets. We find that increasing the below-cloud H _2 O to explain the SO _2 depletion results in a cloud top that is 20 km too high, above-cloud O _2 three orders of magnitude greater than observational upper limits, and no SO above 80 km. The SO _2 depletion can be explained by decreasing the below-cloud SO _2 to 20 ppm. The depletion of SO _2 in the clouds can also be explained by the SO _2 dissolving into the clouds, if the droplets contain hydroxide salts. These salts buffer the cloud pH. The amount of salts sufficient to explain the SO _2 depletion entails a droplet pH of ∼1 at 50 km. Because sulfuric acid is constantly condensing out into the cloud droplets, there must be a continuous and pervasive flux of salts of ≈10 ^−13 mol cm ^−2 s ^−1 driving the cloud droplet chemistry. An atmospheric probe can test both of these explanations by measuring the pH of the cloud droplets and the concentrations of gas-phase SO _2 below the clouds. |
| first_indexed | 2024-03-08T15:58:58Z |
| format | Article |
| id | doaj.art-dee8d1273b084aefa133f7b3cb0d163c |
| institution | Directory Open Access Journal |
| issn | 2632-3338 |
| language | English |
| last_indexed | 2024-03-08T15:58:58Z |
| publishDate | 2021-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Planetary Science Journal |
| spelling | doaj.art-dee8d1273b084aefa133f7b3cb0d163c2024-01-08T14:13:39ZengIOP PublishingThe Planetary Science Journal2632-33382021-01-012413310.3847/PSJ/ac0156Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pHPaul B. Rimmer0https://orcid.org/0000-0002-7180-081XSean Jordan1Tereza Constantinou2Peter Woitke3Oliver Shorttle4https://orcid.org/0000-0002-8713-1446Richard Hobbs5Alessia Paschodimas6Department of Earth Sciences, University of Cambridge , Downing Street, Cambridge CB2 3EQ, UK ; pbr27@cam.ac.uk; Cavendish Laboratory, University of Cambridge , JJ Thomson Avenue, Cambridge CB3 0HE, UK; MRC Laboratory of Molecular Biology , Francis Crick Avenue, Cambridge CB2 0QH, UKInstitute of Astronomy, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UKInstitute of Astronomy, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UKSUPA, School of Physics & Astronomy, University of St Andrews , St Andrews KY16 9SS, UK; Centre for Exoplanet Science, University of St Andrews , St Andrews, UKDepartment of Earth Sciences, University of Cambridge , Downing Street, Cambridge CB2 3EQ, UK ; pbr27@cam.ac.uk; Institute of Astronomy, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UKInstitute of Astronomy, University of Cambridge , Madingley Road, Cambridge CB3 0HA, UKCentre for Exoplanet Science, University of St Andrews , St Andrews, UK; Earth and Environmental Sciences, University of St Andrews , Irvine Building, North Street, St Andrews, KY16 9AL, UKThe depletion of SO _2 and H _2 O in and above the clouds of Venus (45–65 km) cannot be explained by known gas-phase chemistry and the observed composition of the atmosphere. We apply a full-atmosphere model of Venus to investigate three potential explanations for the SO _2 and H _2 O depletion: (1) varying the below-cloud water vapor (H _2 O), (2) varying the below-cloud sulfur dioxide (SO _2 ), and (3) the incorporation of chemical reactions inside the sulfuric acid cloud droplets. We find that increasing the below-cloud H _2 O to explain the SO _2 depletion results in a cloud top that is 20 km too high, above-cloud O _2 three orders of magnitude greater than observational upper limits, and no SO above 80 km. The SO _2 depletion can be explained by decreasing the below-cloud SO _2 to 20 ppm. The depletion of SO _2 in the clouds can also be explained by the SO _2 dissolving into the clouds, if the droplets contain hydroxide salts. These salts buffer the cloud pH. The amount of salts sufficient to explain the SO _2 depletion entails a droplet pH of ∼1 at 50 km. Because sulfuric acid is constantly condensing out into the cloud droplets, there must be a continuous and pervasive flux of salts of ≈10 ^−13 mol cm ^−2 s ^−1 driving the cloud droplet chemistry. An atmospheric probe can test both of these explanations by measuring the pH of the cloud droplets and the concentrations of gas-phase SO _2 below the clouds.https://doi.org/10.3847/PSJ/ac0156VenusPlanetary atmospheresWater vaporClouds |
| spellingShingle | Paul B. Rimmer Sean Jordan Tereza Constantinou Peter Woitke Oliver Shorttle Richard Hobbs Alessia Paschodimas Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH The Planetary Science Journal Venus Planetary atmospheres Water vapor Clouds |
| title | Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH |
| title_full | Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH |
| title_fullStr | Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH |
| title_full_unstemmed | Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH |
| title_short | Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH |
| title_sort | hydroxide salts in the clouds of venus their effect on the sulfur cycle and cloud droplet ph |
| topic | Venus Planetary atmospheres Water vapor Clouds |
| url | https://doi.org/10.3847/PSJ/ac0156 |
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