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Heterogenous Chemistry and The Possibility for Life in the Clouds of Venus

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The clouds of Venus are believed to be made of sulfuric acid (H2SO4), water (H2O) and other minor constituents. The chemical inventory in the clouds of Venus is unknown due to conflicting and extraordinary observations from several probes that have traveled through the clouds. X-Ray diffraction observations indicate that the clouds are formed primarily of the elements P, S, Cl and Fe, with roughly equal amounts of S and P. Mass spectrometry and chromatography indicate significant amounts of molecular oxygen (O2), methane (CH4), ethane (C2H6), hydrogen sulfide (H2S), phosphine (PH3) and ammonia (NH3) in the clouds, and detect water vapor at more than 1000 times the above-cloud and below-cloud measurements, and more than 100 times the spectroscopic observations of the probes themselves. Depletion of sulfur dioxide (SO2) above the clouds is well-supported by probes, satellite and ground-based observations, and cannot be explained solely by converting SO2 into H2SO4 and elemental sulfur. I will talk about three hypotheses that can explain the depletion of SO2 and some of the anomalous detections within the clouds: that there are hydroxide salts in the clouds (1), that there is life in the clouds converting N2 into NH3 (2), and that iron-sulfur chemistry is taking place in the cloud droplets (3). I will conclude by focusing on the “life in the clouds” hypothesis, and show that, if these chemical anomalies are signs of life, it is very different from terrestrial life, and its presence would pose a serious challenge for using disequilibrium biosignatures to search for life on other planets (4).


(1) Rimmer, P.B., Jordan, S., Constantinou, T., Woitke, P., Shorttle, O., Hobbs, R. and Paschodimas, A., 2021. Hydroxide salts in the clouds of Venus: Their effect on the sulfur cycle and cloud droplet pH. The Planetary Science Journal, 2(4), p.133.

(2) Bains, W., Petkowski, J.J., Rimmer, P.B. and Seager, S., 2021. Production of ammonia makes Venusian clouds habitable and explains observed cloud-level chemical anomalies. Proceedings of the National Academy of Sciences, 118(52), p.e2110889118.

(3) Jiang, C.Z., Rimmer, P.B., Lozano, G.G., Tosca, N.J., Kufner, C.L., Sasselov, D.D., Thompson, S.J. Iron-Sulfur Chemistry Can Explain the Ultraviolet Absorber in the Clouds of Venus. Submitted to Science Advances.

(4) Jordan, S., Shorttle, O. and Rimmer, P.B., 2022. Proposed energy-metabolisms cannot explain the atmospheric chemistry of Venus. Nature Communications, 13(1), p.3274.


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Topic: CAS SEMINAR : Prof Paul Rimmer Time: Feb 27, 2023 02:30 PM London

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This talk is part of the Centre for Atmospheric Science seminars, Chemistry Dept. series.

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