Proposed Energy-metabolisms Cannot Explain The Atmospheric Chemistry Of Venus

By Keith Cowing
June 14, 2022
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Proposed Energy-metabolisms Cannot Explain The Atmospheric Chemistry Of Venus
Depletion contours of metabolic inputs. Contour plot showing depletion of metabolic reagents within the cloud layer for each metabolic pathway, (a), (b), and (c). Depletion is shown as a function of net metabolic rate (y-axis) and initial surface mixing ratio of the limiting metabolic reagent species (x-axis). The depletion of each species is calculated with respect to the species’ column abundance in a reference model run without the metabolism present. The predicted or observed surface mixing ratios of metabolic reagent species and their 1σ errors are indicated with grey errorbars,6 and the metabolic models reproducing SO2- depletion are indicated with a white dotted line.

Life in the clouds of Venus, if present in sufficiently high abundance, must be affecting the atmospheric chemistry. It has been proposed that abundant Venusian life could obtain energy from its environment using three possible sulfur energy-metabolisms.

These metabolisms raise the possibility of Venus’s enigmatic cloud-layer SO2-depletion being caused by life. We here couple each proposed energy-metabolism to a photochemical-kinetics code and self-consistently predict the composition of Venus’s atmosphere under the scenario that life produces the observed SO2-depletion.

Using this photo-bio-chemical kinetics code, we show that all three metabolisms can produce SO2-depletions, but do so by violating other observational constraints on Venus’s atmospheric chemistry.

We calculate the maximum possible biomass density of sulfur-metabolising life in the clouds, before violating observational constraints, to be ∼10−5−10−3mgm−3. The methods employed are equally applicable to aerial biospheres on Venus-like exoplanets, planets that are optimally poised for atmospheric characterisation in the near future.

Sean Jordan, Oliver Shorttle, Paul B. Rimmer

Comments: Published in Nature Communications
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2206.06414 [astro-ph.EP] (or arXiv:2206.06414v1 [astro-ph.EP] for this version)
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Submission history
From: Sean Jordan
[v1] Mon, 13 Jun 2022 18:47:46 UTC (128 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻