Abstract

The clouds of Venus have been proposed as a potential abode for life. Life, if present in sufficiently high abundance, must be interacting with the atmospheric chemistry via its metabolism. Three possible sulfur-based metabolisms have been previously suggested which Venusian life could use to obtain energy from its environment. These metabolisms raise the possibility of Venus’s enigmatic cloud-layer SO2 -depletion being caused by life. We perform a test for the possiblity of abundant Venusian life by coupling each proposed energy-metabolism to a photochemical-kinetics code and predicting the composition of Venus’s atmosphere under the scenario that life produces the observed SO2 -depletion. Using this coupled 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 therefore calculate an upper limit on the possible biomass of sulfur-metabolising life in the clouds of Venus before violating observational constraints.