On The Biomass Required To Produce Phosphine Detected In The Cloud Decks Of Venus

TL;DR

This paper evaluates whether biological processes could produce the observed phosphine levels in Venus's clouds, finding that the required biomass might be feasible and discussing potential sampling methods.

Contribution

It introduces a simple model estimating biomass needed for phosphine production on Venus, suggesting it could be within plausible ranges and exploring spacecraft sampling strategies.

Findings

Biomass estimates are potentially much lower than Earth's aerial biosphere.

The observed phosphine flux could be produced by a feasible biomass density.

Small spacecraft could effectively sample Venus's cloud decks for biomarkers.

Abstract

The detection of phosphine in the atmosphere of Venus at an abundance of $\sim 20$ ppb suggests that this gas is being generated by either indeterminate abiotic pathways or biological processes. We consider the latter possibility, and explore whether the amount of biomass required to produce the observed flux of phosphine may be reasonable. We estimate that the typical biomass densities predicted by our simple model are potentially orders of magnitude lower than the biomass density of Earth's aerial biosphere in the lower atmosphere. We briefly discuss how small spacecraft could sample the Venusian cloud decks and search for biomarkers.