Phosphine gas has been detected in the atmosphere of Venus, according to a paper published in Nature Astronomy. This finding suggests that Venus could host unknown photochemical or geochemical processes.
On Earth, phosphine is a gas that is produced predominantly by anaerobic biological sources. The conditions at the surface of Venus are hostile to life, but the environment of its upper cloud deck — around 53–62 km above the surface — is temperate. However, the make-up of the clouds is highly acidic, and in such conditions phosphine would be destroyed very quickly.
Jane Greaves and colleagues observed Venus with the James Clerk Maxwell Telescope and the Atacama Large Millimeter/submillimeter Array in 2017 and 2019, respectively. They detected a spectral signature that is unique to phosphine, and estimated an abundance of 20 parts-per-billion of phosphine in Venus’s clouds. The authors investigated different ways the phosphine may have been produced, including from sources on the surface of the planet, micrometeorites, lightning, or chemical processes happening within the clouds. Ultimately, they were unable to determine the source of the trace quantities of phosphine.
The authors argue that the detection of phosphine is not robust evidence for microbial life and only indicates potentially unknown geological or chemical processes occurring on Venus. Further observations and modelling are needed to explore the origin of phosphine in Venus’s atmosphere.
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