Are Atmospheric Anomalies on Venus Signs of Life?

The atmosphere of Venus has long puzzled astronomers and planetary scientists. Since the 1920s, observers of Venus have noted strong atmospheric absorption in the near-ultraviolet spectrum and, despite a wide variety of proposed explanations, none is universally accepted today. Soviet and U.S. atmospheric probes have reported detecting trace amounts of methane and oxygen, neither of which should be stable in the chemical environment of the Venusian atmosphere, along with particulate matter which remains unidentified. More recently, spectral evidence for the presence of phosphine gas has been reported by researchers including Dr Janusz Petkowski of the MIT department of Earth, Atmospheric, and Planetary Science, interviewed here. Phosphine is considered a “biomarker” when found on Earth, and no persuasive abiotic source is known on Venus. Could the atmosphere of Venus, where conditions are no more exotic than those on Earth where “extremophile” bacteria thrive, be home to an extraterrestrial biosphere?

An earlier post here discussed transfer of microbes from Venus to Earth via the solar wind during inferior conjunctions and transits of Venus.