The Royal Astronomical Society has announced a potentially groundbreaking discovery: astronomers have detected phosphine gas in Venus' clouds—a molecule produced on Earth by anaerobic bacteria.
Venus, once considered Earth's twin, is now the solar system's most inhospitable world. Surface temperatures average 462°C—hot enough to melt lead—with atmospheric pressure 92 times Earth's. Higher up, clouds of sulfur dioxide and sulfuric acid create a corrosive environment seemingly hostile to life. Yet, intriguing evidence suggests otherwise.
In a press conference on Monday, researchers from the Royal Astronomical Society in London revealed the spectral signature of phosphine at altitudes with Earth-like temperatures and pressures. First spotted in 2017 using the James Clerk Maxwell Telescope, it was confirmed in 2019 with the Atacama Large Millimeter/Submillimeter Array (ALMA).
On Earth, phosphine is produced synthetically as a pesticide or by oxygen-free extremophile microbes. It's been found in hydrogen-rich atmospheres like Jupiter and Saturn, but this marks the first detection on a rocky planet besides Earth.
“When we got the first hints of phosphine in Venus' spectrum, it was a shock,” said lead researcher Jane Greaves of Cardiff University, who spearheaded the discovery. Venus' atmosphere should oxidize phosphine, yet telescopes measured up to 20 ppm.
These consistent detections, years apart, point to an ongoing phosphine source on our "evil twin." The key question: what produces it?
On gas giants like Jupiter and Saturn, phosphine forms deep in hot, high-pressure interiors and rises via convection. Venus lacks such conditions. Publishing in Nature Astronomy, the team ruled out 40 non-biological sources—sunlight, minerals, volcanoes, lightning—finding they could produce, at most, one-tenth the observed levels.
While unknown chemistry isn't dismissed, the researchers favor a biological origin. Earth extremophiles could generate it at just 10% capacity in Venus' clouds.
Emmanuel Marcq, lecturer at Versailles-Saint Quentin University, called it a "particularly interesting" find in a France Inter interview, urging infrared confirmation: "We must verify with infrared observations, where gases show unique signatures, to eliminate doubt."
If chemistry fails to explain it, he notes, "we'll consider biological production—extremophile life in Venus' cloud droplets."
The Cardiff team urges further study, including new probes for direct sampling and Earth return.
