Detection of phosphine gas in Venus' atmosphere hints at life

An international team of scientists and researchers recently announced "spectral detections" of phosphine (PH3 – a phosphorus atom with three hydrogen atoms attached), a potential sign of life in the clouds high above the surface of Venus. 

The discovery was made by a team led by Jane Greaves from Cardiff University and the University of Cambridge in the United Kingdom, along with Clara Sousa-Silva who has done groundbreaking work with phosphine. The transitions were first observed with the James Clerk Maxwell Telescope (JCMT) in Hawaii and then confirmed by Sousa-Silva using the ALMA radio telescope in Chile. The stinky gas, which is highly toxic to humans, was found at 20 parts per billion – a teaspoon in an Olympic-size pool – in the upper atmosphere of Venus, about 30-60 miles above the broiling surface. 

Researchers indicated that the presence of the gas "could originate from unknown photochemistry or geochemistry, or [on] Earth from the presence of life." Other potential sources of PH3 on Venus were ruled out, including lightning, volcanic activity and even meteors.

Out in the solar system, phosphine is found in abundance on the larger gaseous planets such as Jupiter and Saturn. Under immense pressure in the lower atmosphere, the gas giants smash phosphorus and hydrogen atoms together, but smaller rocky planets like Earth and Venus must produce the gas via other means.

On Earth, phosphine can be made industrially for nefarious purposes, as a chemical weapon or fumigants. Walter White infamously used it as an impromptu weapon on the TV show "Breaking Bad." It can also be found in sewage or other oxygen-starved environments, perhaps as a byproduct of anaerobic life or microbial organisms, but its production isn't clearly understood. 

Sarah Stewart Johnson, planetary scientist and head of the Johnson Biosignatures Lab at Georgetown University (not involved in the work), told The New York Times that, “There’s been a lot of buzz about phosphine as a biosignature gas for exoplanets recently. How cool to find it on Venus.”

One of the brightest objects in the night sky, Venus has not been a high priority in the search for life. Instead, financial and technological resources have been pointed at Mars, with future missions looking at the moons of Europa, Titan and Ganymede where the evidence of liquid water is mounting. Venus, however, is a veritable hell-scape – reaching temperatures of over 800 degrees Fahrenheit, and producing surface level pressure that would feel like being 3,000 feet under the ocean. The planet's clouds are suffused with sulfuric acid. 

Previous missions to the planet surface did not last long as Venus both eats metal and crushes it under its immense pressure. Currently, the Japanese probe Akatsuki is the sole spaceship orbiting the planet. 

Within the upper atmosphere, however, where the clouds are a stable 86 degrees and the pressure comparable to Earth's, hardy microbes might be able to survive the sulfuric environment. 

"If no known chemical process can explain PH3 within the upper atmosphere of Venus," the researchers wrote in Nature, "then it must be produced by a process not previously considered plausible for Venusian conditions. This could be unknown photochemistry or geochemistry, or possibly life."

The team stressed caution in jumping to conclusions, however, and said that the detection of phosphine is not a clear-cut indication of life. It said further study is required to understand what is creating the gas in the clouds of Venus. 

NASA Administrator Jim Bridenstine, wrote on Twitter, saying, "Life on Venus? The discovery of phosphine, a byproduct of anaerobic biology, is the most significant development yet in building the case for life off Earth. It’s time to prioritize Venus."

Only further observations of Venus, possibly in the form of return missions, will determine whether the Venusian atmosphere is teaming with extraterrestrial life.