Traces of phosphine gas detected in the clouds above Venus could be an indication that the planet supports microbial life, a study has concluded.
On Earth, phosphine, a colorless gas that smells like garlic or decaying fish, is naturally produced mainly by certain microorganisms in the absence of oxygen. It can also be released in small amounts from the breakdown of organic matter, or industrially synthesized in chemical plants.
Experts from the UK, however, found signs of phosphine in Venus’ atmosphere, suggesting the planet must support unknown chemical process, or even life.
The second-closest planet to the sun, Venus is inhospitable, with a surface temperature around 867°F (464°C) and pressure 92 times that of on the Earth. However, its upper cloud deck 33-38 miles above the surface, is a more temperate 120°F (50°C), with a pressure equal to that at Earth sea level.
The clouds are also highly acidic, meaning that the phosphine would be broken down very quickly and must therefore be being continually replenished. The researchers have cautioned, however, that life is only one possible explanation for the source of the phosphine, with further investigation needed.
NASA is presently considering two missions to Venus that propose to study the planet’s atmosphere and geochemistry, dubbed “DAVINCI” and “VERITAS”.
In their study, astronomer Jane Greaves of Wales’ Cardiff University and colleagues observed Venus using both the James Clerk Maxwell Telescope at Hawaii’s Mauna Kea Observatory and the Atacama Large Millimeter/submillimeter Array in Chile.
They detected a so-called spectral signature that is unique to phosphine and were able to estimate that the gas is present in Venus’ clouds in an abundance of around 20 parts-per-billion.
The team explored assorted ways that the gas could have been produced in this setting, including from sources on the surface of the planet, micrometeorites, lightning, or chemical processes happening within the clouds themselves. However, they were unable to determine exactly what is the source of the detected trace quantities of gas.
The researchers have cautioned that the detection of phosphine is not itself robust evidence of alien microbial live, and only indicates that potentially unknown geological or chemical processes are occurring on the plant.
Further observations and modeling will be needed to better explore the origin of the gas in the planet’s atmosphere.
“Phosphine could originate from unknown photochemistry or geochemistry, or by analogy with biological production of phosphine on Earth, from the presence of life,” the research team wrote in their paper. “If no known chemical process can explain phosphine with the upper atmosphere of Venus, 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.”