Microbial life may be present in the atmosphere of Venus, according to a paper published in Nature Astronomy today.
(Written by Rohan Byrne, our resident geoscientist. Follow him at @buildmeaplanet)
Traces of a telltale gas called phosphine have been detected in sunlight bouncing off the planet. The gas, a rare chemical sometimes used as a pesticide, has never before been observed on rocky planets other than Earth, where it is almost always a product of life.
Because phosphine should deteriorate rapidly in Venus’s hyper-acidic atmosphere, whatever is producing it must still be active now. The planet is a hellish world of molten lead lashed by acid rain, but there is a layer of the atmosphere some 50 kilometres above the ground where air temperatures and pressures are comparable to those found on Earth. It is in this cloud belt that the gas was detected.
The abundance was greatest in the planet’s mid-latitudes, where exceptionally long-lived clouds might provide a tenuous habitat. Earlier this year, the discovery of active volcanoes on Venus drove speculation that nutrients from deep inside the planet may also be circulating in this part of the atmosphere, providing food for potential life.
The gas was observed using ground-based telescopes, including the James Clerk Maxwell observatory on Mauna Kea, Hawaii, the largest of its kind in the world. Researchers led by Professor Jane Greaves of Cardiff University, Wales, with colleagues from Cambridge University, MIT, and others observed the sunlight bouncing off Venus and broke it down into its spectrum – a rainbow pattern that can reveal the specific molecules making up a planet’s atmosphere.
They were able to extract the light signature of phosphine, which appears to make up about 20 parts per billion of the Venusian atmosphere. To make a similar proportion, Earth bacteria would need to operate at just 10% of their capacity.
After the initial discovery, an international team considered every alternative means of producing phosphine on Venus. They could find no other way to account for the volume except through living processes. If there proves to be no life on Venus after all, the discovery would up end our understanding of the chemistry of rocky planets.
If it is life, it is truly not as we know it. While airborne ecosystems do exist on Earth, they are always linked with land- or ocean-based systems. And while bacteria at home have been known to survive in extremely acidic environments, including toxic mining waste, the clouds on Venus are almost pure sulphuric acid with virtually no water at all: a more hostile environment than any on our planet.
The authors hope their findings will prompt a follow-up mission to what has been dubbed the ‘neglected planet’. One proposal is to deploy an acid-resistant blimp into the atmosphere, returning a gas sample – along with any potential critters – to the laboratory.