Whether or not there’s life on Venus is the subject of much debate among scientists, but a new study may close the case. Researchers at Cambridge have analyzed the Venusian atmosphere and found no sign of the chemical fingerprints microbes would be expected to produce – but it doesn’t rule out life on other similar planets.
At a glance, Venus seems pretty low on the list of likely places to find aliens. Temperatures on the surface soar as high as 464 °C (867 °F), which is hot enough to melt lead. The atmosphere is made up of 96 percent carbon dioxide, and the air pressure is as crushing as being 900 m (3,000 ft) under the sea on Earth.
However, it’s been proposed that microbial life could find refuge in the skies, at altitudes between 48 and 60 km (30 and 37 miles) where the temperatures and pressures are more Earth-like. Dark patches of clouds have been observed at this height, with optical signatures that look suspiciously like certain Earthly microbes that thrive on carbon dioxide and excrete sulfuric acid – both of which are common in Venus’ atmosphere.
To make matters more exciting, in 2020 astronomers reported the detection of phosphine in the planet’s atmosphere, a molecule that’s mostly known to be produced by anaerobic microbes and as such is considered a useful biosignature for life on other worlds. Sadly, a follow-up study found that the phosphine signal was likely a mistake, while another found that Venus has far too little water for even the hardiest of microbes.
The new study may hammer the final nail into the coffin. The team was examining a specific aspect of the hypothesis of life on Venus – namely, what’s sucking out sulfur dioxide (SO2) at higher altitudes? Life is a possible explanation, but it would produce other chemicals in the process, which would give away its presence.
The Cambridge researchers modeled three different possible metabolisms that could chew through so much SO2, and the resulting by-products they would emit, then compared that to the levels of those chemicals seen in Venus’ air. And sure enough, actual levels of all three expected by-products were much lower than would be given off by snacking microbes.
“If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus’s atmospheric chemistry,” said Sean Jordan, first author of the study. “We wanted life to be a potential explanation, but when we ran the models, it isn’t a viable solution. But if life isn’t responsible for what we see on Venus, it’s still a problem to be solved – there’s lots of strange chemistry to follow up on.”
It may be a bust for Venus, but the team says that the modeled metabolisms could still be applied to similar planets. Better yet, the sulfur molecules at the center of the method could be easily spotted in exoplanet atmospheres by the James Webb Space Telescope, which is due to start analyzing other worlds in a matter of months.
“Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could host life,” said Paul Rimmer, co-author of the study. “We can take what we’ve learned here and apply it to exoplanetary systems – this is just the beginning.”
The research was published in the journal Nature Communications.
Source: University of Cambridge
