Did life exist on Venus in the past?
Because liquid water is the key to life as we know it, if Venus had water on its surface for billions of years it’s possible that microbial life emerged during that time. We don’t know for sure, though, and looking for evidence of past life on Venus is almost impossible with current technologies.
Although orbiters can teach us a lot about a planet, to search for signs of past life we need to take a much closer look. On Mars, we look for past microbial life by sending rovers like Curiosity and Perseverance to analyze rock samples. But Venus is a much more difficult place to explore on the surface. Only a handful of landers have successfully operated on the Venusian surface. Many more have tried and failed, but even the successful missions were only able to operate for hours at most before being destroyed by the planet’s extreme conditions. This doesn’t give spacecraft enough time to do things like collect and analyze rock samples to look for microscopic fossils.
Does life exist on Venus now?
Although life as we know it is almost certainly impossible in the harsh conditions on the surface of Venus, it’s possible that it could survive in the Venusian atmosphere. Although Venus’ lower atmosphere contains toxic clouds of sulfuric acid, at higher levels the conditions are much less deadly.
In 2020 scientists announced they found phosphine gas — a potential biosignature, i.e. a chemical strongly associated with biological processes — in Venus’ clouds 50 kilometers (roughly 31 miles) above the surface, where temperatures and pressures are much more Earth-like. Phosphine’s presence has since been disputed, then later reclaimed but with an alternative explanation for its origins, disputed once again, and redetected lower in the atmosphere. The verdict on whether phosphine exists in the clouds of Venus, and whether its presence would mean there were life forms producing it, is still very much undecided.