Evidence discovered that could indicate life on the most hostile planet in our solar system

Venus ranks among the most hostile places in the solar system, but astronomers have reported the discovery of two gases that could indicate life lurking in Venus' clouds.

The findings, presented at the National Astronomy Meeting in Hull on Wednesday, support evidence for a pungent gas, phosphine, whose presence on Venus has been hotly disputed.

A separate team reported a preliminary detection of ammonia, which on Earth is produced primarily by biological activity and industrial processes, and whose presence on Venus, the scientists said, cannot be easily explained by known atmospheric or geological phenomena.

The so-called biosignature gases are not conclusive evidence of extraterrestrial life, but the findings will heighten interest in Venus and raise the possibility that life emerged and even flourished in the planet's more temperate past and persists in the atmosphere today.

"Venus may have had a warm, wet period in the past, and with the onset of runaway greenhouse gases, life would have evolved to survive in the only place it could: the clouds," Dr Dave Clements, an astrophysicist at Imperial College London and one of the scientists involved in the study, told the meeting.

Venus' surface temperature is about 450 degrees Celsius, hot enough to melt lead and zinc, the atmospheric pressure is 90 times that of Earth's, and there are clouds of sulfuric acid. But about 50 kilometers (31 miles) above the surface, the temperature and pressure are closer to Earth's, and likely almost habitable for hardy microbes.

On Earth, phosphine is produced by microbes in oxygen-starved environments, such as badger guts and penguin poop. Other sources, such as volcanic activity, tend to be so inefficient that the gas is considered a sign of life on rocky planets.

The discovery of phosphine on Venus in 2020 was followed by controversy after subsequent observations failed to replicate the result. The latest observations by Clements and colleagues using the James Clerk Maxwell Telescope (JCMT), based in Hawaii, aim to resolve the dispute. By tracking the phosphine over time, they were able to strengthen the evidence for the gas’s presence, finding that its detection appears to follow the planet’s day-night cycle.

“Our results suggest that when the atmosphere is exposed to sunlight, phosphine is destroyed,” Clements explained. “All we can say is that phosphine is there. We don’t know what produces it. It could be chemistry we don’t understand. Or it could be life.”

Professor Jane Greaves, an astronomer at Cardiff University, revealed at the meeting preliminary observations from the Green Bank Telescope that point to ammonia, which is made on Earth either through industrial processes or by nitrogen-converting bacteria.

"Even if we confirm these two results, it's not proof that we've found these magical microbes and that they're living there today," Greaves said, adding that there are "no ground truths yet."

“These are very exciting discoveries but it should be stressed that the results are only preliminary and more work is needed to learn more about the presence of these two potential biomarkers in Venus’ clouds,” said Dr Robert Massey, Deputy Executive Director of the Royal Astronomical Society. “However, it is exciting to think that these discoveries could point to either potential signs of life or some unknown chemical process. It will be interesting to see what further investigations will uncover over the coming months and years.”