Sign of Alien Life May Have Been Found in the Clouds of Venus, Scientists Say

Astronomers have detected a rare molecule known as phosphine in the clouds of Venus, which could potentially be a signature of alien life, they say.

While the scientists stress that the identification of phosphine gas in the atmosphere of our planetary neighbor is far from concrete proof that microbial life exists there, this is one possible explanation for their findings.

In their research, the international team detected a spectral signature unique to phosphine in the clouds of Venus in observations of the planet conducted by the James Clerk Maxwell Telescope (JCMT) in Hawaii in 2017, according to a study published in the journal Nature Astronomy.

Two years later, they followed up these observations with a survey conducted by the Atacama Large Millimeter/submillimeter Array in Chile.

"When we got the first hints of phosphine in Venus' spectrum, it was a shock!" Jane Greaves, lead author of the study from Cardiff University, U.K., who first spotted signs of the molecule in observations conducted by the James Clerk Maxwell Telescope (JCMT) in Hawaii, said in a statement.

"In the end, we found that both observatories had seen the same thing—faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below," Greaves said.

After the discovery of phosphine traces in Venus' atmosphere, the scientists tried to work out how the gas could have been produced using computer modeling techniques. They investigated various natural processes, including micrometeorites, volcanoes, lightning, sunlight, minerals being blown upwards from the surface and chemical processes occurring in the clouds.

But none of these known processes could account for the amount of phosphine that the scientists had observed and were consequently ruled out. Because the clouds where the phosphine was detected are highly acidic, the gas should be destroyed very quickly. The fact that it is still present in the quantities observed suggests something is continuously generating it.

According to the authors, the only remaining possibilities that could account for the phosphine are "aerial" microbes in the atmosphere that could be producing it. If this is not the case, some unknown geological or chemical processes must be present that we would not expect to find on a rocky planet like Venus.

On our own planet, there are only two main sources of phosphine gas: industry and microbes that inhabit extreme oxygen-free environments.

While much of Venus appears to be totally inhospitable to life with its scorching hot surface temperatures and its atmosphere filled with thick clouds of sulfuric acid, there are parts of the atmosphere—between 30-40 miles above the surface—where conditions are temperate, and both sunlight and water are present, though the clouds are still highly acidic there.

Some other scientists have speculated, controversially, that if life existed on Venus, this would be the only place where it could survive.

"This phosphine signal is perfectly positioned where others have conjectured the area could be habitable," co-author of the study Janusz Petkowski from Massachusetts Institute of Technology said in a statement.

The authors note that any microbial life that potentially exists in this region would have to be very different to anything we know about on Earth, and confirming its presence there would require much more research.

The latest findings have been greeted with excitement by other scientists in the field of astronomy, although many also note that the research is not conclusive proof that life exists on Venus.

"This is one of the most exciting signs of the possible presence of life beyond Earth I have ever seen, and certainly from the most surprising location I could imagine! Our twin planet Venus is a hellish world," Alan Duffy, an astronomer from Swinburne University, Australia, who was not involved in the research, said in a statement.

"While the temperature is benign in the clouds [they] contain sulfuric acid which should break down the phosphine, so something is forming it anew, and as phosphine is associated with life on Earth it is tempting to think it could be life on Venus but before we can become more confident about that we have to rule out all possible other non-biological means of producing it. This paper was exhaustive in ruling out the possibilities, but there may yet be non-living chemical pathways in the extreme environment on Venus that we haven't yet discovered."

According to Duffy, detecting life on Venus will require confirmation in a lab, which could mean that "NASA's long-dreamed of mission to Venus" with gigantic balloons floating in the upper atmosphere may finally come to fruition.

Brendan Burns, a researcher at the School of Biotechnology and Biomolecular Sciences at The University of New South Wales and Deputy Director of the Australian Centre for Astrobiology, who was also not involved in the research, described the results as "intriguing" but urged caution about interpreting the findings.

"This finding comes with a huge caveat: the atmosphere of Venus is 96 percent carbon dioxide, with a surface temperature of up to 460 degrees Celsius [860 degrees Fahrenheit] making it the hottest planet in our solar system. In addition to the high CO2 there are also clouds of sulfuric acid so these are conditions not exactly welcoming to life—as we know it," he said in a statement.

"Far more work is needed to follow up these observations, but even a slim possibility of a biosignature of life existing outside Earth has the profound potential to alter our understanding of our very place in the universe."

This article was updated to include additional comments from Alan Duffy and Brendan Burns.