Venus may sparkle beautifully in the night sky, but up close, it is extremely inhospitable for life as it abounds of acid rains, has a CO2 atmosphere, and surface atmospheric pressure about 100 times greater than Earth‘s.
According to our understanding of life on our planet, Venus would be one of the last places in the Solar System to search for alien life. However, now, an international team of astronomers has detected something weird that might be a biosignature.
Traces of Life
On the other hand, it might be the sign of an abiotic chemical process that we have no information about. Or there might be some little-understood geological process taking place on this planet only. Either way, the finding is the harbinger of one massive learning experience.
Up in Venus’ dense clouds, where conditions are a bit more temperate and less damaging than the surface, scientists have identified signatures of phosphine gas, an element produced on Earth by both biotic and abiotic processes.
As per the team, the abiotic processes are improbable to have created the abundance of phosphine found in the planet’s cloud decks.
“I was stunned, frankly,” the study’s lead author and astrobiologist Jane Greaves of Cardiff University said. “[That abundance] suggests organisms – if working how they do on Earth – could be a sufficient source. They could only be at 10 percent of the peak efficiency in producing phosphine that we see from Earth organisms, and they would produce the abundance we see on Venus.”
Peculiar Acidic Clouds
What made the discovery even more curious is those acidic Venusian clouds, which would probably destroy phosphine rather quickly. Two findings, almost two years apart, suggest that whatever is creating the process is ongoing.
The next step in the study was to comprehensively analyze any other known process that can generate phosphine. On Saturn and Jupiter, phosphine, which is formed from one phosphorus and three hydrogen atoms, has been identified in rather massive quantities. It forms in the hot, high-pressure inner parts of the gas giants and is stirred out to the surface through convection.
However, for all its surface heat and pressure, Venus is not considered to match these phosphine formation settings, as found in the local gas giants. Other processes, such as lightning striking a phosphorus-carrying location, or phosphorus-bearing micrometeorites, could generate atmospheric phosphine, but the team discarded these mechanisms as well, as they are simply not rife on Venus to produce 20 ppb of phosphine.
“On Earth, we do have phosphine gas that comes from volcanic sources,” planetary scientist Helen Maynard-Casely of Australia’s Nuclear Science and Technology Organisation, who was not involved in the research, explained. “This is ruled out in this paper because they judge the amount of phosphine they observe could not be supported by volcanoes alone. I find this a little surprising, as there is abundant evidence for volcanic activity on Venus, much more than on Earth, plus we have much less of an idea of what the Venus surface is made out of.”
Greaves and colleagues have also pointed out that there might be an unknown chemical process leading the synthesis of phosphine on Venus. Considering the challenges of analyzing the planet up close, we don’t understand the surface that well, so unknown chemistry or geology processes are a rather strong possibility.
“It could suggest a whole reaction network we hadn’t discovered before, or abundance of, for example, phosphorus-bearing minerals that’s a lot different to Earth,” Greaves said.
Whatever is producing the phosphine traces in Venus’ atmosphere, finding the answer is definitely going to help us learn something new.
“It’s very hard to prove a negative. Now, astronomers will think of all the ways to justify phosphine without life, and I welcome that,” said molecular astrophysicist Clara Sousa-Silva of MIT. “Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine.”
A paper detailing the research has been published in Nature Astronomy.