Newswise – The unusual behavior of sulfur in Venus’ atmosphere cannot be explained by an “aerial” form of extraterrestrial life, according to a new study.
Researchers at Cambridge University used a combination of biochemistry and atmospheric chemistry to test the “cloud life” hypothesis that astronomers have been speculating on for decades, and found that life cannot explain the composition of the cloud. Venusian atmosphere.
Any life form in sufficient abundance is expected to leave chemical fingerprints in a planet’s atmosphere as it consumes food and expels waste. However, Cambridge researchers found no evidence of these fingerprints on Venus.
Even if Venus is not alive, researchers say its results, published in the journal Nature Communications, could be useful for studying the atmospheres of galaxy-like planets and the eventual detection of life outside our Solar System.
“We’ve spent the last two years trying to explain the strange chemistry of sulfur we see in the clouds of Venus,” the co-author said. Dr. Paul Rimmer of the Cambridge Department of Earth Sciences. “Life is pretty good with weird chemistry, so we’ve been studying if there’s a way to make life a possible explanation for what we see.”
The researchers used a combination of atmospheric and biochemical models to study the chemical reactions that are expected to occur, given the known sources of chemical energy in Venus’ atmosphere.
“We analyzed the sulfur-based ‘food’ available in the Venusian atmosphere; it’s nothing you or I would want to eat, but it’s the main source of energy available,” he said. Sean Jordan of the Cambridge Institute for Astronomy, the first author of the paper. “If life consumes this food, we should see evidence of this through specific chemicals that are lost and gained in the atmosphere.”
The models analyzed a particular feature of the Venusian atmosphere: the abundance of sulfur dioxide (SO2). On Earth, most SO2 in the atmosphere comes from volcanic emissions. On Venus, there are high levels of SO2 lower in the clouds, but it is somehow “sucked” from the atmosphere at higher altitudes.
“If there is life, it must be affecting atmospheric chemistry,” the co-author said Dr. Oliver Shorttle from the Department of Earth Sciences and the Cambridge Institute for Astronomy. “Could life be the reason why SO2 levels on Venus are dropping so much?”
The models, developed by Jordan, include a list of metabolic reactions that would be carried out by life forms in order to get their “food” and waste by-products. The researchers ran the model to see if the reduction in SO2 levels could be explained by these metabolic reactions.
They found that metabolic reactions can cause a drop in SO2 levels, but only by producing other molecules in very large amounts that are not seen. The results set a hard limit on the amount of life that could exist on Venus without breaking our understanding of how chemical reactions work in planetary atmospheres.
“If life were responsible for the levels of SO2 we see on Venus, it would also break everything we know about Venus’ atmospheric chemistry,” Jordan said. “We wanted life to be a potential explanation, but when we run the models, it’s not a viable solution. But if life isn’t responsible for what we see on Venus, it’s still a problem to solve: there’s a lot of weird chemistry to follow. “.
Although there is no evidence of life eating sulfur hidden in the clouds of Venus, researchers say its method for analyzing atmospheric signatures will be valuable when JWST, the successor to the Hubble Telescope, begins returning images of other planetary systems later this year. Some of the sulfur molecules in the current study are easy to see with JWST, so learning more about the chemical behavior of our next-door neighbor could help scientists figure out similar planets across the galaxy.
“To understand why some planets are alive, we need to understand why other planets are dead,” Shorttle said. “If life somehow managed to sneak into Venusian clouds, it would completely change the way we look for chemical signs of life on other planets.”
“Even if ‘our’ Venus’ is dead, it’s possible that Venus-like planets from other systems could harbor life,” said Rimmer, who is also affiliated with Cambridge’s Cavendish Laboratory. “We can take what we’ve learned here and apply it to exoplanetary systems; that’s just the beginning.”
The research was funded by the Simons Foundation and the Science and Technology Facilities Council (STFC), part of the UK Research and Innovation (UKRI).