The unusual behavior of sulfur in Venus’ atmosphere cannot be explained by an “airborne” form of extraterrestrial life, a new study has found.
Cambridge University researchers have used a combination of biochemistry and atmospheric chemistry to test the “life in the clouds” hypothesis, which astronomers have speculated about for decades, and found that life cannot explain the composition of the Venusian atmosphere.
Any form of life in sufficient abundance is expected to leave chemical footprints in a planet’s atmosphere as it consumes food and expels waste. However, Cambridge researchers found no evidence of these fingerprints on Venus.
Even though Venus is devoid of life, the researchers affirm their findings, reported in the journal Nature Communicationcould be useful for studying the atmospheres of similar planets throughout the galaxy, and the possible detection of life outside our solar system.
“We’ve spent the past two years trying to explain the strange sulfur chemistry we see in the clouds of Venus,” said co-author Dr. Paul Rimmer of the Department of Earth Sciences at Cambridge. “Life is pretty good at weird chemistry, so we investigated if there’s a way to make life a potential 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 looked at the sulfur-based ‘food’ available in the Venusian atmosphere – it’s not something you or I would want to eat, but it’s the main energy source available,” Sean Jordan said. of the Institute of Astronomy, Cambridge, the first of the journal. author. “If this food is consumed by life, we should see evidence of it in specific chemicals lost and gained in the atmosphere.”
The models examined 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” out of the atmosphere at higher altitudes.
“If life is present, it must affect atmospheric chemistry,” said co-author Dr Oliver Shorttle of the Department of Earth Sciences and Cambridge Institute of Astronomy. “Could life be the reason why SO2 the levels on Venus are so low?”
The models, developed by Jordan, include a list of metabolic reactions that life forms would perform in order to obtain their “food” and waste by-products. The researchers ran the model to see if the reduction in SO2 could be explained by these metabolic reactions.
They found that metabolic reactions can lead to a drop in SO2 levels, but only by producing other molecules in very large quantities that are not visible. The results set a hard limit on the amount of life that could exist on Venus without exploding our understanding of how chemical reactions work in planetary atmospheres.
“If life was responsible for SO2 levels we see on Venus, it would also shatter everything we know about Venus’ atmospheric chemistry,” Jordan said. “We wanted life to be a potential explanation, but when we ran the models, it’s not a viable solution. But if life isn’t responsible for what we see on Venus, that’s still a problem to be solved – there’s a lot of weird chemistry to follow.”
Although there is no evidence of sulfur-eating life hidden in the clouds of Venus, the researchers say their method of analyzing atmospheric signatures will be useful when JWST, the successor to the Hubble telescope, starts 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 knowing more about the chemical behavior of our next-door neighbor could help scientists discover 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 squeeze into the Venusian clouds, it would totally 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 in 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 – this is just the beginning.”
Could acid-neutralizing lifeforms create habitable pockets in Venus’ clouds?
Sean Jordan, Proposed Energy Metabolisms Cannot Explain Venus’ Atmospheric Chemistry, Nature Communication (2022). DOI: 10.1038/s41467-022-30804-8. www.nature.com/articles/s41467-022-30804-8
Provided by the University of Cambridge
Quote: No signs of life (yet) on Venus (June 14, 2022) retrieved June 15, 2022 from https://phys.org/news/2022-06-life-venus.html
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