No signs (yet) of life on Venus

No signs (yet) of life on Venus

News – The unusual behavior of sulfur in Venus’ atmosphere can not be explained by an “air” form of extraterrestrial life, according to a new study.

Researchers at the University of Cambridge used a combination of biochemistry and atmospheric chemistry to test the “life in the clouds” hypothesis, which astronomers have been speculating about for decades, and found that life could not explain the composition of the Venusian atmosphere.

Each life form in sufficient abundance is expected to leave chemical fingerprints on a planet’s atmosphere as it consumes food and expels waste. However, Cambridge scientists found no evidence of these fingerprints on Venus.

Although Venus lacks life, scientists say resultsreported in the journal Nature communicationcan be useful for studying the atmosphere on similar planets throughout the galaxy, and the possible discovery of life outside our solar system.

“We’ve spent the last two years trying to explain the strange sulfur chemistry we see in the clouds of Venus,” said the co-author. Dr. Paul Rimmer from the Cambridge Department of Earth Sciences. “Life is pretty good at weird chemistry, so we’ve studied if there is 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 like to eat, but it’s the main source of energy available,” he said. Sean Jordan from Cambridge’s Institute of Astronomy, the paper’s first author. “If that food is consumed by life, we should see evidence of it by losing specific chemicals and accumulating in the atmosphere.”

The models looked at a special 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 somehow it is “sucked out” of the atmosphere at higher altitudes.

“If life is present, it must affect the chemistry of the atmosphere,” said the co-author Dr. Oliver Shorttle from the Cambridge Department of Earth Sciences and the Institute of Astronomy. “Can life be the reason for SO2 the levels on Venus are decreasing so much? “

The models, developed by Jordan, include a list of metabolic reactions that life forms would perform to get their “food” and waste by-products. The researchers ran the model to see if the reduction in SO2 the levels can be explained by these metabolic reactions.

They found that the metabolic reactions can result in a decrease in SO2 levels, but only by producing other molecules in very large quantities that are not visible. The results set a hard line for how much life could exist on Venus without blowing apart our understanding of how chemical reactions work in planetary atmospheres.

“If life was responsible for SO2 levels we see on Venus, it would also break everything we know about Venus’ atmospheric chemistry, ”said Jordan. “We wanted life to be a potential explanation, but when we drove the models it is not a sustainable solution. But if life is not responsible for what we see on Venus, it is still a problem to be solved – there is a lot of strange chemistry. To follow up.”

Although there is no evidence that sulfur-eating life is hidden in the clouds of Venus, scientists say that their method of analyzing atmospheric signatures will be valuable when JWST, the successor to the Hubble Telescope, will begin 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 neighbor can help scientists find 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 the Venusian clouds, it would totally change the way we search for chemical signs of life on other planets.”

“Even if ‘our’ Venus is dead, it is possible that Venus-like planets in other systems may be worth living,” says Rimmer, who is also affiliated with the Cambridge Cavendish Laboratory. “We can take what we have learned here and apply it to exoplanetary systems – this is 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).

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