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Venus became the ‘yeti’ of astrobiology a couple of years ago when a group of researchers made public the possible discovery in its atmosphere of phosphorus, a gas that is normally generated during the decomposition of organic matter. The announcement unleashed a media storm due to the possibility that aerial life existed on the neighboring planet, although it did not take long for numerous studies to come out that questioned the biological origin of the phosphine and even its existence.
It was not the first time that the possibility of Venusian life had been speculated on. A paper in 2004 proposed that sulfur in the atmosphere could be used by microbes as a means of converting ultraviolet light to other wavelengths that would even allow photosynthesis.
Since then, the unusual behavior of the sulfur in the atmosphere of Venus and the possibility of life in the clouds have been studied.
At an altitude between 40 and 60 km above the hot surface, the atmosphere of Venus resembles that of Earth: the air pressure is very similar and the temperatures range from zero to 50 degrees Celsius, acceptable for some beings. microbial.
However, new research from the University of Cambridge concludes that the unusual behavior of sulfur in the atmosphere of Venus cannot be explained by biological origin. That is, there are no microscopic beings swinging through the clouds.
“We’ve spent the last two years trying to explain the strange sulfur chemistry we see in the clouds of Venus,” he says. Paul Rimmer, from the Cambridge Department of Earth Sciences. “We have been studying whether there is a way to make life a possible explanation for what we see.”
And, as published in the magazine ‘Nature Communications’, the answer is no.
Any life form in sufficient abundance is expected to leave chemical footprints in a planet’s atmosphere as it consumes food and expels waste. However, the researchers found no evidence of these fingerprints on Venus.
The team used a combination of atmospheric and biochemical models to study the chemical reactions expected to occur, given the known sources of chemical energy in the atmosphere of Venus.
“We looked at the sulfur-based ‘food’ available in the atmosphere of Venus: it’s nothing you or I would want to eat, but it’s the main source of energy available,” says first author Sean Jordan of the Cambridge Institute for Astronomy. from the article. “If that food is being consumed by life, we should see evidence through the loss and gain of specific chemicals in the atmosphere,” he says.
Sulfur dioxide
The models looked at a particular feature of the atmosphere of Venus: the abundance of sulfur dioxide (SO 2 ). On Earth, most of the SO 2 in the atmosphere comes from volcanic emissions. On Venus, there are high levels of SO 2 lower down in the clouds, but it is somehow ‘sucked’ out of the atmosphere at higher altitudes. Could life be the reason SO 2 levels on Venus drop so low?
The models, developed by Jordan, include a list of metabolic reactions that life forms would carry out to obtain their ‘food’ and waste by-products. The researchers ran the model to see if the reduction in SO 2 levels could be explained by these metabolic reactions.
They found that metabolic reactions can result in a drop in SO 2 levels, but only by producing other molecules in very large amounts that are not seen. The results put a hard limit on the amount of life that could exist on Venus without destroying our understanding of how chemical reactions work in planetary atmospheres.
“If life were responsible for the SO 2 levels we see on Venus, it would also shatter everything we know about the atmospheric chemistry of Venus,” says Jordan. “We wanted life to be a possible 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, that’s still a problem to be solved: there’s a lot of weird chemistry to follow,” he says.
Similar planets
Although there is no evidence of sulfur-eating life hiding in the clouds of Venus, the researchers say their method of analyzing atmospheric signatures will be valuable when the James Webb , the successor to the Hubble Telescope, begins sending back images of other planetary systems in the late of this year. Some of the sulfur molecules in the current study are easy to see with the new observatory, so learning 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,” says Shortttle. “If life somehow managed to sneak into the clouds of Venus, 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 similar planets in other systems could support life,” suggests Rimmer. “We can take what we’ve learned here,” he adds, “and apply it to exoplanetary systems; This is just the beginning”.
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