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The discovery of noxious gas on Venus could be a sign of life

Deep in the acidic clouds of Venus, astronomers have discovered a tempting gas never before found on the planet – a gas that, remarkably, could be a sign of life in the hellish world. The presence of the gas is not enough to be certain that Venus is home to life forms, but the fact that it exists in the planet’s clouds shows this something is going on there, which we don’t quite understand.

The gas in question is a nasty gas called phosphine, which is a toxic and explosive molecule with a lingering smell of garlic and dead fish. Astronomers discovered the putrid gas lurking in a layer of cloud on Venus, where temperatures are pretty close to those on our planet. They didn̵

7;t find much – just tiny traces in the swirling mixture of sulfuric acid clouds that surround the planet. “It’s the equivalent of a few tablespoons in an Olympic swimming pool,” says David Clements, an astrophysicist at Imperial College London and part of the team that made the discovery The edge.

But finding even a small amount of phosphine on Venus is tempting because the gas is made here on Earth. Either it is produced artificially by humans – into products such as fumigants or biological weapons – or it is a natural by-product of life. Phosphine is found in swamps and wetlands, where it is believed to be produced by microbes. It can also be found in the intestines of animals or in the poop they leave behind. Most importantly, it’s a gas that is almost exclusively associated with life on Earth, increasing the possibility that it could be a sign that microbes are floating in the Venusian clouds.

Or it could come from something we can’t understand yet. An international research team that is now in Natural astronomyI did my best to find other explanations for the gas they found on Venus. They modeled things like lightning strikes and meteors bombarding the planet’s surface to see if such phenomena could produce the amount of phosphine they saw. So far nothing fits together. “This is why this is such an extraordinary piece of evidence, because it must have come from something completely unexpected,” says Clara Sousa-Silva, molecular astrophysicist at MIT and one of the authors of the study The edge. “At some point you don’t have to explain it anymore. Unless we know of a strange way of making phosphine on terrestrial planets – and that’s life. “

The idea of ​​finding life on Venus may seem absurd as the planet embodies the definition of a hellish landscape. Venus is a barren wasteland surrounded by a thick atmosphere of carbon dioxide. Temperatures can rise to nearly 900 degrees Fahrenheit on the surface, hot enough to melt lead (and most spacecraft). Heavy clouds swirling around the planet are made up of sulfuric acid droplets so pissed off, we can’t even measure them on our own pH scale. “It is literally billions of times more acidic than the most acidic environment on earth,” says Janusz Petkowski, astrobiologist at MIT and author of the study The edge.

Still, astronomers have considered the possibility that life forms may survive in this ruthless place, especially in the cloud covers of the planet. Famed astronomer Carl Sagan and biologist Harold Morowitz proposed the idea in 1967, and astronomers have speculated about it ever since. Scientists fixed dark spots in the clouds of Venus, regions that absorb more ultraviolet light than other areas. A possible explanation for this error? Large swaths of light-flooded microorganisms that swell and shrink over time, similar to massive algal blooms. “The idea already existed, but nobody had seriously investigated it until we suggested a life cycle for the bacteria,” suggested Sanjay Limaye, a planetary scientist at the University of Wisconsin, an explanation for life on Venus and was not part of it related to this study The edge.

Finding hard evidence of life in a harsh world like Venus is a particular challenge. Some probes that were sent to Venus actually melted while submerged to the surface, and none have yet found evidence of life. On Earth, astronomers can remotely examine the planet’s atmosphere to see if something biological has knocked out molecules. Hunting for these gases – called biosignatures – is one of the best ways astronomers can determine if life is lurking on another planet.

Phosphine has proven to be a fascinating gas. Recently, Sousa-Silva and some of the researchers in this discovery suggested phosphine as a possible biosignature because it is related to some life on earth. That association is still somewhat mysterious. We still don’t know exactly which bacteria on earth produce phosphine, but some laboratory studies suggest that complex microbial communities produce the substance. It also takes a lot of energy to make phosphine, and life is a particularly energetic source. “We don’t know why life on earth can make it, but it makes sense that only life can do it,” says Sousa-Silva. “Because it just wouldn’t spontaneously be done in an environment like Earth.”

The James Clerk Maxwell Telescope in Hawaii, one of two telescopes used to perform phosphine detection on Venus.
Image: Will Montgomerie / EAO / JCMT

With a view to phosphine, an international team of researchers used two ground-based telescopes – the James Clerk Maxwell Telescope in Hawaii and the Atacama Large Millimeter Array in Chile – to search for possible signatures of phosphine in the Venusian atmosphere. Sure enough, they found the gas in the atmosphere at a concentration of five to 20 parts per billion. That’s a lot when you compare it to how much is found on Earth where the gas is concentrated in parts per trillion and parts per quadrillion. “That’s all very much evidence for this exotic explanation of something that it replenishes and makes in large quantities,” says Sousa-Silva.

The potential for this discovery is certainly extraordinary, but no one is crying “aliens” yet. The astronomy community has been on this journey before, where one discovery is celebrated as the one that falls apart a little later. Perhaps the most famous example was the alleged discovery of fossilized bacteria in a Martian meteorite in 1996, which sparked a speech by then-President Bill Clinton. Over time, the claim did not stand up to the test. “I may not be jumping up and down here,” said Victoria Meadows, an astrobiologist at the University of Washington who was not involved in the study The edge. “We are in a situation where we have to wait and see. I think it’s a very fascinating discovery, but it definitely needs more research. “

First of all, we need to be sure that the gas is actually phosphine. The evidence isn’t particularly strong, and even the researchers admit the possibility that another gas, sulfur dioxide, could explain this signal. Further observations of the Venusian atmosphere are needed to truly confirm the presence of phosphine.

When the phosphine detection is confirmed, people go to work to find out where it came from. It may turn out that life isn’t even the best explanation. The phosphine may have been found in clouds with moderate temperatures, but the area is still a terrible place for life to survive, even for the toughest microorganisms. “There’s nothing in particular that says it’s biology,” says Rakesh Mogul, a biological chemist at California State Polytechnic University who focuses on extreme microbial life and is not involved in the study The edge. “There are still a lot of unknowns. And it’s nice to have biology as an answer, but as scientists we really need to support it and make sure we study all other possibilities thoroughly. “

An artist’s rendering of the Veritas spacecraft, a planned mission to Venus from NASA’s Jet Propulsion Laboratory.
Image: NASA / JPL-Caltech

When it turns out that life is As a good explanation, this discovery could seriously increase the clout of Venus as a place to visit in the future. Despite its proximity to Earth, Venus has remained largely unexplored over the past few decades, while our other neighbor Mars has received much more attention. The confirmation of phosphine on Venus could lead to the creation of new microbial hunting missions on the cloudy planet. The requirements for this type of mission will likely need to be much stricter than before to avoid contamination of the Venusian environment. “It has to be a global conversation about the ethics of future observations of Venus,” says Sarah Rugheimer, an astrobiologist at Jesus College, Oxford, who was not involved in the study The edge. “If you talk about exploring the Venusian atmosphere and possibly disrupting the habitat, that’s what we need to talk about.”

Finding strong evidence of life on Venus would completely change our understanding of what constitutes a habitable planet. In our quest for life outside of Earth, we have focused on planets that look very similar to ours. But Venus might tell us that we need to broaden our criteria. “When it comes to microbes, life is really different and can create creatures in environments we might never expect,” says Rugheimer.

Ultimately, it all comes down to one question: Are we alone? Microbes on Venus may not seem that impressive, but if life can form on two worlds right next to each other, it opens up the possibility that life in the universe is much more common than we think.

No matter what, this discovery is just the beginning of a long journey to learn more about Venus and its potential for habitability. At the moment there is no definitive answer. There can never be. “As they say, exceptional claims require exceptional evidence,” says Clements of the Imperial College of London. “We have pretty good evidence, I wouldn’t say it’s extraordinary anymore.”

To delve deeper into this discovery, The Verge made a video about the phosphine detection that you can read in the article above. Let us know what you think about the find in the comments.

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