Phosphine on Venus: Possible sign of life provokes heated debate


In the dense clouds that envelop Venus, there is perhaps something deadly floating around: a foul-smelling, combustible gas called phosphine, which is highly toxic to organisms that need oxygen to survive. Ironically, the scientists who announced yesterday that they found this noxious gas in the atmosphere of Venus think it could be a promising (albeit controversial) indication of the presence of life on our neighboring planet.

As far as we know, phosphine on rocky planets like Earth and Venus can only be produced by life – either by humans or by microbes. The chemical was used as a poison gas in World War I and is still produced as an agricultural pesticide. In addition, it is used in semiconductor manufacturing and is a harmful by-product of illegal methamphetamine manufacturing. But phosphine is also produced naturally by anaerobic bacteria, organisms that live in the oxygen-poor environment of rubbish dumps, swamps and even the intestines of animals.

Earlier this year, researchers concluded that the discovery of this chemical compound on another rocky planet could indicate the presence of alien metabolisms. They therefore proposed aiming the future’s strongest telescopes at exoplanets to search their atmosphere for signs of this harmful gas.

But now according to an article in the magazine Nature Astronomy that traces of phosphine have been found on a planet next door. “Of course I went completely crazy. I assumed it was a mistake, but I really wanted it not to be a mistake, ”says Clara Sousa-Silva, a postdoctoral fellow at the Massachusetts Institute of Technology (MIT) and also the one who previously had phosphine as a potential ‘biosignature’ marked.

Simply put, phosphine should not be present at all in the atmosphere of Venus. It is very difficult to produce and the chemical composition of the Venusian clouds would have to cause the molecule to break down before it can accumulate at a concentration that has now been measured. But it is too early to say that life exists outside our blue planet. Scientists point out that the measurement itself has yet to be verified, as the ‘signature’ of the phosphine described in the new study could also be an error signal from the telescopes or software used.

“It’s very exciting, but we are committed to this Pavlovian response by asking whether the results are accurate,” said David Grinspoon of the Planetary Science Institute. “If someone comes up with an extraordinary sighting that hasn’t been done before, then you have to wonder if they might have made a mistake.”

But if phosphine does indeed float in the dense cloud cover of Venus, its presence hints at two fascinating possibilities: that alien life forms have managed to connect phosphorus and hydrogen atoms, or that phosphine chemically works in a completely different and completely unexpected way. can come about, so without the presence of life.

Living in a ‘blackened hell’

Venus, the second rock from the sun, has long been considered Earth’s twin sister. The planet is about the same size as our home planet and has a similar gravity and composition. For centuries, people hoped that the surface of Venus was covered with oceans, lush vegetation, and fertile ecosystems – like a second oasis of life in the solar system. But gradually the dire reality became clear.

The first scientific observations of our neighboring planet showed that it is a hell where earthlings can die in various and terrible ways. On the surface of Venus, the temperature can reach a scorching 480 degrees Celsius. Under the dense blanket of clouds and mist that can sometimes reach a thickness of a hundred kilometers, the charred rocks are also exposed to an all-crushing atmospheric pressure more than 90 times higher than on Earth. In addition, Venus’ atmosphere, which is predominantly made up of suffocating carbon dioxide, also contains clouds of sulfuric acid.

Despite this, scientists have been considering the possibility of life in the higher Venusian cloud cover, where conditions are more friendly, for nearly 60 years. “While conditions on the surface of Venus make life there unlikely, the clouds of Venus are a very different story,” wrote Carl Sagan and Harold Morowitz in the magazine 1967. Nature.

Despite the presence of acids, these clouds contain the basic ingredients for life as we know it: sunlight, water and organic molecules. And halfway through the cloud cover, the temperature and air pressure are quite earthy. “It’s nice summer weather there, with lots of goodies to eat,” said Martha Gilmore, planetologist at Wesleyan University and head of a possible mission to Venus. The ‘treats’ she’s talking about are the molecules in the air that can be metabolized by microbes.

Early observations of Venus from Earth showed that parts of the Venusian atmosphere absorbed more ultraviolet light than expected, an anomaly that scientists believe could indicate the presence of floating microbes. Although the phenomenon can probably be attributed to the presence of sulfur-containing compounds, a handful of scientists have since looked into the possibility of floating organisms in the Venusian atmosphere; they looked at a scenario in which microbes possibly metabolized sulfur-containing compounds, could remain floating in the air in the ever-present cloud cover, and could even develop life cycles with latent periods at different heights.

“When I first started talking about this, there was a lot of resistance, especially because it’s such an extremely acidic environment,” says Grinspoon, who has been researching the possibility of living in the clouds since the mid-1990s. from Venus. But everything we have learned about life on earth shows that life forms will develop wherever they can. On our planet we find living microbes in extremely corrosive environments, such as hot springs and volcanic chimneys. We know that microbes regularly hitch a ride on cloud particles, and scientists have found floating organisms ten kilometers above the Caribbean Sea.


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