Image showing the planet Venus

No signs of life have been detected on Venus

Scientists have spent the past two years explaining the strange sulfur chemistry seen in Venus’s clouds. They investigated if there was a way to make life a potential explanation for what is observed.

Using a combination of atmospheric and biochemical models, scientists from the University of Cambridge tested the “life in the clouds” hypothesis and discovered that life cannot explain the composition of the Venusian atmosphere.

Scientists have found that the study suggests that the unusual behavior of sulfur in Venus’ atmosphere cannot be explained by an “airborne” form of sulfur. extraterrestrial life.

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, scientists have found no evidence of these fingerprints on Venus.

Even though Venus is devoid of life, the study could be useful for studying the atmospheres of similar planets throughout the galaxy and the possible detection of life outside our solar system.

Co-author Dr Paul Rimmer from Cambridge’s Department of Earth Sciences said: “We’ve spent the past two years trying to explain the strange sulfur chemistry we see in the clouds of Venus. 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.

Sean Jordan of the Cambridge Institute of Astronomy, the paper’s first author, said: “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. If this food is eaten through life, we should see evidence of this through specific chemicals lost and gained in the atmosphere.

Scientists have mainly observed the abundance of sulfur dioxide (SO2) in the Venusian atmosphere. On Earth, most of the SO2 in the atmosphere comes from volcanic emissions. On Venus, there are large amounts of SO2 lower in the clouds, but it is somehow “sucked out of the atmosphere at higher altitudes”.

Co-author Dr Oliver Shorttle of the Department of Earth Sciences and the Institute of Astronomy, Cambridge, said: “If life is present, it must affect atmospheric chemistry. Could life be the reason SO2 levels on Venus are so low? »

In their study, the scientists used models that include a list of metabolic reactions life forms would perform to obtain their “food” and waste byproducts. Using the models, they determined whether these metabolic reactions could explain the reduction in SO2 levels.

They found that metabolic reactions can cause SO2 levels to drop, but only by producing other molecules in very large quantities that are not visible. The findings limit the amount of life that could exist on Venus without destroying our understanding of how chemical reactions work in planetary atmospheres.

Jordan said, “If life were responsible for the SO2 levels we see on Venus, it would also shatter everything we know about The atmospheric chemistry of Venus. We wanted life to be a potential explanation, but that wasn’t a viable solution when we ran the models. 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.”

Scientists have found no evidence of sulfur-eating life in the clouds of Venus. Still, they think the study will be useful when JWST, the successor to the Hubble Telescope, begins 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.

Shortly said, “To understand why some planets are alive, we need to understand why other planets are dead. If life somehow managed to squeeze into the Venusian clouds, it would change the way we look for chemical signs of life on other planets.

Rimer said, “Even if ‘our’ Venus is dead, it’s possible that Venus-like planets in other systems could harbor life. We can take what we’ve learned here and apply it to exoplanetary systems – it’s not only the beginning.

Journal reference:

  1. Jordan, S., Shorttle, O. & Rimmer, PB The proposed energy metabolisms cannot explain the atmospheric chemistry of Venus. Common Nat 13, 3274 (2022). DO I: 10.1038/s41467-022-30804-8

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