Life on Venus? Astronomers see a signal in their clouds

Science News

Astronomers on Earth have detected signs of what could be life in the toxic atmosphere of the planet Venus.

If the finding is confirmed by subsequent telescope observations and future space missions, it could direct scientists\’ attention to one of the brightest objects in the night sky. Venus, named after the Roman goddess of beauty, bakes at temperatures of hundreds of degrees and is shrouded in clouds that contain droplets of corrosive sulfuric acid. Few looked to the rocky planet as a possible home for life.

Instead, scientists have been looking for signs of life elsewhere for decades, most notably by looking at Mars and, more recently, Europa, Enceladus and other icy moons of the major planets.

An image provided by NASA shows an artist\’s conception of the surface of Venus. Hot enough to melt metal and with clouds filled with acid, any life that could survive in Venus\’ atmosphere would have to be able to withstand extremes. Rick Guidice/NASA via The New York Times
The astronomers, who published their findings in two publications, did not gather or photograph any Venusian microbes. They did, however, find a chemical – phosphine – in the dense atmosphere of Venus using powerful telescopes. After much investigation, experts conclude that the only explanation for the chemical\’s origin is something that is currently alive.

Some scholars reject this explanation, claiming that the gas could be the consequence of unexplained atmospheric or geological processes on a planet that remains a mystery. However, the discovery will encourage some planetary scientists to wonder whether humanity has overlooked a planet that was previously more Earth-like than any other world in our solar system.

“This is a surprising and \’out of the blue\’ discovery,” said Sara Seager, a planetary scientist at the Massachusetts Institute of Technology and one of the authors of the publications (one published in Nature Astronomy and another submitted to the journal Astrobiology). “It will definitely fuel more research into the possibilities of life in Venus\’ atmosphere.”

“We know this is an extraordinary discovery,” said Clara Sousa-Silva, a molecular astrophysicist at Harvard University and another of the authors whose research focused on phosphine. “We may not know how extraordinary without returning to Venus.”

“There has been a lot of buzz about phosphine as a biosignature gas for exoplanets recently,” said Sarah Stewart Johnson, planetary scientist and director of the Johnson Biosignatures Lab at Georgetown University, who was not involved in the research. “How nice to meet you on Venus.”

She added: “Venus has been ignored by NASA for so long. It\’s really a shame.”

“This is very exciting!” said David Grinspoon of the Planetary Science Institute in Tucson, Arizona, who was not involved in the research but has long championed the potential for life in the clouds of Venus.

“but this may be the first observation we\’ve made that reveals an a̳l̳i̳e̳n̳ biosphere and, what do you know, it\’s on the closest planet to home in the entire cosmos.” he said.

NASA Administrator Jim Bridenstine responded to the discovery on Twitter, writing, “It\’s time to prioritize Venus.”

Venus is one of the most beautiful celestial objects in the sky. However, the closer you look, the less attractive it becomes.

Venus, also known as Earth\’s twin, has approximately the same mass as Earth. Many scientists believe that Venus was previously covered in water and had an environment in which life as we know it could have thrived.

Earth was not always so welcoming to humans in the early days of the solar system. There was life here at that time, even an entire biosphere that did not survive in the subsequent oxygen-rich atmosphere. And just as Earth evolved into a habitat for jellyfish, ferns, dinosaurs and Homo sapiens, Venus was turned into hell by something.

Today, the atmosphere of the second planet from the sun is suffocated by carbon dioxide gas, and surface temperatures average over 800 degrees Fahrenheit. Venus\’ dense atmosphere produces a pressure of over 1,300 pounds per square inch on anything near the surface. That\’s more than 90 times the 14.7 pounds per square inch at sea level on Earth, or the equivalent of 3,000 feet underwater in the ocean.

It\’s not an easy place to visit or research, but that doesn\’t mean people haven\’t tried it. Several robotic missions to Venus have been attempted by space projects, many of which were part of the Soviet Union\’s Venera series. However, the planet eats metal, melting and crushing spaceships that landed there within minutes. Only two attempts were able to directly capture photographs of the planet\’s surface.

Unlike Mars, which is currently surrounded by orbiters and hovered by NASA rovers, Venus is being examined by only one probe, the only Japanese spacecraft Akatsuki. Future missions to the planet are still ideas.

Despite the fact that the surface of Venus is like a blast furnace, a layer of clouds just 31 miles below the top of its atmosphere can reach temperatures as low as 86 degrees Fahrenheit and have pressures comparable to those at ground level. from the earth. Many planetary scientists, such as Carl Sagan and Harold Morowitz, who came up with the idea 53 years ago, believe that life could exist there.

Jane Greaves, an astronomer at Cardiff University in Wales, set out in June 2017 to verify this notion by looking for indications of various molecules on Venus with the James Clerk Maxwell Telescope in Hawaii. Different species of molecules absorb radio waves with different characteristic wavelengths that pass through clouds. Phosphine was one of the compounds. One of the chemicals was phosphine. She didn\’t expect to find him.

“I was intrigued by the idea of ​​looking for phosphine, because phosphorus can be a kind of deterrent to life,” Greaves explained.

Chemists actually liken phosphine to a pyramid, with a phosphorus atom on top of three hydrogen atoms. Cassini, a NASA mission, discovered in the atmospheres of Jupiter and Saturn. Sousa-Silva says that in that environment, life is not necessary to create phosphine. Massive heat and pressure can compress the phosphorus and hydrogen atoms, forming the molecule.

However, the researchers claim that there is not enough energy on smaller, rocky worlds like Earth and Venus to produce large amounts of phosphine in the same way. However, one type of life seems to be particularly good at making it: anaerobic life, or microbial organisms that do not require or use oxygen.

According to Sousa-Silva, “as far as we know, only life can produce phosphine” in these worlds. She has long stud̳i̳e̳d the gas, with the theory that finding it being emitted by rocky planets orbiting distant stars could be proof that life exists elsewhere in the Milky Way.

Phosphine can be found in our intestines, in the feces of badgers and penguins, some deep-sea worms, and other biological conditions associated with anaerobic species. It is also highly poisonous. It was used in chemical warfare by the military and is also used as a fumigant on farms. Walter White, the main character of the TV show “Breaking Bad”, decides to kill two rivals.

However, scientists have struggled to explain how Earth\’s bacteria survive.

“There\’s not a lot of understanding of where it comes from, how it forms, stuff like that,” said Matthew Pasek, a geoscientist at the University of South Florida in Tampa. “We\’ve seen this associated with where the microbes are, but we haven\’t seen a microbe do that, which is a subtle but important difference.”

Greaves informed Sousa-Silva that she had identified the phosphine, which S̳h̳o̳c̳k̳ed her.

“That moment really messes with my mind because it took me a few minutes to consider what was going on,” she said.

If there was phosphine on Venus, she concluded there could be only one explanation: anaerobic life.

“What we find circumstantially also makes perfect sense with what we know thermodynamically,” she said.

The team needed a more powerful telescope, so in March 2019, scientists deployed the Atacama Large Millimeter Array in Chile.

This time, they found that all the evidence led to phosphine, and that there was a lot, ranging from 5 to 20 parts per billion. While these numbers may seem tiny, they are thousands of times greater than those found in Earth\’s atmosphere.

An image of Venus, made with data recorded by the Japanese spacecraft Akatsuki in 2016. So close, so similar and very mysterious, the planet surprises scientists with a chemical signature seen in its clouds. Project PLANET-C/JAXA Team via The New York Times

The researchers spent a year simulating the Venusian environment in computer simulations to explore various hypotheses about the origins and abundance of phosphine.

“Light is constantly breaking down phosphine, so you have to continually replenish it,” said William Bains, a biochemist at MIT and one of the papers\’ co-authors.

According to the researchers\’ models, volcanic activity and lightning on Venus would not be enough to replenish this ever-disappearing phosphine. However, living things can produce enough gas.

“What we\’ve done is we\’ve ruled out all other sources of phosphine besides life,” Bains said.

Other planetary scientists disagree, claiming that a non-biological origin cannot be ruled out.

“Despite previous speculations (mostly from the same authors), this can hardly be considered a biosignature,” Gerald Joyce, a biologist at the Salk Institute in California who has experimented with creating life in a laboratory, said in an email. In their own paper, he noted, the researchers wrote that “phosphine detection is not robust evidence for life, only for anomalous and unexplained chemistry.”

James Kasting, a geoscientist and planetary habitability expert at Pennsylvania State University, expressed a similar concern, saying, “The atmospheric composition model they show is, at best, incomplete.”

The discovery also follows a history of detections of gases on other worlds that could be by-products of life. However, similar gases such as methane or oxygen burping on Mars can be created by chemical reactions that do not require life. So far, these signs have been puzzling, but they don\’t provide conclusive evidence of a̳l̳i̳e̳n̳s.

While few would question that this phosphine exists, what kind of life in the clouds of Venus would it take to produce the gas?

To exist in a highly acidic environment, these living things would have to evolve, possibly with protective outer layers comparable to microscopic life in Earth\’s most hostile environments.

Seager and his colleagues proposed in a publication that bacteria carried by air currents known as gravity waves can live, metabolize and multiply within droplets of sulfuric acid and water. And given the amount of gas produced, there would be a lot of these bacteria.

The best estimate of how these bacteria got there, she added, is that they started on the surface when Venus still had oceans 700 million years ago, but were taken to the skies when the planet dried up.

No one knows whether bacteria, if they exist, are based on DNA like we are or on something else entirely.

“When looking for life elsewhere, it\’s very difficult not to be Earth-centered,” Sousa-Silva said. “Because we only have this data point.”

Before their imaginations run wild, scientists want to collect additional data from the telescope and have their theories verified and challenged. The search could be aided by robotic space expeditions to Venus.

India\’s space agency, as well as a private rocket company, Rocket Lab, have proposed missions over the next few years.

And, after refusing to fund multiple Venus missions in previous decades, NASA has said it will evaluate a pair of planned spacecraft among four finalists vying for a funding round.

“Over the past two decades, we\’ve continued to make new discoveries that collectively imply a significant increase in the likelihood of finding life elsewhere,” said Thomas Zurbuchen, head of NASA\’s science directorate, which helps choose missions to study the solar system. “Many scientists would not have guessed that Venus would be a significant part of this discussion. But like a growing number of planetary bod̳i̳e̳s, Venus is proving to be an exciting place of discovery.”

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