Life on Venus? Astronomers see a signal in Its clouds - Beyond The World
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Life on Venus? Astronomers see a signal in Its clouds

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

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

Instead, scientists have been looking for signs of life elsewhere for decades, mainly looking outward to Mars and, more lately, Europa, Enceladus, and other icy moons of the major planets.

Life on Venus? Astronomers see a signal in Its clouds 1
An image provided by NASA shows an artist’s conception of the surface of Venus. Hot enough to melt metal and with clouds full of acid, any life that could survive in the atmosphere of Venus would have to be capable of enduring extremes. Rick Guidice/NASA via The New York Times

The astronomers, who published their findings in a pair of publications, have not gathered or photographed any Venusian microbes. They have, however, found a chemical — phosphine — in the dense Venus atmosphere using powerful telescopes. After much investigation, the experts conclude that the only explanation for the chemical’s source is something that is currently alive.

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

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

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

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

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

“That is pretty damn exciting!” said David Grinspoon of the Planetary Science Institute in Tucson, Arizona, who was not involved in the research but has long advocated for the potential of life in Venus’ clouds.

 “but this could be the first observation we’ve made which reveals an alien 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 gorgeous celestial objects in the sky. However, the closer you look, the less appealing it gets.

Venus, also known as Earth’s twin, has about the same mass as Earth. Many scientists believe 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 back then, 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 changed into a hell by something.

Today, the atmosphere of the second planet from the sun is suffocated by carbon dioxide gas, and surface temperatures average more than 800 degrees Fahrenheit. Venus’ dense atmosphere produces a pressure of more than 1,300 pounds per square inch on anything near the surface. That is more than 90 times the 14.7 pounds per square inch at sea level on Earth, or the equivalent to being 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. 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 spacecraft that have landed there within minutes. Only two of them attempts succeeded in directly capturing photographs of the planet’s surface.

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

Despite the fact that Venus’s surface is like a blast furnace, a cloud layer just 31 miles below the top of its atmosphere may reach temperatures as low as 86 degrees Fahrenheit and has pressures comparable to that of Earth’s ground level. Many planetary scientists, like Carl Sagan and Harold Morowitz, who presented the idea 53 years ago, believe life could exist there.

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

“I got intrigued by the idea of looking for phosphine, because phosphorus might be a bit of a sort of go-no-go for life,” Greaves explained.

Chemists actually compare phosphine to a pyramid, with one phosphorus atom on top of three hydrogen atoms. Cassini, a NASA mission, discovered it in the atmospheres of Jupiter and Saturn. Sousa-Silva claims that in that environment, life is not required to create phosphine. Massive heat and pressure can jam the phosphorous and hydrogen atoms together, forming the molecule.

However, the researchers claim that there isn’t enough energy on smaller, rocky worlds like Earth and Venus to make huge amounts of phosphine in the same way. However, one type of life appears 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 can tell, only life can make phosphine,” on such worlds. She has long studied the gas, on the theory that finding it being emitted from rocky planets that orbit distant stars could be proof that life exists elsewhere in the Milky Way.

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

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

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

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

“That moment plays in my mind a lot, because I took a few minutes to consider what was happening,” she said.

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

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

The team required a more powerful telescope, therefore in March 2019, the scientists employed the Atacama Large Millimeter Array in Chile.

This time, they discovered that all evidence led to phosphine, and that there was a lot of it, ranging from 5 to 20 parts per billion. Although those figures may appear tiny, they are thousands of times greater than what is found in the Earth’s atmosphere.

Life on Venus? Astronomers see a signal in Its clouds 2
An image of Venus, made with data recorded by Japan’s Akatsuki spacecraft in 2016. So close, so similar and very mysterious, the planet is surprising scientists with a chemical signature spotted in its clouds. PLANET-C Project Team/JAXA via The New York Times

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

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

According to the researchers’ models, volcanic activity and lightning on Venus would not be enough to replenish this constantly vanishing phosphine. However, live beings may produce enough of the gas.

“What we’ve done is rule out all other sources of phosphine other than life,” Bains said.

Other planetary scientists disagree, claiming that a nonbiological origin cannot be ruled out.

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

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

The finding also follows a history of detections of gases on other worlds that can be byproducts of life. However, similar gases, such as methane or oxygen burps on Mars, can be created by chemical reactions that do not require life at all. So far, such signals have been intriguing, but they do not provide conclusive evidence of aliens.

While few question that this phosphine exists, what kind of life in Venus’s clouds would be required to produce the gas?

To exist in a high-acid environment, such living beings would have had to evolve, possibly with protective outer layers comparable to microscopic life in Earth’s most harsh settings.

Seager and her colleagues proposed in an publication that bacteria carried aloft on air currents known as gravity waves may live, metabolize, and multiply inside droplets of sulfuric acid and water. And, given the amount of gas produced, there would be plenty of these bacteria.

The best estimate for how these bacteria got there, she added, is that they began on the surface when Venus still had oceans 700 million years ago, but were driven into the heavens when the planet dried up.

Nobody knows if the bacteria, if they exist, are based on DNA like ourselves or on something altogether different.

“When looking for life elsewhere, it’s so hard to not be Earth-centric,” Sousa-Silva said. “Because we only have that one data point.”

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

India’s space agency, as well as a private rocket business, Rocket Lab, have proposed missions in the coming years.

And, after declining to fund several Venus missions in previous decades, NASA stated that it will evaluate a pair of planned spacecraft among four finalists contending for a round of financing.

“For the last two decades, we keep making new discoveries that collectively imply a significant increase of the likelihood to find life elsewhere,” said Thomas Zurbuchen, head of NASA’s scientific 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, just like an increasing number of planetary bodies, Venus is proving to be an exciting place of discovery.”

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