Venus’ clouds have captivated Earth’s inhabitants for decades. They form dazzling mirrors that cover the planet’s surface, and in the 1950s an Israeli scientist speculated that clouds might hide a world full of insect life that could withstand intense heat.
When the Russian spacecraft Venera took pictures of the surface in 1975, no insects were found. Venus is a lonely hell, a victim of the runaway greenhouse effect that has raised temperatures on Earth to more than 850 degrees Fahrenheit—hot enough to melt lead. But in the clouds, a lighter atmosphere awaits any potential alien life form.
In the air, life may find a way.
At least, that is one hypothesis. It could happen on Earth… so why not somewhere else? Last year, the idea that microbes He might call Venus’ atmosphere home That’s backed up by a study that claims to have detected elevated levels of phosphine – an unstable gas linked to biological activity – in the cloud surfaces of our sister planet. This gave rise to the theory that microbes in clouds can produce gas.
However, when scientists decode the phosphine signal, the chances it may be a sign of life in Venus’ clouds seem to be getting smaller.
On Monday, the prospect of microbial communities drifting into the clouds took another hit.
of A study published in the journal Nature AstronomyThe researchers ruled out the possibility of life – as we know it – in the Venusian clouds. Clouds are uninhabitable.
“The most extreme life on Earth has absolutely no chance of living in the Venusian clouds,” said John Hallsworth, a microbiologist at Queen’s University Belfast and lead author of the new research paper.
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Venus is hot right now, and three missions to the planet are expected by the end of 2020.
NASA/JPL-Caltech
The problem is the availability of water. When planetary scientists look for life elsewhere in the universe, they look for water because it is so essential to life. Venus’ clouds may seem like a good place to start, but they’re not the kind of clouds we’re used to seeing on Earth. Venus’ clouds are made up mostly of liquid droplets of sulfuric acid — the substance we use to clean waterways — at concentrations that Hallsworth describes as “biologically hostile.”
These details already put microbial life in the background, but Halsworth and his team wanted cold, hard data to assess the possibilities. They studied data collected by spacecraft diving into Venus’ atmosphere to analyze water activity in the clouds and also turned their attention to Mars and Jupiter.
phosphine dream
In September 2020, astronomers announced Detection of excessive amount of phosphine gas in the upper atmosphere of Venus. The research team was baffled by this unexplained chemistry due to phosphine on Earth – The smell of rotten fish Can be produced by microbes.
The researchers were quick to point out that their findings were not Last Signs of life are in the clouds of Venus, but scientists and the public are talking about it all. This inspired Jim Bridenstine, then NASA administrator, to announce that it was time to prioritize Venus. Venus fever spreads through planetary science. Suddenly, The idea of looking for life on Mars It feels like a distant memory.
The possibilities of life on Venus are puzzling, but scientists are starting to double check their discoveries. After phosphine was announced, another research group began looking at data obtained from the ALMA Ground Telescope. Secondary examination appears to indicate that the phosphine signal may or may not be as strong as originally thought.
This is where Hallsworth and his colleagues set off. For nearly three decades, Hallsworth has been investigating how water activity affects microbial life. His work explores the lower limits of life – or how “dry” life was before biological activity collapsed.
Knowing that Venus’ clouds are high in sulfuric acid, which reduces water activity, he said the “alarm bell rings” before even reading the phosphine paper. His colleagues turned to him to ask if he knew any water activity in the clouds, hoping to paint a clearer picture of what was going on there.
But he didn’t see, so the team got to work. In two weeks, Hallsworth and his group analyzed data collected by NASA’s Pioneer probe and Russia’s Venera, a swarm of spacecraft that crashed into Venus’ atmosphere in the 1970s. The data collected by the planes gave them insight into the temperature, pressure and water trapped in the clouds.
desert sky
Any potential microbe floating in the Venusian clouds would be in a very hostile environment. About 30 to 44 miles above the surface, in the clouds, it is drier than the most extensive subtropical desert on Earth: the Sahara.
“Venus clouds are drier than the Sahara,” said Hallsworth, noting that the Sahara has about 0.25 water activity, while Venus’ clouds only have 0.004 water activity. This number for Venus is too extreme to support any life that we know of.
“The most drought-tolerant microbes on Earth will stand no chance on Venus,” Hallsworth said.
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Venus is drier than the Sahara, the third driest desert on Earth.
Florian Kaiser/Getty Images
Not only is its water activity very low, but had the microbes discovered a drop of liquid in Venus’ clouds — an oasis in a desert sky — their fate would not have been better. This oasis of potential is actually a poisonous droplet of sulfuric acid. Any microorganism will find too much acidity.
“No known microbial cell can remain intact at high concentrations of sulfuric acid in Venusian cloud droplets,” Halsworth said.
Microbes that found themselves in such a place would face instant death, tearing their membranes and spilling their guts.
Hallsworth’s previous work investigated the outer limits of microbial life on Earth. In terms of water activity, a fungus known as Aspergillus penicillioides, which is found in old books or tied up in the dust inside pillows and blankets, reigns on our planet. In 2017, Hallsworth Laboratories published a paper It was found that the fungus can grow and divide at a water activity of 0.585. This is impressive for Earth’s organisms.
They used this figure – 0.585 water activity – as the microbial tolerable limit, but water activity in Venus’ clouds was twice as small by volume.
Mars also lacks water activity to facilitate life in its atmosphere – it is very cold – but other planets in our solar system have water activity exceeding 0.585. These are surprising candidates for extraterrestrial homes.
Ruler of Jupiter
The gas giant Jupiter towers over all the planets orbiting the sun. It’s wild, and like Venus, it’s famous for its charms. When the research team analyzed water activity in Jupiter’s atmosphere, they found that it was at a level high enough to allow microbes to inhabit.
“We didn’t expect that at all,” Hallsworth said.
Using readings from NASA’s Galileo probe, which launched in 1989 and launched the probe into the gas giant’s atmosphere in 1995, the team revealed that somewhere beneath Jupiter’s crooked surface, life exists.
“There is at least a layer in Jupiter’s clouds where water needs are met,” Chris McKay, a planetary scientist at NASA’s Ames Research Center and co-author of the paper, told a news conference.
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Water activity in Jupiter’s clouds is allowed for life.
NASA/JPL-Caltech/SwRI/MSSS/Image Processing by Kevin M. Gill
However, the team was quick to point out that this is not an indication of life on this giant planet. The activity of the water just shows that the microbes we know on Earth could inhabit different layers of Jupiter’s atmosphere. Halsworth said whether Jupiter is currently inhabited would require “a new study”, but there are some fundamental questions that need to be answered first.
“We have to demonstrate a bioavailable source of energy and all the essential nutrients for life,” he said.
The find also extends further into the solar system. Whether water activity on Saturn, Neptune or Uranus is high enough for life to develop is an open question – there is no investigative data for the team to assess. However, Halsworth noted that “none of them would be expected to have a high layer of water activity” and they would be much colder than Jupiter, making it difficult for life to survive there.
And what next? outside the solar system? Studying water activity in the atmospheres of exoplanets using NASA’s James Webb Space Telescope, due for launch in October, could provide another way for planetary scientists to assess habitability in the distant universe.
So you’re saying they’re not aliens?
In a research paper published in Astrobiology last year lastThe research team that discovered the phosphine signal on Venus suggested how life could survive in a droplet of liquid 30 miles above the surface.
They hypothesized that the microbes might reside in the liquid droplets for a short time, before drying out and floating to the planet’s surface. Eventually, they can be lifted back into the upper layers of Venus’ atmosphere and are able to re-moisten and continue their life cycle.
The newspaper published on Monday dealt a crushing blow to this hypothesis.
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Illustration of the Galileo spacecraft, transmitting atmospheric data captured in Jupiter’s clouds to Earth.
NASA/JPL
If there’s life on Venus, it’s unlike anything we’ve seen on Earth—and it can survive without water, the life-giving stuff involved in many aspects of terrestrial biology.
This leaves us with a lingering question: Where does phosphine come from?
Cannot be reanalyzed Phosphine detection at very high levels sangat. Then suggest another team The signal is not phosphine at all, but sulfur dioxide. Another team suggested it might be there, but at a much lower level than previously estimated. At lower levels, phosphine can be explained by volcanic eruptions – and Venus has an active volcano.
If the sign was legit, Venus would be even more mysterious.
Laura McKimish, a planetary scientist at Australia’s University of New South Wales who was also not affiliated with the study, said.
Whatever the phosphine signal, Venus is now a premium travel destination and a fleet of interplanetary probes will be visited over the next decade.
NASA plans to send two spacecraft by the end of 2020, including one known as Davinci+, which will specifically investigate the atmosphere. The European Space Agency has plans of its own to visit Venus, too, with the mission known as EnVision. Both are expected to provide a more comprehensive view of Venus’ atmosphere and obtain more data about its composition, but they are not expected to change the idea of the presence of Earth-like microbes in clouds.
“It’s hard to imagine that the results will change as we do more exploration,” McKay said.
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