The proportion of water in the clouds of Venus is less than sufficient to support life

It was long believed that the intense pressures and heat on Venus made life on its surface virtually impossible. But last September, when scientists announced the possible discovery of Phosphine gas in the atmosphere of Venus -This is one of the biological effects of life- Some have questioned the possibility of microbial life in the clouds of the planet.

However, it may be better for them to temper their expectations; A new study has indicated –Posted in Nature astronomy– that there is simply not enough water on Venus to support the existence of life as we know it in the clouds.

“It is well known that life needs water, of course,” says John Holsworth, a microbiologist at Collins University in Belfast and lead author of the new study. The new findings show that the water concentrations in the clouds of Venus are “as low as 1%” of the amount of water needed by even the hardiest microorganisms to survive on Earth. “These concentrations are almost at the end of the spectrum – which is far too important to ignore – of what is required for working life,” he adds.

In 1978, NASA launched the Pioneer mission to Venus, which consisted of an orbiter and a group of four small probes launched into the atmosphere of Venus. The atmosphere contains traces of deuterium, a heavy isotope of hydrogen, which can cause water to break down. Scientists have wondered if Venus once held more water and if large amounts of it were left in the atmosphere.

In 2020 we will find that there is a possibility The presence of phosphine gas in the atmosphere of Venus. possesses Scholars put the script It is possible that the water cycle in the sulfur-rich clouds of Venus allows microbes to be contained in tiny water droplets at high altitudes, where new spores can be hydrated to maintain the life cycle. Although the surface of the planet is hell, its clouds are stable and softer.

However, new research makes this scenario unlikely. The study focuses on “water activity”, that is, the amount of water that a microorganism can use, measured in terms of a value ranging from zero to one. For this study, the research team sought to measure the activity of water in clouds by calculating the relative humidity of the atmosphere (i.e. the amount of water that saturates air at a certain temperature). In this study, the scientists relied on Aspergillus penicilloides, a fungus capable of living in conditions of extreme drought, as a baseline for the water scarcity that organisms can tolerate while continuing their metabolic and reproductive functions. The answer is a water activity number of 0.585, which is practically the “life limit” for biological activity as we know it.

Using atmospheric data collected from previous Venus missions and new models for assessing water activity, Holzworth and his team calculated water activity in Venus clouds. at an altitude of 68 to 42 km; The temperature that allows life to exist varies between minus 40 degrees Celsius and 130 degrees Celsius. They found that the water activity is at best 0.004. “There’s not the slightest chance that life on Venus is the most drought tolerant microbe on Earth,” Holsworth said.

The researchers also point out that Venus’ atmosphere is saturated with harmful elements that likely prevent cellular systems from functioning properly (such as sulfuric acid which dries up cells), even assuming the same activity of water is increased. at a higher value.

Some other planets, however, did better. The team also calculated the water activity in the clouds of Venus, which is equal to 0.537 (a value close to the value of the Earth’s atmosphere, and slightly lower than the “life limit” of Earth), while in Jupiter’s clouds, this value reached 0.585 in places where the temperature varies between 10 degrees Celsius and minus 40 degrees Celsius. “We cannot be sure that Jupiter’s clouds are habitable,” said Christopher MacKay, a NASA scientist and co-author of the study. But we can confirm that it is not limited to aquatic activity.

These results need to be confirmed by further studies, but the authors are very confident in their validity, even with Two new NASA missions And an ESA mission to Venus towards the end of this decade.

But, of course, there are some things to be aware of. “Our discussions of life on other worlds should be based on what we know about life on Earth, because we have the basis of it,” Mackay says. But I really hope that when we find life elsewhere, it will be very different, ”a biochemical system that works well beyond what we have seen here on Earth.

While life on Venus seems unlikely in light of these new findings, it doesn’t necessarily mean that Venus has always been desolate. There is a complete history hidden for this planet, and scientists seek to study it.