Venus does not have enough water in its clouds to support life

In 1978, NASA launched the Pioneer Venus mission, consisting of an orbiter and a group of four small probes that were dropped into the Venusian atmosphere. There were signs of deuterium in the atmosphere – a heavy isotope of hydrogen that can result from the breakdown of water. Scientists wondered if Venus could have been home once for a larger amount of water, and if some had been attacked around in larger amounts in the atmosphere.

Fast forward to 2020 and possible detection of traces of phosphine in the atmosphere of Venus. The scientific ones contemplating a scenario as a potential water cycle in heavy clouds of Venus sulfuric acid could allow Venus microbes to exist in droplets at high altitudes and produce spores that could be hydrated and maintain a reproductive life cycle. Even if the surface of the planet is hell, its clouds are stable and more temperate.

Well, the new card means it’s pretty unlikely. The study focuses on “water activity,” or the amount of water that is available for microorganisms to be used, measured on a scale from 0 to 1. For this study, the research team sought to measure the activity of water in the clouds by calculating the relative humidity (the amount of water that has saturated the air at a given temperature). Scientists have used it Aspergillus penicillioides, a fungus capable of surviving in some of the driest conditions imaginable, such as a baseline for understanding the amount of water scarcity an organism can withstand while still being able to perform metabolic and reproductive functions. The answer is a water activity point of 0.585 – in fact the “life limit” of biological activity as we know it.

Using atmospheric data collected from past Venus missions and using more recent models to estimate water activity, Hallsworth and his team calculated the water activity of Venus clouds 68-42 miles long. altitude, where life-tolerant temperatures range from -40 ° C to 130 ° C. They found that water activity is, at best, 0.004. “Earth’s most drought-tolerant microbe wouldn’t have a chance on Venus,” Hallsworth says.

The researchers also reported that even though the water’s own activity was higher, Venus ’atmosphere was saturated with hostile elements that could prevent cellular systems from functioning properly (e.g., dehydrated sulfuric acid). and cells).

Other planets have gone better. The team also calculated water activity in Martian clouds to be 0.537 (comparable to Earth’s stratosphere, and only a smidge below the “life limit” for life on Earth), and in the Jupiter’s clouds happen to be at least 0.585 in places where the temperature is between -10 ° C and 40 ° C. “We can’t say that Jupiter’s clouds are habitable,” says Christopher McKay, a NASA scientist and co-author of in the study. “We can say that they are not limited by water activity.”

The findings should be confirmed with further study, but the authors are confident enough that they will not change, even with two new NASA missions and a new ESA mission is heading towards Venus towards the end of the decade.

Of course, there are some caveats. “We’re going to base our discussions about life on other worlds on what we know about life on Earth, so we have a basis for that,” McKay says. “But part of me hopes that when we find life elsewhere, it’s really very, very different,” with biochemistry working beyond the limits of what we’ve seen here on Earth.

And even if the current life on Venus might seem unlikely with these new discoveries, it doesn’t mean that Venus has always been sterile. There is a whole hidden story on the planet that scientists want to investigate.