There is not enough water in the clouds of Venus to sustain life

In 1978, NASA launched the Pioneer Venus mission, which consisted of an orbiter and a group of four small probes that were thrown into the atmosphere of Venus. There are signs of deuterium in the atmosphere-a heavy isotope of hydrogen produced by the decomposition of water. Scientists want to know whether Venus was once home to large amounts of water, and whether some really retained large amounts of water in the atmosphere.

Fast forward to 2020, may detect Traces of Phosphine In the atmosphere of Venus.Those scientists Imagine a scene Understand how the potential water cycle in the Venus sulfuric acid heavy cloud allows the microorganisms on Venus to exist in high-altitude droplets and produce spores that can hydrate and maintain the reproductive life cycle. Although the surface of this planet is hell, its clouds are stable and milder.

Well, the new paper means this is unlikely. The focus of the study is “water activity”, which is the amount of water available to microorganisms, measured in the range of 0 to 1. In this study, the research team tried to measure the water activity humidity (the amount of water that saturates the air at a given temperature) in the cloud by calculating the relative humidity of the atmosphere.Scientists used Aspergillus penicillium, A fungus that can live in some of the driest conditions imaginable, serving as a baseline for understanding how much water an organism can tolerate while still being able to perform metabolic functions and reproduce. The answer is a water activity score of 0.585-as we know, this is actually the “life limit” of biological activity.

Hallsworth and his team used atmospheric data collected from past Venus missions and used updated models to assess water activity. They calculated the water activity of the Venus cloud at an altitude of 68-42 kilometers, where the temperature tolerance of life is in the range of − 40°C to 130°C. They found that the water activity is at most 0.004. “The most drought-tolerant microorganisms on earth have no chance on Venus,” Holsworth said.

The researchers also pointed out that even if the water activity itself is higher, the atmosphere of Venus is full of harmful elements that may hinder the normal operation of the cell system (for example, sulfuric acid dehydrates cells).

Other planets perform better. The team also calculated that the water activity in the Martian cloud is 0.537 (compared to the Earth’s stratosphere, only slightly lower than the “life limit” of life on Earth), while in the Jupiter cloud, where the temperature is lower , It happens to be at least 0.585. Between -10°C and 40°C. “We cannot say that Jupiter’s clouds are habitable,” said Christopher McKay, a NASA scientist and co-author of the study. “We can say that they are not limited by water activity.”

These findings need to be confirmed by more studies, but the author is very confident that this will not change, even if Two new NASA missions A new ESA mission is heading to Venus at the end of the century.

Of course, there are some caveats. “We must discuss life in other worlds based on our understanding of life on earth, because we have a foundation,” McKay said. “But some parts of me hope that when we do find life elsewhere, it’s really very, very different.” The role of biochemistry is beyond the limits we see on Earth.

Although based on these new discoveries, the current life of Venus seems unlikely, but this does not mean that Venus is always barren. Scientists want to investigate the entire hidden history of this planet.