Scientists may want to lower expectations. A new study in the journal Nature Astronomy shows that there is not enough water on Venus to keep known life in the clouds alive.
”As we all know, life needs water.” John Halworth, a microbiologist at Queen’s University Belfast, who is also the lead author of the new study, said. The discovery shows that the water concentration in the clouds of Venus is “more than 100 times lower than the concentration required by the most resilient microorganisms on Earth.” An insurmountable distance. ”
In 1978, NASA launched the Pioneer Venus Project, consisting of an orbiter and a group of four small probes, deep into the atmosphere of Venus. Signs of deuterium-isotopes of hydrogen, also known as heavy hydrogen, were found in the atmosphere. It may be caused by the decomposition of water. Scientists want to know whether more water has ever existed on Venus, and whether some water existed in the atmosphere.
Fast forward to 2020, and potential traces of phosphine have been detected in the atmosphere of Venus. Scientists thus envisioned a scenario: the potential water cycle in Venus’s concentrated sulfuric acid clouds could allow microorganisms on Venus to survive in high-altitude water droplets and produce moist spores, thereby continuing the cycle of reproduction. Although the surface of Venus is like hell, its clouds are stable and gentle.
However, the latest research papers show that the probability of survival is very small. The focus of the study is “water activity”, which is the amount of water required by microorganisms, measured on a scale of 0 to 1.
In this study, the research team tried to measure the water activity in the clouds (the amount of water saturates the air at a certain temperature) by calculating the relative humidity in the atmosphere.
Scientists use Aspergillus flavatus (a fungus that lives in the driest conditions) to measure the minimum amount of water required by organisms, which can be used to maintain survival, maintain metabolic function and reproductive capacity. The result of water activity is 0.585, which is the “life limit” of biological activity known to mankind.
Halsworth and his team used atmospheric data collected from past Venus missions and new models to evaluate water activity. They calculated the water activity of the clouds of Venus at an altitude of 68-42 kilometers, where the temperature range suitable for life is minus 40 degrees Celsius to 130 degrees Celsius. They found that the water activity was only 0.004 at most. “Even the most drought-tolerant microorganisms on the planet can never survive on Venus,” Halsworth said.
The researchers also pointed out that even if the water activity itself is higher, the atmosphere of Venus is still full of unfavorable elements, which may hinder the normal operation of the cell system (for example, sulfuric acid can dehydrate cells).
The situation on other planets is better. The research team also calculated that the water activity in the Martian clouds is 0.537 (equivalent to the Earth’s stratosphere, only slightly lower than the “life limit” of life on Earth), while in the Jupiter clouds, the temperature is between 10 degrees Celsius and minus 40 degrees Celsius. The water activity between degrees Celsius is at least 0.585.
”We can’t say that Jupiter’s clouds are habitable,” said NASA scientist Christopher McKay, who is also one of the co-authors of the study. “We can say that they are not limited by water activity.”
These findings More research is needed to confirm, but the authors firmly believe that this will not change. Although at the end of 2020, there are two new NASA missions and a new ESA mission to Venus.
Of course, there are some warnings. “Our discussion of extraterrestrial life must be based on our understanding of life on Earth, because this is our foundation,” McKay said. “But deep in my heart, I hope that when we really find life elsewhere, it is It’s really very, very different from earth’s living things” because the role of biochemistry is beyond what we see on earth.
Although these new discoveries seem to make people feel that Venus is not very livable at present, it does not mean that Venus will always be a barren land. Scientists want to delve into the entire history hidden behind this planet.