The amount of water in Venus’ atmosphere is so small that even the most drought-tolerant microbes on earth couldn’t survive there, a new study found. The results seem to destroy the hope raised by the discovery of molecules last year that may have been produced by living organisms in the atmosphere of the scorched planet and that were seen as indicative of the possible presence of life.
The new study looked at measurements from probes flying through Venus’ atmosphere and collected data on temperature, humidity, and pressure in the thick clouds of sulfuric acid that surround the planet. From these values, the scientists were able to calculate the so-called water activity, the water vapor pressure within the individual molecules in the clouds, which is one of the limiting factors for the existence of life on earth.
“When we examined the effective concentration of water molecules in these clouds, we found that it was a hundred times too low for even the most resilient earth organisms to survive.” John Hallsworth, microbiologist at Queen’s University in Belfast, UK, and lead author of the Papiers said on Thursday (June 24th) at a press conference. “That is an unbridgeable distance.”
The results are likely a disappointment to the Venus research community, which was enlivened last September by the discovery of phosphine, a compound of phosphorus and hydrogen atoms that can be linked to living organisms on Earth, in Venus’s atmosphere. At the time, researchers suspected that the phosphines could be produced by microorganisms that live in these clouds.
On earth, according to Hallsworth, microorganisms can survive and multiply in water droplets in the atmosphere if temperatures allow. However, the results of the new study, which is based on data from several Venus probes, leave no chance that anything is living in the clouds of Venus, he said.
“Living systems, including microorganisms, are primarily made up of water and without hydration cannot be active or reproduce,” said Hallsworth.
Studies of microorganisms that live under extreme conditions on earth have shown that life can exist at temperatures as low as minus 40 degrees Fahrenheit (minus 40 degrees Celsius). For water activity, which is measured on a scale from 0 to 1, the lowest survival value is 0.585. The water activity of the molecules in the Venus clouds was only 0.004.
NASA Ames astrobiologist Chris McKay, one of the co-authors of the paper, said at the press conference that the results of the study were conclusive and that the new fleet of space missions currently being prepared for Venus lacked hope of life will change with the closest neighbor on earth.
“Our conclusion is based directly on measurements,” McKay said in the briefing. “It’s not a model, it’s not an assumption. The missions NASA has just selected for Venus will do the same measurements again – temperature, pressure – and they will come to the same conclusions since Venus does not change on this type of timescale. “
However, the researchers also examined data from other planets and found that Jupiter’s clouds provide enough water activity to theoretically support life. Data collected by the Galileo probe at altitudes between 42 and 68 kilometers above the surface of the gas giant suggest that the water activity value is at 0.585, just above the survival threshold. The temperatures in this region can barely survive at around minus 40 degrees F.
“Jupiter looks a lot more optimistic,” McKay said. “In the clouds of Jupiter there is at least one layer in which the need for water is met. It doesn’t mean there is life, it just means that it would be fine with respect to water. “
However, high levels of ultraviolet radiation or a lack of nutrients could prevent potential life from flourishing, the researchers said, and entirely new measurements are needed to find out whether or not it might actually be there.
Hallsworth added that the method of calculating water activity could also help determine the habitability of exoplanets.
“What excites me most is that for these distant planets we can go on the water molecule scale and determine their potential habitability,” said Hallsworth.
The results are described in an article published June 28 in the journal Nature Astronomy.
Copyright 2021 Space.com, a company of the future. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.