No life possible on Venus, for lack of water

There is no possible active life in the clouds of Venus, microbiologist John Hallsworth, lead co-author of the study published Monday in Monday, said in a press briefing. Nature Astronomy.

The closest neighbor to Earth resembles it in many ways, in size and mass, but is distinguished by an infernal surface temperature, 470 C °, and a carbon dioxide atmosphere at 97%. In other words, not very conducive to life.

The planet is also covered with a thick layer of clouds made up of droplets of sulfuric acid. It was in this that last September the British astronomer Jane Greaves announced the discovery of phosphine.

The phosphine coming, on Earth, from human or microbial activity, the announcement put the scientific community in turmoil. Before being vigorously contested by specialists who questioned the observation and the method used to conclude the presence of this gas.

Impassable distance

This time the objection comes to the very possibility that a living organism could exist under such conditions. One of the subjects of study of John Hallsworth, Queen’s University, Belfast, is the minimum quantity of water with which the most extreme microbes (the most resistant, Editor’s note) can be satisfied on Earth to remain active and develop.

His judgment is final: the quantity of water available in the clouds of Venus is more than a hundred times too weak for the survival of the most resilient microorganisms known. In other words, at an insurmountable distance from what life requires to function.

He drives the point home by adding: The most drought tolerant microbe would not have had a single chance in the clouds of Venus, and the most tolerant of an acidic environment even less.

Professor Jane Greaves’ team finally downgraded the amount of phosphine it claims to have detected. For Chris McKay, NASA astrophysicist and co-author of the study published on Monday, there is no firm consensus in the scientific community that the detected signal is phosphine.

But even if there is phosphine, we know the atmosphere of Venus sufficiently well, thanks to the probes which have flown over it, even crossed it, since the 1960s, and to observations from Earth, to tell if there is enough water for life, according to Chris McKay. And on Venus this is not the case, by far.

Realm of imagination

For this NASA expert, the three probes that will explore Venus around 2030 will confirm the temperature, pressure and water measurement data already acquired, while also making it possible to retrace the history of this neighbor. which could have been habitable three billion years ago.

But could the Star of the Shepherd, as it is called, harbor a different form of life than the ones we know? To this question philosophical, Chris McKay replies that then, we leave biology as we know it, and we enter the realm of the imagination.

If life is not possible on Venus, it may be on Jupiter, the second planet in our solar system to have, apart from Earth, a cloudy atmosphere. They offer a combination of the right temperature and water activity (its availability) to support an active life, according to Hallsworth. This is not enough, obviously, to affirm that it is present there.

With Chris McKay, they are banking on the next James Webb Space Telescope, which will take off in the fall, to explore the possibility of other planets that can harbor the living, by studying their atmosphere.