Traces of life on Venus? "We are very far from that"

What if the planet Venus contained traces of life?

British and American scientists raised this hypothesis in an article published Monday in the journal

.

The researchers claim to have discovered the presence of a toxic gas, phosphine, which could well be the consequence of a form of life.

But several scientists expressed their skepticism after the announcement.

Planetologist François Forget, research director at CNRS, called for caution on Tuesday morning on Europe 1. "One of the gurus of our specialty, an American called Carl Sagan, had said that an extraordinary statement, like the announcement of life on Venus, 'asks for extraordinary proof'. We are very far from it, ”he said.

Traces of phosphine "in very small quantities"

Researchers have discovered a poisonous gas, phosphine, in the cloud layers of Venus.

They are found on Earth in small quantities, including swamps, wet water or manure.

According to scientists, the presence of this compound could, as on our planet, come from a form of life.

But for François Forget, the quantities of phosphine discovered on Venus remain too limited to draw any conclusions.

"For the moment, it is extremely speculative on two counts. First question which one asks: is the detection (of phosphine) valid?", Wonders the planetologist, whereas the phosphine was discovered by observing the Venusian atmosphere using two radio telescopes.

"There, we detected very small quantities. We are really at the limit of what we can do with the instruments. I know colleagues, specialists in this detection method, who are skeptical and do not believe it" , he assures.  

>> Find Matthieu Belliard's interview in replay and podcast here 

Venus, an "inhospitable" planet where "nothing survives"

So far, nothing hinted at a potential form of life on Venus, a planet where the surface temperature exceeds 450 degrees, "very inhospitable" and where "nothing survives".

"But if we go up in altitude, it is a little colder and around 50-60 km, we have a thick layer of clouds there. The pressure is roughly like on Earth and the temperature there is 0, 30 or 50 degrees ", details the planetologist.

"And there we have droplets in the clouds. They are not water droplets, but rather sulfuric acid with a little water. In this environment, for many years now, we have speculated that certain very particular terrestrial bacteria, those which are able to live in extremely acidic conditions, could survive, "he continues.

“Another hypothesis is that Venus, which today is a hell especially on the surface, must have looked more like Earth a few billion years ago. There was perhaps an ocean on Venus, life has maybe emerged around that time under much more favorable conditions, and maybe she survived in those clouds. It's crazy speculation that remains to be proven, "he warns.

"Not a robust proof of life"

So where could this phosphine come from?

The scientists behind the announcement "have considered all kinds of possibilities, like lightning in clouds, volcanism, but nothing works. So what can it be? On Earth, phosphine is produced by life, so on Venus it may also be life ", explains the planetologist.

The authors of the study also agreed and insisted "on the fact that the detection of phosphine is not a robust proof of life, only of an abnormal and unexplained chemistry".

Send a probe to verify this hypothesis?

To support their hypothesis, the scientists behind this discovery argue for further observation of the phenomenon, either through a space telescope or by sending a probe.

Several exploration projects of Venus are currently under study, as François Forget recalled.

Thus, two of the four missions competing for the next NASA solar system exploration program concern this planet.

The European Space Agency (ESA) is also studying the advisability of sending a mission to Venus.

"We have in our boxes a collaboration with the Indians, who have the project to send a mission around Venus. We have the idea, with Russian colleagues, to send a spectrometer capable of making a very precise detection, to to prove or not the presence of phosphine ", argued the planetologist.

The race to explore Venus has only just begun.