In a few hours, hypothetical Venusians came to supplant the traditional Martians in the media imagination.
"Life on Venus?" Asks the New York Times, while the venerable Massachusetts Institute of Technology (MIT) news site says "astronomers may have found a signature of the presence of life on Venus ".
This is due to a team of researchers from Cardiff University in the United Kingdom who observed traces of phosphine in the clouds of the second planet in the solar system.
Their discovery, published in the journal Nature Astronomy on Monday, September 14, was called "the most important event to date in the search for life outside the Earth", by Jim Bridenstine, administrator of NASA.
Venus, hostile to life
What is the relationship between this extremely flammable gas, highly toxic to humans, and life?
It is present on Earth as well as on other planets, such as Saturn or Jupiter, which however do not harbor any form of extraterrestrial life.
But the Venusian atmosphere is more like that of the Earth where "the presence of phosphine is always associated with living things", underlines Franck Montmessin, researcher at the Laboratory of atmospheres, environments, spatial observations (Latmos) of the CNRS, contacted by France 24. He There are two types of atmosphere, explains this researcher: that of planets like Jupiter, whose "chemical processes are rather favorable to the subsistence of this gas", and that of the Earth or Venus - called oxidizing atmosphere -, which does not is not.
In the latter case, the presence of phosphine on the surface is the result of biological activities.
It must be expelled regularly by organisms to continue to remain noticeable in the atmosphere.
On Earth, phosphine is also used in industry, such as in the manufacture of semiconductors.
The possible implications of the discovery of traces of this gas in Venusian clouds has taken the scientific community all the more by surprise since this planet is not on the radars of alien life seekers.
On the contrary: "We could cite it as a counter-example of what a living habitat could be", even says Franck Montmessin.
The atmosphere there is 95% carbon dioxide, which means that there is a surface temperature of over 450 ° C, while the clouds are made up of over 90% sulfuric acid, so highly toxic.
Not to mention that the atmospheric pressure is about 100 times higher than on Earth.
"Venus is the most extreme example of what the Earth could eventually become because of global warming", summarizes Franck Montmessin.
It's hard to imagine a more improbable place to locate the first signs of extraterrestrial life.
Except to adhere to hypotheses developed in the 1960s by a handful of scientists, like the American biophysicist Harold Morowitz, who maintained that life could be possible in… the clouds of Venus.
Avoid premature conclusions
This is precisely where the traces of phosphine were detected by the two radio telescopes of researchers at Cardiff University.
The idea, to summarize, is "that it is less hot there than on the surface, and that there are examples of living organisms which have been able to adapt to extreme conditions", specifies Franck Montmessin.
On Earth, for example, scientists from NASA had identified, in 2010, a bacterium capable of living in a lake where the concentration of arsenic was very high.
But it would still be premature to trumpet that humanity is on the cusp of an encounter of the third kind.
First, it would be necessary "to be able to confirm this first detection", underlines the researcher of Latmos.
In this type of work, "we flirt with the limits of observation", and even if researchers at Cardiff University seem to have taken all precautions, an error of interpretation can never be ruled out. he.
A confirmed presence of phosphine in the atmosphere of Venus would not, then, certainly be proof of the existence of life, nestled in the heart of the planet's cumulus clouds.
If on Earth, the oxidizing effect of the atmosphere destroys the phosphine produced by the planet, there may, for example, be a still unknown mechanism that would prevent this phenomenon on Venus.
To put an end to this story, it would therefore be necessary to go there to take surveys.
A trip that in itself would only last a few months, Venus being a little closer to Earth than Mars.
But the preparation of such an expedition would take several years.
Then the readings should be brought back to Earth to undergo a battery of examinations to solve the mystery of Venus' phosphine once and for all.
A long-term undertaking, but one that would be worth it ... even beyond the search for any trace of extraterrestrial life.
“There have only been three missions to Venus in the past 30 years,” recalls Franck Montmessin.
An opinion shared by Jim Bridenstine, the administrator of NASA, who pointed out that this observation shows that our neighbor in the solar system still has a lot to teach us and that it is "time to give priority to Venus".
After all, the planet has long been called Earth's "twin sister" (because of similarities in the atmosphere), and one should not neglect his family for so long, especially if they can turn out to be more alive than they are. didn't think so.
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