Researchers have established the “apparent presence“in the cloud layers of Venus of a gas which on Earth is associated with life, a discovery described by the head of NASA as “most important event“in the search for extraterrestrial life.
The discovery, led by an astronomer at Cardiff University in the UK, was published Monday in the journal Nature Astronomy.
This is the first time that this compound has been discovered in one of the four terrestrial planets of our solar system, “the earth apart“Jane S. Greaves, professor of astronomy and lead author of the article, told AFP.
Phosphine was detected by observing the Venusian atmosphere using two radio telescopes. She “could come from unknown processes of photochemistry or geochemistry, or, by analogy with the biological production of phosphine on Earth, thanks to the presence of life“, explains the study.
This compound is found in the giant gas planets of the solar system, such as Saturn, but it is not of biological origin, that is to say of living. The traces of phosphine present in the Earth’s atmosphere, on the other hand, come exclusively from human or microbial activity.
Priority to Venus!
“Of life on Venus? The discovery of phosphine, a by-product of anaerobic biology, is the most significant event to date in the search for life outside of Earth“, rejoiced Jim Bridenstine, administrator of NASA.
“It’s time to put Venus first“, he launched, while the past life research missions focus today on Mars, assailed by American probes and robots and others.
For Professor Alan Duffy, an astronomer at Swinburne University in Australia, the discovery is “one of the most exciting signs I have ever seen of the possible presence of life outside of Earth“.
The presence of phosphine, a highly toxic compound, does not mismatch in the hellish atmosphere of the second planet closest to the sun. Also known as the Shepherd’s Star, its atmosphere of carbon dioxide, at 97%, bathes in a surface temperature of around 470 ° C with a pressure more than 90 times greater than ours.
But it is in the thick layer of hyper acidic clouds, covering the planet up to around 60 km of altitude, that the team of Jane Greaves supposes that the molecules of phosphine can be found.
“There the clouds are ‘temperate’ around 30 degrees Celsius“, according to the study, which does not exclude that the gas forms at a lower and warmer altitude before rising.
A small life form?
But where does it come from? Prof. Greaves “hopes to have taken into account all the processes that may explain its presence in the atmosphere of Venus“Unless you identify a new one, there remains the hypothesis of a form of life.
If that is the case, “we think (this life form) should be small, to float freely“, explains the scientist, whose study”insists that the detection of phosphine is not robust proof of life, only abnormal and unexplained chemistry“.
Phosphine is made up of one atom of phosphorus and three of hydrogen. Phosphorus is one of the six chemical elements of living things, but “even if a planet contained an abundance of phosphorus, it could be missing another condition necessary for life, such as other elements, or its environment could be too hot, or too dry“, warns Jane Greaves.
A priori, the atmosphere of Venus, “extremely dehydrating and hyper acidic“, is not conducive to life. But maybe its cloud cover could be.
NASA also discovered a decade ago microbial life in the upper layers of the Earth’s atmosphere.
This is why Pr. Greaves and her colleagues are calling for a more in-depth observation of the phenomenon. Ideally free from “filtered“of the Earth’s atmosphere, thanks to a space telescope. And why not with a new visit, by probe.
The renewed interest in this long neglected planet is general: two of the four missions competing for the next exploration program of the NASA solar system concern Venus, recalled Thomas Zurbuchen, scientific director of the agency. The selection will take place next year.