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Paris (AFP)
Researchers have concluded “an apparent presence” within the cloud layers on Venus of phosphine gas that is emitted on Earth by living creatures, in a discovery considered by the director of the United States Space Agency (NASA) as “the most important event “in the search for life outside Earth.
Jane Graves, a professor of astronomy at Cardiff University in Great Britain and author of the study, whose results were published this Monday in the journal Nature Astronomy, told AFP that it is the first time that this compound has been discovered on all four terrestrial planets. of the solar system, “except for planet Earth.”
Phosphine was discovered by observing the atmosphere of Venus with the help of two radio telescopes. It may come from “unknown pathways of photochemistry or terrestrial chemistry, or it may be similar to the biological pathway for phosphine production on Earth thanks to the presence of life.”
This compound is found in gas giants of the solar system, such as Saturn, but it has no biological origin, none of the sources associated with life forms. As for the traces of phosphine in the Earth’s atmosphere, it comes exclusively from organic or microbial activities.
Furthermore, the presence of phosphine, which is a highly toxic compound, does not conflict with the superheated atmosphere of the second closest planet to the sun. This planet, whose atmosphere consists of 97 percent carbon dioxide, is swimming at a surface temperature of around 470 degrees Celsius with a pressure ninety times greater than that found on Earth.
However, the phosphine molecules that the Graves-led research team concluded could be in the super-acid cloud layer around the planet at altitudes of up to 60 km.
In this position, the temperature of the clouds is “modified” in the limits of 30 degrees Celsius, according to the study, which does not rule out the formation of the gas at a lower altitude and higher temperature before ascending to the top.
– Evidence of life from Venus? –
But where does this gas come from? In answer to this question, Graves hopes that the study “takes into account all the paths that would explain its existence in the atmosphere of Venus.” Among these hypotheses is the possibility that the gas comes from some form of life.
And if this hypothesis is correct, “we see that (this form of life) can be of a reduced size that allows it to float freely”, according to the researcher, whose study highlighted that “monitoring of phosphine is not solid evidence of the existence of life, but of a chemistry outside of nature “. Interpretation of it “.
The study also notes that “the photochemistry of flower cloud droplets (from sulfuric acid) is completely unknown.”
Phosphine is made up of one phosphorus atom and three hydrogen atoms. Phosphorus is one of the six chemical elements for the emergence of life, but its presence on Venus does not necessarily mean the existence of life, according to Graves.
Graves said: “Even if a planet contains phosphorus in large quantities, it may lack another element necessary for life, such as the presence of other elements, or because its center is very hot or dry.”
– ‘The most important event’ –
NASA Administrator Jim Braidenstein was quick to welcome this discovery, calling it “the most important event” in the search for extraterrestrial life and calling for a diversion of the research from Mars to Venus.
“Life on Venus? The discovery of phosphine” is “the most significant event yet in the search for life outside of Earth,” Braidenstein said in a tweet on Twitter.
“It is time to prioritize Venus,” he added, rather than Mars, which to this day has focused most of the searches for life outside of Earth.
In addition, the astronomer at the University of Swinburne in Australia, Alan Duffy, explained that the discovery of the scientific team led by Graves was “one of the most exciting signs that I have seen of the potential existence of life outside the Earth”.
Scientists agree that the atmosphere of Venus is not, in principle, suitable for the emergence of life due to “extreme levels of dehydration and super acidity.” However, this observation may not be true for planetary clouds.
And NASA discovered a decade ago traces of microbial life in the upper layers of Earth’s atmosphere.
For this reason, Greaves and his team ask for a deeper observation of the phenomenon. This happens in the best of cases by the release of the “filter” of the Earth’s atmosphere by a space telescope, to be followed, perhaps, by a new visit of a probe to Venus or its atmosphere.
And it appears that the return of interest in this long-forgotten planet has become a general trend, as two of the four competing missions in NASA’s upcoming solar system exploration program are related to Venus, according to the scientific director of the agency, Thomas Zurbuken. The selection process should be completed next year.
© 2020 AFP
