What does the detection of phosphine in the atmosphere of Venus mean?
A photo of the planet Venus taken by NASA on June 5, 2012. (Illustration).
REUTERS
Text by: Simon Rozé Follow
8 min
The presence of this gas in the atmosphere of our neighboring planet raises many questions as to its origin.
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In 24 hours, phosphine has never been so talked about.
The title of
the article published
by the journal
Nature Astronomy
did not, however,
herald
such a media
frenzy
: "
Gaseous phosphine in the high clouds of Venus
".
It was enough for the press releases to mention the fact that this molecule can be considered as a marker of the presence of life.
What is phosphine
It is a molecule made up of four atoms: a phosphorus and three hydrogens;
its scientific formula is therefore PH3.
On Earth, it is a poison for living things, except for anaerobic organisms, that is to say those which do not need oxygen.
These emit phosphine.
It is for this reason that it is considered as a possible “bio-signature”.
Its presence could indicate the existence of living beings, especially in
worlds devoid of oxygen
.
What have we detected on Venus?
An international team pointed two telescopes at Venus: the James Clerk Maxwell Telescope (JCMT) in Hawaii and Alma in Chile.
They used a technique called spectroscopy: "
We will look for the signatures in the light that is emitted by Venus
"
, explains Franck Selsis, CNRS researcher, specialist in the atmosphere of planets.
Certain colors of the white light emitted by the sun are indeed absorbed by the gases it passes through.
By analyzing this light, we can thus deduce the composition of the medium crossed: “
We will look for the fingerprint of a molecule through the absorption of light.
This is how we identify molecules in the cosmos or planetary atmospheres.
"
This is not the first time that we have detected phosphine in the atmosphere of another planet, it is the case of Jupiter for example.
On the other hand, as spectroscopy also makes it possible to "count" the molecules, the researchers were able to determine the abundance of them in the atmosphere of Venus: 20 parts per billion, that is to say 20 molecules per packet of billions analyzed. .
It doesn't sound like much, but it's actually abundant, and raises many questions about the origin of this phosphine.
After analyzing the data, the scientists determined that this phosphine was found in the clouds of Venus, at an altitude of about 50 to 60 kilometers.
If the ground of Venus is a hell charred by the greenhouse effect, at this altitude reigns a more temperate temperature close to 30 ° C.
However, it is an extremely acidic environment, which adds questions as to the origin of this phosphine:
"
It is a little surprising the phosphorus in this type of molecules
"
, explains Franck Selsis.
As on Jupiter,
“
we rather expect to find phosphine in environments rich in hydrogen, which are said to be reducing, while the atmosphere of Venus is oxidizing.
Its gases are very aggressive for a molecule like phosphine, which must therefore be quite unstable.
To explain its presence, we must therefore understand how it is formed
”.
BREAKING: Data from two ground-based telescopes have discovered small quantities of phosphine gas in the clouds of Venus.
There are no known non-biological mechanisms of making the gas on Venus, so it * may * be being produced by alien microbes.
(1/5) https://t.co/1quZTxibRJ pic.twitter.com/31EDjdWP9j
New Scientist (@newscientist) September 14, 2020
Where does this phosphine come from?
This is the big unanswered question raised by this study.
The researchers ruled out what they believed to be all known chemical means to explain the formation of this molecule.
Since phosphine can be emitted by anaerobic organisms, they do not exclude a biological origin, however being very careful: “
If this detection is confirmed, we insist on the fact that it does not constitute any robust proof of a presence of life, it just indicates unexplained chemistry
”
.
In fact, the atmosphere of Venus still holds many secrets.
“
It is extremely complex,
”
explains Franck Selsis.
“
We know the upper atmosphere fairly well, above the clouds, but they hide from us what is happening below.
And it's the bottom that determines what happens at the top
: volcanic activity, the exchanges between the surface and the atmosphere.
There are phenomena in the atmosphere of Venus that we do not fully understand.
There are very fast winds that make the clouds circle the planet in four days while its rotation is much slower than that.
There are sulfur molecules whose composition we do not understand very well, there is absorption of UV rays in clouds for which we do not know the chemical compound responsible.
"
It's everyone's dream to know if there is life elsewhere in the universe
David Elbaz, French astrophysicist, research director at the Commissariat à l'Énergie atomique
Therefore, before considering possible Venusians, it is advisable to better understand this planet: "
At this stage there is no reason to invoke any biological process in the discovery of phosphine
", insists Franck Selsis.
“
We cannot link life to an atmosphere of which we do not understand basic physical mechanisms
”.
To see more clearly, it will therefore be necessary to deepen research.
Long neglected in favor of Mars by space programs, Venus nonetheless interests more and more and several projects are under study.
"
Venus is a key in particular to understanding the history of the Earth
", advances Franck Selsis.
“
It's a planet similar to ours which had a completely different destiny.
It is very interesting to understand why carbon dioxide has accumulated there in this super greenhouse effect.
"
A new question has therefore been added to this long list, and it will still take time to understand the origin of the phosphine of Venus.
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