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But what are we looking for on the planet Mars?

2021-02-28T06:20:05.523Z


Perseverance is the latest in a long, far from over, series of space missions to auscultate the red planet.


Why does a hostile planet located tens of millions of kilometers fascinate us so much?

While three space missions come in quick succession to reach the planet Mars, we take stock of the scientific answers we came to seek there.

Some water ?

No… because we have already found some.

"The quest for life elsewhere and the understanding of its appearance on Earth, the ultimate objectives of space exploration, begin with the search for water", recalls Pernelle Bernardi, engineer at the Laboratory for Space Studies and Astrophysics Instrumentation (Lesia) in Paris, and technical manager on the Perseverance mission.

Hydrated minerals, clays, ice, and even tiny amounts of liquid water: the evidence gleaned over the past decades is plentiful, but water is not enough to make a planet habitable: “You need an atmosphere and a magnetic field to protect from cosmic rays, and traces of certain elements favorable to life.

There again, several missions, including the incredible epic of Curiosity, at the beginning of the 2010s, took up the gauntlet.

We now know that a very long time ago, between 3.5 and 4 million years ago, Mars could have resembled our Earth.

Martians?

If Mars was once habitable, this is no longer the case today.

The atmosphere has almost disappeared, the liquid water too.

"If we find living Martian microorganisms, that's very good, but it means that they really managed to survive in a very very hostile environment", smiles Athena Coustenis, also a researcher at the CNRS and president of the Committee of evaluation on research and space exploration at CNES.

“No, what we are really looking for today are traces of past life.

" But still ?

"We know that life favors certain geometries of molecules, we know how to recognize them," says Pernelle Bernardi.

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Perseverance: why listen to the sound of the planet Mars?

To carry out this mission, we therefore rebuilt a state-of-the-art “Curiosity”, Perseverance, and we dropped it in the middle of the delta of an old river, clad with cutting-edge instruments: an infrared laser responsible for heating and analyzing la roche (the famous French Supercam), a dragonfly mini-drone responsible for experimenting with autonomous flight, and above all a system capable for the first time of "drilling cores several centimeters" under the surface.

And to store these little memories while waiting for the cavalry to arrive in five years, during a formidable European-American mission, Mars Sample Return, dedicated to bringing the samples back to Earth.

“Our analysis capabilities on Earth are incomparable with the instruments on board Mars,” explains Athena Coustenis, working on MSR.

Especially that "by the return of the samples, in 10 years, we have time to perfect our laboratory experiments and our reception facilities".

Our future ?

Let's imagine that our little Indiana Jones, mechanic version, and his little European sister Rosalind Franklin, who is due to take off in two years, fulfill their mission and find the Grail.

What would that mean?

“The Earth is currently the only example of a planet that works, that heats up but degasses enough to create the conditions for life,” explains Benoit Langlais, researcher at the Laboratory of Planetology and Geodynamics in Nantes.

So we would have another example of a planet ... which worked.

Imagine two saucepans of hot water: one boils over a lit fire, it is Earth.

The other is still hot but is cooling because the fire has gone out.

It's Mars.

"

What happened ?

And would the past of the red planet be the future of the blue planet?

"Honestly, we do not know anything", admits the researcher, who puts forward hypotheses: "Mars, twice smaller than the Earth, could have burned all its fuel.

A surface that was too dense could also have prevented it from dissipating heat properly and from running at full speed.

»Is it possible in this second scenario that a dangerous surplus of heat is trapped there?

"It did not happen like that on Mars, but undoubtedly on Venus, the hypothetical theater of a sudden period of intense volcanism which led to a great resurfacing".

A nice euphemism for the apocalypse.

"My field of study often makes it possible to better estimate the chance that one has to be on Earth", philosopher the scientist.

A human destination?

On this last question, which is not the least, opinions differ.

"In absolute terms, and for strictly scientific purposes, a man on Mars will have a much richer perception than a robot", for Pernelle Bernardi.

But for her colleague Athéna Coustenis, "it is not justifiable, except to study man".

His arguments are not lacking: "A manned mission costs up to 100 times more expensive, the cost of an accident (Editor's note: today, one mission in two does not arrive on Mars) would be invaluable, and even if you To get there, we would have to find a way - without contaminating anything - to create a biosphere from the resources on site, which we cannot even do on Earth, so when I hear Elon Musk, I laugh!

".

But she dreams of it too.

"It's paradoxical, but we can't help dreaming about it, it's like that in our field ... You know, we have proven for years that living in space is not good at all for health, but we continue to go and check it permanently in the ISS ”…

Also to discover: our “Rêves de Mars” series in four episodes:

  • Goodbye planet A, direction planet B?

  • Expat life, millions of kilometers away

  • 100,000 years to recreate the Earth

  • Explore time, search for life

Source: leparis

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