Why the discovery of underground saltwater lakes is extraordinary

The planet Mars in 2001, seen by the Hubble telescope.

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• A team of Italian researchers has discovered four saltwater lakes below the surface of the South Pole of Mars.

• Scientists had already revealed the presence of the largest of the lakes in 2018, but its existence had been questioned by the scientific community for lack of sufficient data.

• According to Léa Griton, doctor in astrophysics, researcher at the Institute for Research in Astrophysics and Planetology (IRAP / CNRS), this discovery is a "step closer to the proof of life on Mars".

An "extraordinary" find.

Two years after the discovery of an underground lake on Mars, Italian scientists have confirmed its existence, but they have also spotted three other pockets of water, they revealed in a study published in the journal

Monday.

How many lakes are there on Mars?

Why is this discovery so important?

What exactly are scientists looking for? 

takes stock.

• What have the scientists discovered?

In 2018, researchers from the University of Rome III announced that they had discovered a saltwater lake under the ice at the South Pole of Mars, in a region called Planum Australe.

If this announcement seemed promising, it had nevertheless been greeted with skepticism within the international scientific community.

In question: the small amount of data on which the researchers relied to support this assertion - 29 observations between 2012 and 2015. “At the time, we considered that there were not enough measurements to be certain of this discovery ”, explains Léa Griton, doctor in astrophysics, researcher at the Institute for Research in Astrophysics and Planetology (IRAP / CNRS), at

.

But today, Italian scientists may well end up convincing their colleagues.

“The team collected more data.

Not only did they find the lake discovered two years ago, but in addition, they spotted three other lakes, ”explains Léa Griton.

Led by Sebastian Emanuel Lauro, researcher at the University of Rome III, the team relied on data from the European orbiter Mars Express, as well as 134 additional observations made from 2012 to 2019.

• How is the data collected?

If no man has set foot on the Red Planet yet, how did scientists come to identify these bodies of water?

The team used a radar instrument called 

(Marsis), to probe the south polar region of the planet.

“With this radar detection system, we send waves that bounce off Mars.

Depending on how these waves are reflected, we can identify the type of material, whether water, ice or rock, ”says the French astrophysicist, who specifies that this technique is already used on Earth. to identify underground glacial lakes.

And bingo, Italian scientists have detected areas of high reflexivity that show the presence of masses of liquid water trapped under more than a kilometer of ice.

According to planetologists, these four lakes lie 1.5 kilometers below the surface of Mars.

The largest, discovered in 2018, measures 30 kilometers in diameter.

The other three are each a few kilometers wide.

According to them, if the water does not freeze, it is thanks to its very high salinity.

In other words, they would be saltwater lakes.

• Why is this an “extraordinary” discovery?

According to researcher Léa Griton, this discovery is a first step towards proof of life on Mars.

“We know that water is a key, essential ingredient in life.

If we find water in liquid form, it means that potentially there may have been life on Mars.

And that is extraordinary.

"For the specialist, this study could also allow the scientific community to advance research on planets other than Mars:" Water is a key ingredient, but that's not all.

Once we have found water, we can take care of the other factors that allow, or not, life on the other planets of the solar system, but also on other exoplanets.

"

And the adventure is not over yet.

In June, NASA, the US space agency, sent a robot, named Perseverance, into space, which should land on Mars in February 2021. The goal?

Explore the red planet and look for traces of life there.

“He's going to collect samples that he's going to drop off somewhere else on Mars, easier to access.

Another mission will then come to collect these samples to bring them back to Earth in laboratories which will analyze them and look for traces of life ”, continues Léa Griton who hopes that the results“ will motivate even more ambitious space missions ”.

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