One of the main objectives of the planetary exploration of Mars is the search for habitable conditions that would allow the existence of extraterrestrial life. And the presence of water is one of the essential conditions for life as we know it. For this reason, for decades the teams of scientists working in this field have devised dozens of strategies to detect the presence of water on the red planet both in the past and today. But very few works have been able to demonstrate that there is water flowing on the surface of Mars.

A few months ago, the Mars vehicle ‘Curiosity’ detected the first signs of liquid water in the first layers of the planet’s surface in the Gale Crater, results that were published in a study led by Spanish researchers. But on that occasion they could not directly see the hydrated salt rocks that the research spoke about, since they only occur at night and the rover does not work at those hours due to low temperatures, which range between 50 and 80 degrees below zero.

Now, another work led by researchers from the Georgia Institute of Technology (USA) has found new evidence of the presence of liquid water flowing on the surface of Mars today. But it’s not as simple as looking through a telescope and seeing rivers or waterfalls tumbling down Martian mountains. In the same way as in the work published thanks to the environmental analysis carried out by ‘Curiosity’, the researchers have found hydrated salts in mysterious elongated spots that appear on the slopes of the Martian surface during the summer of the red planet.

Researchers working on Mars have been wondering for years what might model those strange grooves that appear and disappear with the change of seasons. Until now they wondered if they were sand flows or carbon dioxide marks or perhaps water… The work recently published by the journal Nature Geosciences and led by Lujendra Ojha, a researcher at the Department of Earth and Atmospheric Sciences of the Institute of Georgia technology, finally settle the debate. Specifically, they analyzed four points on the planet where these types of grooves are produced, which the researchers call RSL, for the acronym in English for Sloping Recurring Lines: the Hale, Palikir, and Horowitz craters.

As the researchers have been able to demonstrate, these are salts -magnesium chlorates and magnesium and sodium perchlorates- hydrated by what the authors consider liquid water that circulates on the surface at present when the temperature on the planet is more favourable.” There has to be a water cycle on Mars,” the lead author of the study, Lujendra Ojha, told this newspaper. “The problem is that we still don’t understand it,” he acknowledges. The conclusions point in the same direction as the study carried out in Gale Crater, although, as Ojha points out, in a “less theoretical way through the discovery of perchlorates with traits of being in the presence of liquid water.

But it is not a discovery as it could be produced on Earth, directly. The researchers reached this conclusion after analyzing the spectral absorption of these materials present in the mysterious marks present on the steep slopes of Mars thanks to an instrument -a spectrometer- of NASA’s Mars Reconnaissance probe, which was able to recognize these perchlorates and chlorates in the infrared range.”The high concentration of salts makes this thick liquid not very volatile and lowers its freezing point by about 80 degrees, compared to that of pure water, which allows it to subsist in the liquid phase even in the extreme Martian conditions,” says astronomer Rafael Bachiller, director of the National Astronomical Observatory.

But where does that water come from?

“It is still not clear where that water comes from and what cycle it follows. Is it water that comes from the atmosphere? Or from the first layer below the surface? Or maybe it comes from an aquifer?” Ojha asks. For others colleagues, there are some theories that would be more plausible than others. “Mars could be geologically alive and that is very important for life”, comments the planetary geologist from the Institute of Geosciences (IGEO) of the Complutense University of Madrid and the CSIC Jesús Martínez Frías. “Geological activity modifies environments from a physical and chemical point of view and that can determine the conditions for habitability” says Martinez Frias.

Although the study by Ojha and his colleagues demonstrates the presence of liquid water – albeit in a short-lived way in terms of its duration on the surface – a possible environment for life would not take place on the surface. The ultraviolet radiation that exists on Mars would practically destroy any type of known organic matter. But that is not the only option.

In fact, a study carried out by the team of the Spanish researcher Martínez Frías himself has already shown that a very small thickness of some material such as basalt, gypsum or jarosite (all of them present on Mars) is needed to protect against radiation. to a possible candidate bacterium to inhabit under the surface of the red planet. “Although Curiosity has already made a hole, it would be necessary to be able to continue drilling the soil of the red planet to examine the material underground, because in the subsoil of the planet the conditions could be much more suitable than the surface ones to contain liquid water”, explains Bachiller.

However, to have irrefutable proof of both the presence of this possible flow of water under the Martian surface and of a possible form of life on Mars, it would practically be necessary that scientists can take these materials with their bare hands and drill into their surface. “And it’s something I hope to see with my own eyes,” says Martínez Frías. “It is possible that in the year 2030 or 2035 there will be a manned mission to Mars…”.

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