Mars, the name itself sparks a lot of curiosity among humans who have been captivated by the reddish hue that distinguishes the planet from its shimmering siblings. Scientists have been trying to explore Martian soil since the 1960s and we want to know if it has ever harbored extraterrestrial life.

With all the space organizations working day in and day out, we often come across different reports or studies about the red planet. The latest was in August 2024, when a study revealed that scientists had discovered a reservoir of liquid water on Mars, deep in the planet’s rocky outer crust.

However, this was not the first time: over a hundred years ago, astronomer Percival Lowell argued for the existence of canals on Mars designed to redistribute water from Martian ice caps to its higher latitudes. lower and drier. This necessarily meant the existence of Martians to build the canals.

Difficult for water to exist in its original form

Dark surface features called recurring slope lines (RSL), polygonal formations in Martian permafrost, and the possibility of liquid brines have fueled discussions of liquid water on Martian soil. Although the combination of low temperatures, atmospheric pressure and water vapor pressure on Mars makes it difficult for water to exist in its true form, i.e. in a liquid state , scientists continue to guarantee the presence of liquid water on the planet.

However, a new study, published in the Proceedings of the National Academy of Sciences, suggests that the presence of liquid water on Mars is much less likely than expected.

The paper, “The elusive nature of Martian liquid brines,” was co-authored by Vincent Chevrier, associate research professor at the University of Arkansas Center for Space and Planetary Sciences, and Rachel Slank, postdoctoral fellow at Lunar and Planetary. Institute in Houston, Texas. The objective of the article is to inform the public about the current state of knowledge regarding the existence of liquid water on Mars.

“A lot of confusion, a lot of misunderstanding”

Chevrier, who has spent the last 20 years studying Mars for signs of liquid water, said: “I’ve wanted to write this article for a very long time.” Explaining why he wrote the article, he added: “I think there is a lot of confusion, a lot of misunderstanding and a lot of misinterpretation of what the research papers say about the state of the “liquid water on Mars.” Chevrier is as invested as anyone in the presence of liquid water on Mars, but he thinks the evidence just isn’t there yet.

The researchers revealed that closer observation of the RSLs indicated that their behavior is consistent with flows of sand and dust without the need for water to create them. The data available from Mars orbiters also cannot confirm that liquid water plays any role in the development of the RSL.

Other researchers believe that existing brines, which are solutions with high salt concentrations, like those in Earth’s oceans, could hold the key to finding liquid water on Mars.

According to a study, brines can freeze at much lower temperatures and there is an abundance of salts on Mars. Of these salts, perchlorates appear to be the most promising, because they have extremely low eutectic temperatures (that is, when the melting point of a mixture is lower than that of any individual ingredient).

For example, a calcium perchlorate brine solidifies at -75 degrees Celsius, while Mars has an average surface temperature of -50°C at the equator, theoretically suggesting that there could be an area where the Calcium perchlorate brine might remain liquid, especially in the basement.

After considering all the arguments for and against brines that could form stable liquids, Chevrier and Slank concluded that the various limiting factors, including the relatively small quantities of the most promising salts, the pressure of water vapor and the location of the ice “strongly limits the abundances of brines on the surface or shallow subsurface. Even if brines formed, the researchers believe they would “remain highly uninhabitable by Earth standards.”

Major goal of Mars exploration

In the final section of the latest study, the researchers said: “Despite these drawbacks and limitations, there is still the possibility that Martian life adapted to these brines and that some terrestrial organisms could survive in them, which is a consideration for the planetary protection because life on Mars could exist today in this case. The detection of brines in situ therefore remains a major objective in the exploration of the Red Planet.

Additionally, the authors suggested that the next step would require improved instruments to detect small amounts of brines, a better job of identifying the best places to look for them, and the ability to perform more laboratory measurements in Martian conditions. .

“Despite our best efforts to prove otherwise,” Chevrier concluded, “Mars still remains a cold, dry and completely uninhabitable desert.”