New research says liquid water is unlikely to be found on Mars anytime soon

More than 100 years ago, astronomer Percival Lowell proposed the existence of canals on Mars designed to redistribute water from the planet’s ice sheets to lower, drier latitudes. This necessarily meant the presence of Mars building canals.

Although better telescopes have proven Lowell’s idea wrong, the question of whether liquid water exists on Mars continues to vex researchers. Liquid water is an important prerequisite for a habitable planet. However, the combination of Mars’ low temperatures, atmospheric pressure, and water vapor pressure means that any liquid water found on Mars would likely freeze, boil, or evaporate quickly, making it unlikely that Mars exists. .

Still, researchers continue to insist that liquid water exists on Mars.

Of particular interest is the discovery of “repeating slope lines” (RSLs), dark linear features found on steep slopes in certain regions of Mars. RSL displays seasonal changes that appear in the warm season and disappear in the cold season in a manner consistent with the behavior of liquid water. Distinctive striped and polygonal features in Martian permafrost have also been pointed to as possible evidence of thermal cycles. In addition, cases have been made for the possibilities of different liquid brines.

But a new paper published in the Proceedings of the National Academy of Sciences pours cold water on the idea that liquid water is likely to be found soon in Mars’ RSL, permafrost, or salt water.

The paper, “The Elusive Properties of Liquid Salt Water on Mars,” was co-authored by Vincent Chevrier, an associate research professor at the University of Arkansas Center for Space and Planetary Science, and Rachel Srank, a postdoctoral fellow at the Lunar and Planetary Institute. . in Houston, Texas. Srank received his Ph.D. at the University of California, in collaboration with Chevrier, who has been studying signs of liquid water on Mars for the past 20 years. In other words, he’s as interested as everyone else in the existence of liquid water on Mars, but he thinks the evidence for it just hasn’t been found yet.

The purpose of this paper is to educate the public about the current state of knowledge regarding the presence of liquid water on Mars.

“I’ve wanted to write this paper for a long time,” Chevrier said. Liquid water on Mars. ”

The authors suggest that close observation of RSLs shows that their behavior is consistent with sand and dust flows, and that water is not required for RSL formation. Data available from Mars rovers do not confirm that liquid water plays any role in RSL development.

Other researchers believe that brine, a highly salty solution like Earth’s oceans, may hold the key to finding liquid water on Mars. Salt water can freeze at much lower temperatures, and Mars is rich in salt. Among these salts, perchlorate appears to be the most promising because of its extremely low eutectic temperature (the temperature at which the melting point of the mixture is lower than that of the single components).

For example, calcium perchlorate brine freezes at -75 degrees Celsius, but the average surface temperature near the equator of Mars is -50 degrees, so theoretically calcium perchlorate brine, especially underground, could remain liquid. It suggests that there may be zones where .

The authors then consider all the arguments for and against brine that could form a stable liquid. Ultimately, they concluded that a variety of limiting factors, including the relatively small amount of most promising salts, water vapor pressure, and ice location, “significantly limit the abundance of surface or shallow subsurface brine.” I concluded. Even if saline waters formed, they would “remain highly uninhabitable by terrestrial standards.”

In the final section of the paper, the authors write, “Despite these shortcomings and limitations, there is always a possibility that Martian life and some terrestrial organisms adapted to these salt waters could survive in them; is a planetary protection consideration. In that case, detecting brine in situ remains a key objective of Red Planet exploration, as Mars may exist today.”

The next hurdles ahead, the authors say, are improving the equipment needed to detect small amounts of brine, better identifying the best places to look for brine, and conducting more experiments under Martian conditions. It is suggested that this is to enable room measurements to be carried out.

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