Mars, the name itself creates a lot of curiosity among humans who have been captivated by the reddish hue that places the planet apart from its shimmering siblings. Scientists have been trying to explore the Martian soil ever since the 1960s and we have been quite keen to know if it has ever hosted alien life.
With all the space organisations working day in and day out, we often come across different news reports or studies about the Red Planet. The latest one was in August 2024, when a study revealed that scientists have discovered a reservoir of liquid water on Mars - deep in the rocky outer crust of the planet.
However, it was not the first time as more than a hundred years ago, astronomer Percival Lowell had made the case for the existence of canals on Mars designed to redistribute water from the Martian ice caps to its lower, drier latitudes. 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 lineae (RSL), polygonal formations in Martian permafrost, and the possibility of liquid brines have fuelled discussions about liquid water on the Martian soil. Though the combination of low temperature, atmospheric pressure and water vapor pressure on Mars makes it difficult for water to exist in its actual form i.e. in liquid state, scientists continued to vouch for the presence of liquid water on the planet.
However, a new study, published in the Proceedings of the National Academy of Sciences, suggested that liquid water on Mars is far less likely than hoped.
The paper titled, "The Elusive Nature of Martian Liquid Brines," was co-authored by Vincent Chevrier, an associate research professor at the University of Arkansas's Center for Space and Planetary Sciences, and Rachel Slank, a postdoctoral fellow at The Lunar and Planetary Institute in Houston, Texas. The goal of the paper is to educate the public on the current state of knowledge regarding the existence of liquid water on Mars.
'Lot of Confusion, Lot of Misunderstanding'
Chevrier, who has spent the last 20 years studying Mars for signs of liquid water, said, "I wanted to write this paper for a very long time". Explaining his reason to write this paper, he added, "I think there is a lot of confusion, a lot of misunderstanding, and a lot of erroneous interpretations of what the research papers are saying about the state of liquid water on Mars." Chevrier is as invested as anyone in there being liquid water on Mars, but he thinks the evidence just isn't there yet.
The researchers revealed that a closer sight at the RSLs indicated their behaviour is consistent with sand and dust flows without any need of water to create them. The data available from Martian orbiters also cannot confirm that liquid water plays any role in RSL development.Bottom of Form
Other researchers feel that the existing brines, which are solutions with a high concentration of salts, such as Earth's oceans, may hold the key to finding liquid water on Mars.
According to study, brines can freeze at much lower temperatures, and there is an abundance of salts on Mars. Of those salts, perchlorates would seem to be the most promising, since they have extremely low eutectic temperatures (which is when the melting point of a mixture is lower than any single ingredient).
For instance, a calcium perchlorate brine solidifies at -75 degrees Celsius, while Mars has an average surface temperature of -50 C at the equator, theoretically suggesting there could be a zone where calcium perchlorate brine could stay liquid, particularly in the subsurface.
After examining all of the arguments for and against brines potentially forming stable liquids, Chevrier and Slank concluded that the various limiting factors, including the relatively low amounts of the most promising salts, water vapor pressure and ice location "strongly limit the abundances of brines on the surface or shallow subsurface." Even if brines did form, the researchers think that they would "remain highly un-habitable by terrestrial standards."
Major Objective of Mars Exploration
In the last section of the latest study, the researchers stated, "Despite these drawbacks and limitations, there is always the possibility that Martian life adapted to those brines and some terrestrial organisms could survive in them, which is a consideration for planetary protection because life on Mars might exist today in that case. Hence, detecting brines in situ remains a major objective of the exploration of the red planet."
In addition, the authors suggested that the next step would require improved instruments to detect small amounts of brines, doing a better job of identifying the best places to look for them, and being able to conduct more laboratory measurements under Martian conditions.
"Despite our best efforts to prove otherwise," Chevrier concluded, "Mars still remains a cold, dry and utterly unhabitable desert."
