When we found what appeared to be flowing liquid water In 2015, scientists around the world were eager to test it. There was only one problem, and it was one problem: the United Nations Outer Space Treaty 1967 requires that space exploration be conducted in a manner to avoid contamination.
Since we have no way to completely sterilize our equipment against Earth's microbes, this means that there is no contact with water.
However, according to new research, we shouldn't have worried, although there may be saline liquid water on Mars, otherwise surface conditions are really inhospitable for terrestrial life. .
"Life on Earth, even extreme life, has certain environmental limits that it can endure." explained the planetary scientist Edgard G. Rivera-ValentÃn the University Space Research Association (USRA) and the Lunar and Planetary Institute (LPI).
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"We have studied the distribution and chemistry of stable liquids on Mars to understand whether these environments would be suitable for at least extreme life on Earth."
In trying to understand how life could exist elsewhere, we often observe Extremophiles, organisms that live in some of the most extreme environments on Earth. These included the arid desert of Atacama in Chile, Dallol's acid and salt geothermal area in Ethiopia, and even in space close to Earth on board the ISS.
But if these environments have something in common with Mars, they are clearly do not March. Liquid water seems to be a prerequisite for life, but on Mars, liquid fresh water cannot stay on the surface. It is so dry and cold there that the water Freeze
or evaporate
Of course, water does not need to be fresh to maintain life. The salty oceans of Earth are full of them. And we know that the sodium, magnesium and calcium salts are abundant on Mars; If these salts were mixed with water to create a solution rich in salt called brine, this would lower the freezing point and reduce the rate of evaporation of the liquid, which could allow it to stay on the surface .
And if there was enough moisture in the Martian atmosphere, some of the salts could undergo a process called deliquescence, so they absorb moisture to form a liquid solution.
But questions remain: can this liquid brine form and remain on the Martian surface long enough for life on Earth to prosper?
"Our team examined specific regions of Mars, areas where liquid water temperatures and limits of accessibility could potentially allow replication of known terrestrial organisms, in order to understand if ; they could be habitable. " said the planetologist Alejandro Soto
from the Southwest Research Institute.
"We are using Martian climate information from atmospheric models and spatial measurements. We have developed a model to predict where, when and for how long brines are stable on the surface and in the subsoil of the surface of Mars. "
Based on years of experimental data on chemical reactions in laboratory-simulated Mars conditions, as well as meteorological data, the team gathered an image of when and where liquid brines could be present at the surface of Mars, and a few centimeters below.
They discovered that liquid brines can persist for up to six hours from the equator at high latitudes, more than 40% of the Martian surface. And that could only happen seasonally, for about 2% of the year.
It may not sound like much, but it is a wider range than scientists previously thought. But that still doesn't mean that life on Earth could survive there.
"The highest temperature a stable brine will experience on Mars is -48 degrees Celsius (-55 degrees Fahrenheit)" Rivera-Valentin said. "It's well below the lowest temperature we know life can tolerate."
This means, concluded the team, that Martian brines do not meet the requirements of the special region established by the Space Research Committee (COSPAR) of the International Council for Science, and therefore should not be an obstacle to a manned Mars exploration mission.
It is also important to note that these results have no relation to the native life of Mars, if they exist or have existed throughout the history of the planet, they are entirely based on our understanding of earthly life. And that could also be a limitation.
"We have shown that, on a planetary scale, the Martian surface and subsoil would not be suitable for terrestrial organisms because liquids can only form on rare occasions, and even then, they form under difficult conditions. " Rivera-Valentin said.
However, there could be an unexplored life on Earth that would be happy under these conditions. "
The research was published in Nature astronomy.