Water on Mars – where is it?

In June 2008, the Phoenix lander excavated water ice beneath just a few centimeters of Martian regolith on Vastitas Borealis (the bottom of Mars’ primordial ocean), and identified water in ground samples. The exposed ice sublimated over several days. Mars Recconesaince Orbiter discovered glaciers covered by a layer of dust closer to the Red Planet’s equator. They may be 80-170 meters thick and the result of long-term snowfall. As the tilt of Mars’ axis changes over time, the ice travels in longer cycles from the polar caps to mid-latitudes at higher tilt (>35°) and retreats from there, returning to the poles at lower tilt (currently 25.19°).

However, overlapping craters in the Arcadia and Utopia Planitiae region, located at mid-latitudes, showed that ice has been present there for tens of millions of years. This negated previously prevailing Mars climate models. Colin Dundas and his team pointed to numerous clefts of erosional origin, revealing ice at ±55° latitudes. February 2022. Mars Recconesaince Orbiter filmed a new impact crater with a diameter of 150 meters, which had formed barely two months earlier. This crater, located near 35°N, exposed the farthest equatorward deposits of water ice. In August 2023. The orbiter picked up traces of the movement of rock material through glaciers away from the poles.

Thus, it is assumed that in addition to the ice caps, 1/3 of the planet has subsurface water ice deposits. The water we identify on the surface of Mars yields some 20-30 m of global equivalent layer (GEL). While the area around the InSight lander is representative, the latest seismic survey of Mars’ inner mantle by Vashan Wright’s team adds the equivalent of 1-2 km of global equivalent layer (GEL) water, trapped deep in the porous rocks of the mantle. Mars therefore did not have to lose all its water to space.

This is a gigantic amount, but the depth of this layer of rock ~11.5 to 20 km is too much for us to use this water for manned missions or even attempts to colonize the planet. On the other hand, however, it’s far more than is needed to fill the former Martian ocean, and could have huge implications for the survival of former Martian life at that depth….

There used to be life there…

In 1984. In the Allan Hills in Antarctica, the ALH84001 meteorite from Mars has been discovered. The stone was formed four and a half billion years ago, when the Red Planet was still young. Some 17 million years ago it was ejected from Mars due to an impact of another celestial body. About 13,000 years ago, the stone fell to Earth. An atmosphere from Mars was found in it, and in 1996 astrobiologist David S. McKay spotted… markers of life! Polycyclic aromatic hydrocarbons, present only in the interior of the meteor, not on its surface, could not be the result of terrestrial contamination.

Mineral structures similar to fossils of terrestrial organisms, such as chains of magnetite crystals, are used by some terrestrial bacteria to orient themselves in magnetic fields. However, the discoveries have stirred up quite a bit of controversy. The signatures could have been created by non-biological processes, including the passage of a meteor through Earth’s atmosphere.

On Mars, as on Earth, there are still processes we don’t understand. In June 2013, NASA’s Curiosity rover, followed shortly thereafter by ESA’s Mars Express orbiter, detected an unexpected peak of methane, a gas previously unrecorded in Mars’ atmosphere, over Gale Crater. Methane may or may not be the product of biological processes, although most of this gas present on Earth is the result of life on Earth.

In July 2024, the Mars rover Preservance found a arrowhead-shaped rock at the bottom of Jezero Crater and a former river delta. Covered with bright veins of calcium sulfate, the rock – evidence that it once resided in water – was named Cheyava Falls after the highest waterfall in the Grand Canyon of Colorado. Thanks to the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instrument, chemical signatures of organic compounds were detected in it. The naked eye can see structures that may be traces of microbial life from billions of years ago, when water was still flowing through Neretva Vallis.

These are distinctive bright spots of millimeter size, surrounded by dark borders, which may contain iron and phosphates. On Earth, such spots are formed when organic molecules react with hematite or oxidized iron – these reactions are the fuel of Earth’s bacteria. Unfortunately, the rover does not have the necessary laboratory to thoroughly study the rock, while the program to transport samples from Mars to Earth, NASA’s and ESA’s joint Mars Sample Return, may lose funding….

What’s next for Mars?

Will there ever be liquid water reservoirs on the surface of Mars again? Terraforming the Red Planet is not the subject of this text, but such ideas have been maturing for a long time, being born first in the minds of science fiction writers, such as Kim Stanley Robinson, author of the Red / Green / Blue Mars trilogy. Undoubtedly, the issue is not easy. Nearly ten times smaller than Earth, Mars is devoid of plate tectonics. It lacks a magnetic field that could protect the surface from lethal radiation from solar winds, which causes a high concentration of highly disinfecting perhydrol on it. Gravity is too low to sustain the atmosphere for long. And yet.

In 1971, Carl Sagan proposed covering Mars’ ice caps with something dark in order to vaporize them and thicken the atmosphere. The agreed-upon direction was to raise the planet’s temperature to create conditions for life based on photosynthesis, and only then to increase the oxygen level in the atmosphere. In subsequent decades, orbiting mirrors or the use of powerful greenhouse gases, such as chlorofluorocarbons, were proposed to warm the planet. In 2019. Robin Wodworth and Laura Kerber and their team proposed locally spreading silica aerogel covers 2-3 cm thick over the ice. It would simultaneously transmit enough light for photosynthesis and block ultraviolet radiation, and raise the temperature underneath above the melting point of water. The purpose of such a treatment would be to create local conditions for the survival of photosynthesis-based life….

In August 2024, a group of scientists on Edwin Kite’s team, building on a concept by Nobel laureate John Hasbrouck van Vleck (among others, co-founder of the Los Alamos Nuclear Weapons Laboratory and a member of the Manhattan Project), proposed heating Mars using an aerosol of nanowires made of iron or aluminum – elements available in Martian regolith (carbon is also being considered). According to their calculations, electrically conductive rods about nine micrometers long could warm Mars more than five thousand times more efficiently than the most powerful greenhouse gases, and these would, after all, require elements rarely found on the Red Planet’s surface.

The nanowires would scatter sunlight in one direction and block infrared reflected by the planet’s surface in the other. Like Martian dust, which glides up to a height of 60 km, they would be carried high into Mars’ atmosphere. Unlike dust, which cools the planet, they would filter infrared radiation in only one direction. Climate models suggest that a steady release of particles at 1.5 million tons per year – to a density of 10 million tons in the atmosphere, would warm Mars by more than 30°C. As temperatures rise, carbon dioxide and water vapor – a highly effective greenhouse gas – would go to work, sublimating ever faster from Mars’ ice caps. The atmosphere would begin to thicken, the ice would melt, and water would flow again over the Red Planet’s surface….

The dilemma of whether, if there is life there, we are allowed to affect it, and most likely destroy it with life brought from Earth, whether inadvertently or for terraforming purposes, I leave for another occasion.

Photo. main: NASA