Water on Mars

There was water on Mars! More than 3 billion years ago, the Red Planet had an ocean, lakes and rivers. During periods known as the Noachian (4.1-3.7 billion years ago) and the Hesperian (3.7-2.9 billion years ago), Mars may have been suitable for life similar to our own. Later, however, it lost most of its atmosphere, and with it the ability to hold liquid water on the surface. While much of it must have escaped into space, scientists assume that large deposits may still be waiting stored beneath the globe’s surface.

Mars’ former surface water may have been incorporated into minerals, buried as ice or, what would be best for us, stored somewhere deep as liquid in aquifers. By studying the propagation velocity of seismic waves within a 50-km radius around the InSight lander on Elysium Planitia, a group of scientists from the Scripps Institution of Oceanography, the University of California, San Diego, and the Department of Earth and Planetary Sciences at the University of California, Berkeley, developed a model of water saturation in rocks at depths of ∼11.5-20 km using rock physics algorithms and Bayesian inference with Markov chain Monte Carlo sampling.

Scientists have concluded that from the data collected, the central crust of Mars, composed of fractured magma rocks, is saturated with liquid water. This has implications not so much for future manned missions to Mars (the liquid deposits are too deep for that), but for future attempts to find life on the Red Planet.

Water on Mars – Red Planet

“We are alive, so we would like to preach the idea of life everywhere. […] I remember staring mesmerized at the first image of the horizon of Mars. This is not an alien world,” I thought. I knew similar places in Colorado, Arizona, Nevada…” – Carl Sagan, 1979, Cosmos

Mars is the closest planet to Earth. In addition, it could in the past and still can host life similar to ours, although on the surface, away from the ice caps, it is drier there today than in the driest place on our globe, the Atacama Desert in Chile. The search for life on Mars was dedicated to the experiments of the first American probes Viking 1 and Viking 2 sent to the Red Planet in 1976. Their results – interpreted in a variety of ways – have become a staple of discussions among astrobiologists that continue to this day.

Both probes have confirmed the existence of life, operating in different locations and producing repeatable results. NASA stated that the results of the experiments Labeled Release were disturbed by specific soil conditions, but similar experiments were never conducted again. Their designer – Gilbert Victor Levin – claimed until his death in 2021 that he had discovered life on Mars and history would do him justice.

Is it any wonder that we are looking for life on the Red Planet? Carl Sagan, one of the pioneers of astrobiology, who remained skeptical about the results of the experiments performed by the Viking probes, pointed out in his book Cosmos that terrestrial life appeared almost immediately after the formation of our planet. Therefore, it can be thought that it is an inevitable process under certain conditions. The possibility of the existence of living organisms in the deep layers of Mars rocks has been postulated by geomicrobiologists working with astrobiologists, such as. Tullis C. Onstott. He uses the analogy of the extremophilic bacteria Desulforudis audaxviator discovered in the depths of the Earth, which live thanks to radioactive decay and die on contact with oxygen, and the nematode Halicephalobus mephisto, which feeds on such bacteria, which he discovered, together with Gaetan Borgonie, in gold mines in South Africa.

From a completely different perspective, we can assess the chances of life on Mars in the past, since it may not have been a red planet, but a blue planet, just like Earth.

Water on Mars has historically been found in large quantities

Mars has never been as blue as Earth. However, scientists have no doubt that water must have been present there in large quantities in the past. An analysis of images of its surface, those from Viking, those collected between 1999 and 2006 by the Mars Global Surveyor probe or by the Mars Express orbiter since 2003, suffice to reach this conclusion. They show gigantic structures carved by water billions of years ago – networks of valleys resembling the outflow channels of rivers in the regions of Cydonia Mensa, Deuteronilus, Acheron Fossae or southern Elysium and the shores of the great ocean in the north of the planet.

Located in the highlands, the Noachian impact craters, dating back to the Great Bombardment that hit the inner planets of the solar system hard some 3.9 billion years ago, are quite heavily eroded by precipitation. Many of them were filled in the past with volcanic lakes that could hold hundreds of thousands of cubic kilometers of water, such as those at the bottom of the Hellas and Argyre impact basins (2,300 and 1,800 kilometers in diameter and 7.15 and 5.2 kilometers deep, respectively). After the craters eroded, water flowed out of them, carving river valleys. Traces of glacial activity can also be seen at their edges, as at the foot of Olympus Mons or on the western slopes of the Tharsis volcanoes. You can see places where the ice has evaporated, leaving behind piles of worn stones.

The second piece of evidence is the hydrated minerals detected on the surface of Mars, such as saponite and montmorillonite, whose formation requires the presence of liquid water. It is estimated that at its peak, during the first billion years of the Red Planet’s existence, a third of its surface may have been covered by ice and liquid water. Geological rationale suggests that this would have yielded an amount equivalent to a global water layer (GEL) 0.5 km thick. Earth’s surface water, by comparison, has an average thickness of about 2 km. If Mars were to have the same ratio of water to planetary mass, it would be a layer about 1 km thick. The question is what happened to this water. All of it escaped into space or does any part of it remain hidden under the surface of the Red Planet?

Times of global cataclysms

When Mars had a dense atmosphere, sizable amounts of water were able to seep into its crust and form a planetary groundwater system. When Mars cooled after the Great Bombardment at the end of the Noachian (3.7 billion years ago), its surface froze. A layer of ice then formed as a barrier between the atmosphere and the ground, isolating groundwater from the planet’s surface. Mars lost most of its atmosphere at that time.

As a result of the planet’s subsequent volcanic activity, some of the water trapped in the aquifer escaped to the surface. This occurred during the Hesperian period (3.7-2.9 billion years ago), causing widespread and powerful floods. Periodically, permanent reservoirs of water may have appeared in the hesperian, which disappeared over time. The water from them then went into the thinning atmosphere, from where, unable to return beneath the surface, capped by a layer of perpetually frozen cryolithosphere, it escaped into space. This process continues to this day.

The water cycle and seasons on Mars

Observations have proven that a water cycle still exists on Mars. It involves the exchange of water with the regolith and polar caps and is closely linked to the planet’s seasonal weather cycles. Most water vapor is seen in summer over the poles. It comes from the process of sublimation of the ice caps, in which, in addition to frozen carbon dioxide, water ice is still present. In winter, the temperature on Mars drops so that carbon dioxide, the main atmospheric gas, condenses to form frost or ice. It then forms seasonal polar caps reaching as high as 40° latitude.

Water vapor at high latitudes also freezes at this time, and then is released in the spring when the planet’s surface warms up again. The sublimating atmosphere gets up to 30 percent thicker in summer. denser (the density of Mars’ atmosphere is barely 4-8.7 mbar, with an average of 6.36 mbar and the average density of Earth’s atmosphere – 1,000 mbar). The Mars Odyssey orbiter, which since 2002. has already circled the Red Planet nearly 100,000. times, has provided numerous observations of the rapid response of the ice just below the Martian surface to climate change.

A factor in the transformation of Mars’ atmosphere is the steady escape of gas into space. High up in the exosphere, a corona of hydrogen atoms can be seen traveling on ballistic trajectories without collision. Some are flashing quite fast to fly off into space. Thus, in atmospheric water vapor, the ratio of deuterium to hydrogen increases steadily (deuterium is the heavier isotope of the element, so it is much harder for it to fly off into space). Based on the hydrogen isotope ratio, Bruce Jakosky inferred a water loss of 80-99 percent. relative to the baseline value.

This initial isotope ratio is known from samples of Martian minerals collected by the Curiosity rover, but also from Martian-origin meteorites, such as ALH84001, famous for its presumed traces of life (most Martian rocks on Earth come from the Tharsis and Elysium regions). Victor Baker stipulated, however, that the volume of water resources trapped in the deeper parts of the planet’s mantle cannot be estimated on this basis due to their early and permanent severance by the cryolithosphere, which is a few kilometers thick at the equator to up to a dozen kilometers thick at the poles.

Water transformed into stone

Some of Mars’ water may have been preserved in the form of hydrated minerals. In 2021. Eva Linghan Scheller and Bethany List Ehlmann, with a team from Caltech, found that 30 to as much as 99 percent of the of Mars’ former water resources may have been tied up by hydration of the Martian crust. What interests us most, however, in terms of future manned expeditions or permanent colonization of the neighboring planet, is water that can be used in a more accessible way. Traces of a massive subsurface water eruption, combined with volcanic lava flows on the Cerberus Plain, are only about 10 million years old! July 2018. ESA’s Mars Express orbiter has discovered, using radar, an underground reservoir of liquid water near the South Pole. She is still out there somewhere….