Mars used to be wet. This is the overwhelming conclusion of the geological research of Mars, based on data recorded by various probes and landers. It took us much longer to confirm the planet’s previous state than the current one – we had strong evidence suggesting that dry conditions on Mars date back to 1894, with additional confirmatory evidence gathered over the next 30 years. The current model for the transformation of Mars from a wet planet to a dry one is based on sublimation and the long-term damage our sun has done to the Martian atmosphere after the planet’s global magnetic field closed. But what if that’s not true?
This is the argument presented in a new article, which claims that the waters of Mars could technically go nowhere.
The evidence we get from robbers like Persistence, Curiosity, Opportunity, en spirit, together with planetary observations of orbiting satellites, jointly suggest that Mars enjoyed a relatively warm, wet era from 4.1B to 3.7B years ago. Some evidence for the so-called Late Heavy Bombardment comes from the large number of craters on Mars and the Moon that were apparently created during this period. Craters formed during this era eroded ridges similar to what we would expect from flowing water. Craters created later, during the Hesperian period (~ 3.7 – 3 billion years ago), are much less weathered.
Several factors enabled Mars to maintain an atmosphere during this period. The enormous series of volcanoes known as the Tharsis outcrop was actively under construction. The Tharsis outcrop is a volcanic province about the size of North America. The total amount of CO2 released during the Tharsis eruptions is considered sufficient to form a 1.5-bar atmosphere on Mars, with a world sea up to 120m provided by this source alone. Tharsis is large enough that its formation may have caused Mars to tilt to one side and change the location of the poles in the process. Massive effects could potentially produce extra water of their own, and early Mars might have had enough surface water to cover the surface of the planet up to 1500 meters deep. These uncertainties are the reason why the Global Equivalent Layer (GEL) estimates are so variable.
One reason why scientists think that Mars’ water has evaporated is that the atmosphere of Mars and water samples were taken Curiosity both show an excess of deuterium in relation to hydrogen compared to what we would find on earth. This suggests that lighter ordinary hydrogen was preferably lost in space, while the heavier deuterium isotope remained.
The problem with the sublimation / atmospheric loss model is that current loss rates are not high enough to account for the magnitude of Mars’ transformation over the past few years. It is known that the solar wind played a long-term role, but how can we account for the rest? One theory is that mass loss rates used to be much higher. These researchers suggest that much of Mars’ water remained just there and rather became trapped in surface minerals.
Over time, water flowed downward and froze on the surface, while other water sublimated away into space. Image by ScienceMag
We are not talking about the idea of a layer of liquid being stored below the surface. The research report discusses ‘crust hydration through irreversible chemical weathering, in which water and / or hydroxyl are taken up in minerals.’ The water is not available for other purposes on Mars; it is directly embedded in the crystalline structure of the minerals.
Herein lies a critical difference between Mars and Earth. Mars has a tectonic system with a stationary lid, which means that there is no plate tectonics and that there is no system for rock recovery – or, critically, water. On Earth, plate tectonics carry water deep into the mantle, while volcanic openings in the middle of the ocean bring it back to the oceans. This is called the deep water cycle.
As long as Mars’ volcanoes continued to erupt, it maintained a deep water cycle of its own. Once the process began to slow down, water began a one-way sequestration in the earth’s crust. Influence and faded eruptions would maintain a colder climate with at least volatile liquid water for a long period of time – Mars has dried up over several hundred million years – but the end of volcanism may have been between a third and almost all of Mars’ water made possible. to flow into the soil and form hydraulic minerals. In extension, this means that Mars’ water reserves are much higher than previously thought, although locked up in a mold, we will not find them so useful.
We may not know if the report is accurate until and when humans are capable of conducting large-scale geological investigations of subterranean rock, but it is an alternative model for how Mars lost its atmosphere that explains the current conditions well. This would further imply that features of the earth, such as plate tectonics, could be crucial to the long-term conservation of a biosphere that could support intelligent life.
Image by Ittiz, CC BY-SA 3.0
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