The second model sought to determine the physical and chemical properties of the porous Martian crust – namely, temperature, chemical composition and the presence of liquid water. They are determined partly by surface conditions (i.e., surface temperature and atmospheric composition) and partly by the planet’s internal properties (i.e., internal thermal gradient and crust porosity).
These two prototypes enabled us to simulate the surface and subsurface environments of the young planet Mars. However, many uncertainties remain regarding the main characteristics of this environment (eg, the level of volcanic activity at that time and the crust’s thermal gradient). To remedy this problem, we used our model to explore a plethora of potential properties, resulting in a range of scenarios regarding how Mars might have appeared about four billion years ago.
The third and final model concerns the biology of the hypothetical methanogen microorganisms of Mars, based on the theory that they were similar to methanogens on Earth, at least in terms of energy needs. Using this model, we can assess the habitability on Earth of our microbes compared to the environmental conditions underground on Mars, according to each environmental scenario generated by the previous two models.
When the particular conditions were considered habitable, the third model assessed how these microorganisms survived beneath the Martian surface—and along with models of the crust and the surface—how this underground microbial biosphere affected the chemical makeup of the crust, as well as the atmosphere and climate. By combining the microscopic scale of the biology of methane-generating microbes with the global scale of the Martian climate, together these three models have helped simulate the behavior of the Martian ecosystem.
It is very likely that there is habitability underground within the crust of Mars
A number of geological clues point to the flow of liquid water on Mars four billion years ago, which would have formed rivers, lakes, and possibly even oceans. So the climate of Mars was much milder than it is today. In explaining how such a climate occurred, our surface model posits that Mars had a dense atmosphere (about the same density as our planet today) that was particularly rich in CO2 and H2, even more so than planet Earth. in time.
The CO2-rich atmosphere context may have provided the H2 atmosphere with remarkably strong greenhouse gas properties. H2 would have been stronger than CH4 under the same conditions. In other words, if 1% of Mars’ atmosphere was H2, the climate would be warming more than if 1% was CH4.
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