Carbonate formation and fluctuating habitability on Mars

Area of Science:

• Planetary Science
• Astrobiology
• Geochemistry

Background:

• The cause of Mars's lost surface habitability remains unclear, with evidence pointing to a 'missing sink' for carbonate.
• Sedimentary rocks, like those at Gale Crater, indicate past intermittent surface and subsurface liquid water.
• This water's patchy and late-stage presence suggests a mechanism for sequestration, possibly carbonate formation.

Purpose of the Study:

• To investigate the cause of Mars's loss of surface habitability.
• To explain the existence of intermittent liquid water on Mars through a self-regulating mechanism.
• To model the interplay between solar luminosity, water, and carbonate formation.

Main Methods:

• Development of a model incorporating solar luminosity, liquid water stability, and carbonate formation.
• Simulation of negative feedback loops between these factors.
• Analysis of chaotic orbital forcing's effect on wet-dry cycles.
• Modeling snowmelt and groundwater as potential water sources.

Main Results:

• A negative feedback mechanism was identified where increasing solar luminosity initially promoted liquid water, which then formed carbonate.
• Carbonate formation reduced atmospheric carbon dioxide, limiting further liquid water and creating intermittent oases.
• Chaotic orbital forcing influenced wet-dry cycles, with the feedback restricting water to specific areas.
• The model suggests Mars self-regulated as a desert planet, with Gale Crater recording key water stability episodes.

Conclusions:

• The proposed negative feedback loop offers a plausible explanation for Mars's intermittent habitability and eventual desertification.
• This mechanism explains how Mars could have sustained liquid water in localized oases despite decreasing solar luminosity.
• Further research is needed to confirm the representativeness of Gale Crater's carbonate content for the entire planet.