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Mars’ atmosphere, volatiles, and climate as the Sun heats up over the next 5 billion years

Presentation #318.09 in the session Mars’s Story as Told and Influenced by Dust and Water (Oral Presentation)

Published onOct 23, 2023
Mars’ atmosphere, volatiles, and climate as the Sun heats up over the next 5 billion years

The Martian atmosphere and climate system will respond as the solar luminosity continues to increase over the next 5 billion years. The Mars surface will heat up to above the melting temperature of water ice, even without greenhouse warming. Water ice currently in the polar caps and ground ice will melt, potentially repopulating crater lakes or a very small ocean, with the abundance possibly enhanced due to diffusion outward of water currently locked in the crust. The CO2 currently adsorbed in the regolith and locked up in the polar ice cap will diffuse into the atmosphere, providing up to 50 mbar total; this would increase the temperature further (albeit only slightly) via greenhouse warming. There are two end-member scenarios of what the climate could look like: (i) Surface water could drive an atmospheric water cycle somewhat analogous to present-day Earth’s; this would create a global clement climate conducive to the existence of widespread life. While Earth’s climate could have a transition to be more Venus-like as the Sun heats up, Mars could become more Earth-like. (ii) The widespread presence of liquid water could cause H2O to hydrate surface/subsurface minerals (or allow H released from water to escape to space) and CO2 to form carbonates, leaving Mars to continue with a dry, lifeless environment. It’s not possible to determine which of these end-members (or where in between) actually will occur – the water cycle under these conditions is too different from any well-constrained model to allow us to predict how robust it would be or how effective in producing the sustained physical and chemical weathering required to remove CO2 and H2O from the atmosphere. This changing climate reminds us that exoplanet evolution and habitability can be driven by endogenous processes associated with a terrestrial planet as well as by the ability of EUV and a stellar wind from the host star to strip away atmosphere.

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