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Abstract

Since the formation of the Solar System some 4.55 billion years ago, the Sun has provided the necessary conditions to allow life on Earth to begin forming, evolve and thrive. As a main sequence star, the Sun is exhausting its reserves of hydrogen at its core over time as it is fused into helium. Once this process – known as solar reddening – has been completed and helium fusion begins in the core, the Sun will become a red giant. This evolution will lead to fluctuations in the solar properties such as mass, luminosity, radius and surface temperature. While solar-reddening will likely be catastrophic for the inner-most planets, it could present an opportunity for Saturn’s moon Titan and the dwarf planet Pluto as the Sun’s luminosity increases. Titan and Pluto are of significant interest due to their photochemically-active atmospheres, both of which are mostly made up of nitrogen with traces of methane. We will present a model for simulating planetary atmospheres in orbit around reddening stars, with case-studies investigating how Titan and Pluto’s atmospheric and surface conditions will change between the solar ages of 4.55 and 12.15 Gyr. Our model builds upon the TitanIC (Titan Irradiative Chemistry) model, first created by Borg (2015). We will also present how the model can also be used to simulate exoplanet atmospheres of known initial compositions for a host star with a given set of solar parameters. Borg, J., 2015. Projecting the Evolution of Titan’s Atmosphere under a Reddening Sun. University of Malta.