The Center for Atmospheric Sciences | » Deciphering the Genesis of Modern Earth and Venus through the Carbon Cycle: How Surface Dynamics Influence Mantle Properties

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  • Deciphering the Genesis of Modern Earth and Venus through the Carbon Cycle: How Surface Dynamics Influence Mantle Properties

    Earth and Venus are planets of similar mass and structure that likely started off quite similarly but somehow over time developed very different atmospheres.  Venus’ high surface temperature is due to a runaway greenhouse effect, chiefly caused by a carbon cycle that has transferred mostly the planet’s entire carbon reservoir into the atmosphere. It is currently unknown why the paths of the two planets diverged so greatly, but one method by which some insight on this matter may be gleaned would be to look at how carbon is cycled globally through a coupling of the mantle and atmosphere.

    In this study, we look at a simplified planetary model, consisting of two regions: atmosphere and mantle. The two regions are connected by two fluxes: volcanism which moves carbon dioxide from the mantle to the atmosphere and weathering which returns carbon dioxide to the mantle.  Each region starts with a certain amount of carbon dioxide. The surface temperature is calculated using a parametrization of the results of radiative-convective atmospheric models.  Carbon dioxide is allowed to flow through the system until a steady state is achieved. The effects of solar intensity and atmospheric water-vapor saturation on the CO2-surface-temperature relationship are studied to determine the possible causes for differences in the evolutionary paths of Earth and Venus.

    The objective of this research experiment is to perform a theoretical comparative planetology experiment examining the coupled dynamics of atmospheric temperature and mantle dynamics through a simplified long-term carbon/water cycle. The results of this modeling experiment could be applied to a variety of aerospace areas. With a general understanding of the coupling of the mantle dynamics to the atmosphere, one could gain some insight into how the Earth’s dynamo has evolved over time and what surface conditions might affect the magnetosphere. The results of this research could greatly elucidate the geological and atmospheric evolution of Venus. This research could also be applied to extrasolar planets. Of the few things we will be able to detect about these distant planets, the planet’s size, composition of the atmosphere, and magnetic field strength might be able to tell us something about the tectonic evolution of the planet and whether it has habitable conditions. The results would also give us some indication of the ratio of Earth-like planets to Venus-like planets that we see, as of right now we don’t have any way of telling how many planets of Earth-like size will suffer the fate of each of these two twin planets, and also what characteristics we should seek to travel to the right type of planet.