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Communication Dans Un Congrès Année : 2018

Isotopic Fractionation of O and C in the Photochemical Escape of Early Mars

Jean-Yves Chaufray
François Leblanc

Résumé

The isotopic ratios of 13C/12C and 18O/16O on Mars record important information on the atmosphere evolution of the planet. In this work, a 3-D Monte Carlo Model is used to investigate the isotope fractionation effects of C and O in photodissociation (PD) and dissociative recombination (DR) escape processes. Theoretical ionosphere and thermosphere structures corresponding to solar activity levels 2.5, 3.8, and 4.1 Gyrs ago are considered. The contribution of secondary energetic particles to the isotopic fractionation effect is also considered in this work. Our work shows that the Rayleigh fractionation factors in these escape processes depend on solar XUV levels. Using the calculated fractionation factors, we trace the evolution of Mars atmosphere and conclude that 180 mbar CO2 and 360 mbar H2O ( 10m GEL of water) could have been lost to space due to these studied escape processes since 4.5 Gyrs ago. The atmospheric escape and isotope fractionation effects of C and O are more efficiency compare to previous work.
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insu-04407328 , version 1 (20-01-2024)

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J. Zhao, E. Chassefiere, F. Tian, Jean-Yves Chaufray, François Leblanc. Isotopic Fractionation of O and C in the Photochemical Escape of Early Mars. American Geophysical Union, Fall Meeting 2018, Dec 2018, Washington, United States. ⟨insu-04407328⟩
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