Pham, L.B.S.

PhD thesis supervised by Dehant, V. (UCLouvain)

Abstract: Geomorphological and geological evidences show that liquid water has flowed on the martian surface, particularly at the end of the Noachian period (3.8−3.9 Gyr ago). However, surface pressure and temperature during this period are not well defined and there is up to now no consensus on the climate evolution of Early Mars. We investigate atmospheric mass and climate evolution of Mars. The effects of impacts on the atmospheric mass budget of the planet are calculated with the use of a semi-analytic model developed during this study. We also consider the contribution of other factors of atmospheric mass evolution, such as volcanic outgassing and non-thermal escape processes. To study the climate, we construct a one-dimensional energy balance model, in which meridional heat transport and greenhouse warming are included. We show that impacts alone can hardly remove significant amount of atmospheric mass between the end of the Noachian and present. The atmospheric loss by the other mechanisms is also small, except maybe the sequestration of carbon dioxide in carbonate reservoirs. Based on the estimated atmospheric pressures and assumed greenhouse warming, we show that saline solutions, possible for temperatures higher than 245 K, can only flow sporadically on Early Mars, at high latitudes and during high obliquity periods. Other sources of transient warming are then needed to allow the presence of liquid water.

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