Water Supersaturation for Early Mars

Abstract

Evidence of past liquid water flowing on the surface of Mars has been identified since the first orbital mission to the planet. However, reconstructing the climate that would allow liquid water at the surface is still an intense area of research. Previous studies showed that an atmosphere composed only of CO2 and H2O could not sustain surface temperatures above the freezing point of water. Different solutions have been studied, ranging from events like impacts on different atmospheric compositions, or even radiative feedback of water clouds that would create a dramatic greenhouse effect. In this context, we propose to study whether the supersaturation of water could warm the planet. Strong supersaturation is observed in the present‐day Martian atmosphere. On early Mars, supersaturation could enhance the greenhouse effect through strong absorption of the IR flux by water vapor or by modifying water clouds. While 1D modeling suggests a significant impact, our 3D model shows that warming the climate of early Mars requires a high supersaturation ratio, especially in the lower layers of the atmosphere. This configuration seems highly unrealistic since the level of supersaturation is higher than what would be expected in a dense atmosphere.