| Wed February 5th 2020 16:00 – 17:00 ZH286 | Seminar | Atmosphere-surface exchange of water on present-day Mars Norbert Schörghofer |
Details:The exploration of planet Mars over the last two decades (by 6 orbiters, 3 rovers, and 2 landers) has lead to a host of discoveries that motivate theoretical investigations into the physical processes that govern the climate system and ice reservoirs on Mars. The Martian atmosphere consists primarily of carbon dioxide and the surface pressure is close to the triple point of water (6 mbar). Hence, near the melting point, humid air is significantly lighter than dry air, and its buoyancy drives free convection. Evaporative cooling prevents ice from reaching the melting point, which represents a major physical barrier to the formation of liquid water on Mars. Sudden transitions from seasonal shadow to sunlit conditions occur in favorable geometries (at the pole-ward end of boulders), and may be a pathway to the formation of transient liquid water on Mars. Another key process is thermally driven diffusion of water vapor within the porous subsurface. Daily and seasonal water cycles can pump water vapor into the ground. The amplitude of periodic temperature oscillations quickly decays with depth, and the nonlinear dependence of the saturation vapor pressure on temperature can result in net downward transport of vapor. This process deposits ice in pore spaces and produces ice filaments and bubbles, without involvement of the liquid phase. This pumping effect is rare on Earth, but on Mars it is responsible for the creation of vast near-surface ice reservoirs. | ||
