Abstract: RSSD seminar on climate research of Mars
At present, Mars is a dry and cold planet/ Its climate system is nonetheless complex and highly variable, mostly because of the coupling between atmospheric circulation, including the dust cycle (lifting of dust storms), and the CO2 cycle (condensation and sublimation of the CO2 atmosphere onto seasonal polar caps). A peculiar water cycle does occur on Mars, with water vapour transported by the atmosphere between the poorly known subsurface reservoirs and the polar caps, allowing the formation of clouds, hazes and frost. However, the amount of water involved remains very small. Consequently, surface ice is unstable outside the polar regions. Furthermore, the atmosphere is so cold and so dry that the presence of liquid water, never detected, is unlikely anywhere on the surface.
Things may have been different in the past. On the one hand, the surface of Mars contains by multiple geological signatures that suggest that various kind of glaciers and ice sheets formed not that long ago at low and mid-latitudes. On the other hand, liquid water existed at and near the Martian surface at various time in its history. In particular, observations of the geology and mineralogy of the oldest surfaces on Mars (dating back to more than 3.8 billion years ago) provide evidence that the Martian climate was then completely different, with abundant liquid water on the surface.
At Laboratoire de Météorologie Dynamique, we have developed a numerical 3D climate model of present-day Mars, notably with the support of ESA. To better understand how the Martian climate may have allowed the formation of glaciers or rivers in the past, we have performed several investigations based on our climate model, but assuming different obliquity, orbital excentricity, or atmospheric composition, since these parameters are thought to have strongly varied in the past. These simulations unveil parts of Mars’ history, but also raise new questions.