Cold pool pockets develop at the bottom of Gale crater (Mars)

The Curiosity rover has moved more than 31 km from the landing site at the very bottom of the crater and has climbed more than ∼750 m into the Mnt. Sharp foothills over more than five Martian years. A significant change in temperatures and pressures measured by the REMS monitoring weather station aboard the Curiosity rover has been detected during that traverse.
On Earth deep valleys, like the ones in Alps, and craters on Mars like Gale accumulate masses of cold air at night, a.k.a. cold pools, at the bottom of the craters. These pockets of cold air change aspects of local micrometeorology at the bottom of a deep valley compared to the slopes. Downslope winds originating from both Mnt. Sharp and crater rims converge at the very bottom of the crater floor and may produce a vortex in the very stable and shallow nocturnal air mass [Rafkin et al. 2016]. This flow would prevent the nighttime accumulation of any tracer along the slopes above the cold pool and facilitate the convergence and accumulation of tracers in the bottom of the crater. The exception is during the northern hemisphere winter (around Ls 270 when strong northerly winds tend to scour the crater air mass day and night [Pla-García et al. in 2019].
As Curiosity ascends, we can examine whether these cold air masses exist at the very bottom of the crater and whether the rover moves away from them when reaching a specific height through Mnt. Sharp slopes. One indication is an increase in nighttime temperatures as the rover climbs Mt. Sharp’s slope. Those interannual increments of nighttime temperatures at Gale show a smooth variation within the lower layers before changing scenarios from landing location and tosol’s (Figure). To distinguish this effect from seasonal trends, an analysis of potential temperatures was performed (Figure). Comparing minimum to average temperatures in Figure allows to relate the changes to seasonal or other effects. The figure shows the annual evolution of the Martian air temperature using a Fourier adjustment. Modeling and observations strongly suggest that the rover has ascended to elevations above the cold pool at the bottom of the crater [Ruíz-Pérez et al. 2024 in preparation].