Fig. 7

Surface methane mixing ratio (output from the first vertical model level at 10 m) in the vicinity of the MSL in logarithmic scale, both during nighttime (0:00 h LTST) and daytime (12:00 h LTST) produced by two different sources at different locations (locations 18 and 47) relative to the MSL (represented by a black dot). The emission area is represented by a square. Both emission sources present similar methane abundances, in accordance with MSL’s observations (~ 1 ppbv or less, Webster et al. 2018) during nighttime; however, the unfavorable air mass transport during the night for the northwestern emission source (location 47, bottom panels) requires a much higher emission flux to match MSL’s observations. It implies that the extremely favorable anabatic flows blowing over the slopes of Aeolis Mons, and the development of the planetary boundary layer, during daytime, produce a sustainable increase in the methane abundance at MSL’s location to values of the order of 100 ppbv, which is not what has been observed at all (Webster et al. 2015; 2018)