Microscopic liquid brines , especially calcium-perchlorate could emerge by deliquescence on Mars during night time hours .
Using climate model computations and orbital humidity observations , the ideal periods and their annual plus daily characteristics at various past , current and future landing sites were compared .
Such results provide context for future analysis and targeting the related observations by the next missions for Mars .
Based on the analysis , at most ( but not all ) past missions ’ landing sites , microscopic brine could emerge during night time for different durations .
Analysing the conditions at ExoMars rover ’ s primary landing site at Oxia Planum , the best annual period was found to be between L _ { s } 115 - 225 , and in Local \hskip { 2.845276 pt } Time 2 - 5 , after midnight .
In an ideal case , 4 hours of continuous liquid phase can emerge there .
Local conditions might cause values to differ from those estimated by the model .
Thermal inertia could especially make such differences ( low TI values favour fast cooling and \textrm { H } _ { 2 } \textrm { O } cold trapping at loose surfaces ) and the concentration of calcium-perchlorate salt in the regolith also influences the process ( it might occur preferentially at long-term exposed surfaces without recent loose dust coverage ) .
These factors should be taken into account while targeting future liquid water observations on Mars .