Empirical Estimates of Martian Surface Pressure in Support of the Landing of Mars Science Laboratory

The aim of this work is to develop an empirical expression for diurnal mean martian surface pressure in support of the landing of Mars Science Laboratory. We evaluate the consistency of surface pressure measurements from four landers, Viking Lander 1, Viking Lander 2, Mars Pathfinder, and Phoenix, and one radio occultation experiment, Mars Global Surveyor. With the exception of Mars Pathfinder, whose measurements are 0.1 mbar smaller than expected, all are consistent. We assume that the diurnal mean surface pressure is a separable function of altitude and season, neglecting dependences on time of day, latitude, and longitude, and use the Viking Lander 1 dataset to characterize the seasonal dependence as a harmonic function of season with annual and semi-annual periods. We characterize the exponential dependence of surface pressure on altitude using Mars Global Surveyor radio occultation measurements widely-distributed below +1 km altitude and within 45 degrees of the equator. These measurements have local times of 3-5 hours, which may introduce biases into our estimates for diurnal mean surface pressure. Our empirical expression for diurnal mean surface pressure, p (dm) , is p (0,VL1)exp(-(z-z (0,VL1))/H (0)) (1+s (1,VL1)sin(1L (s) )+c (1,VL1)cos(1L (s) )+s (2,VL1)sin(2L (s) )+c (2,VL1)cos(2L (s) )) where z is altitude, L (s) is season, the reference pressure, p (0,VL1), is 7.972 mbar, the altitude of Viking Lander 1, z (0,VL1), is -3.63 km, the reference scale height, H (0), is 11 km, and the harmonic coefficients are s (1)=-0.069, c (1)=0.060, s (2)=0.045, and c (2)=-0.050. We validate this expression against the available datasets and estimate, with a 1-sigma confidence level of 2 %, a diurnal mean surface pressure of 7.30 mbar at Gale Crater, the Mars Science Laboratory landing site, at L (s) =150A degrees.