Lander Altitude

The higher the landing site, the less than pressure (Updated 3/24/2019)

On Earth there is a loss of about 1 inch of mercury (about 33.86 mbar) for each thousand feet ascended.  Lander altitude and latitude can have an impact on pressure readings, and must be compensated for when comparing mission pressure readings. The source for the information below is a draft copy of a paper by Peter A. Taylor, et. al. (October 20, 2009) entitled On Pressure Measurement and Seasonal Pressure Variations during the Phoenix Mission.  Because Pathfinder is at a higher altitude, its minimum pressure was adjusted from 670 Pa (6.7 mbar) to 698 Pa.  They state that Viking 1 amplitudes are increased by a factor of 1.0455 to compare them with the Phoenix values (Viking 1 was higher, so it feels less air pressure than Phoenix) while Viking 2 values should be reduced by a factor of 0.967 to compare with Phoenix (Viking 2 was lower than Phoenix, so it should feel more pressure than Phoenix).  The paper listed the mean (adjusted) pressure at sites as follows: Viking 1 year A = 7.936 mbar, Viking 1 Year B = 7.942 mbar and Phoenix 8.326 mbar.  Again, the above Pathfinder pressure was listed not as a mean, but rather as a minimum.