Martian surface pressure

Martian surface pressure

Fig. 8.7 . Daily mean surface pressures at the two Viking Lander, denoted VL, sites recorded for one Martian year, showing that the red planet periodically removes and replaces large amounts of carbon dioxide in its atmosphere. The seasons are for the northern hemisphere, and the pressure is given in millibars, abbreviated, mb, where 1 mb = 0.001 bar and 1 bar is the sea-level pressure of the Earth’s atmosphere. At the Viking 1 site (bottom curve), the pressure ranged from 6.7 mb during the northern summer to 8.89 mb at the commencement of northern winter. At the Viking 2 site (top curve) the equivalent data were 7.4 mb and 10 mb. The higher values are probably due to the lower elevation; there was an approximate 1.1-kilometer difference in the elevation of the two landing sites. Dust storms are thought to produce some of the smaller non-seasonal pressure variations. The seasonal pressure differences seem to be dominated by the southern polar cap, which is larger than the northern one. In the southern winter, and northern summer, carbon dioxide is condensed out of the atmosphere, enlarging the southern polar cap and reducing the total surface pressure of the planet. In southern summer, and northern winter, the carbon dioxide has been released back into the atmosphere, with an increase in the total surface pressure.

Copyright 2010, Professor Kenneth R. Lang, Tufts University