Geophysical Research Letters vol:29 issue:11 pages:-
 An important characteristic of the Martian atmosphere is that a large proportion of its CO2 condensates during winter in the huge polar ice caps. This CO2 sublimation/condensation process is associated with large seasonal mass transport from the North pole to the South pole and vice versa. As the center of mass of the system-consisting of the planet and the CO2 layer-does not change due to this transport, the center of mass of the planet is displaced to satisfy the equilibrium. The effects of the planetary center of mass displacement on station positions are evaluated to be at the level of several centimeter in the direction along the rotation axis, and several millimeters in the perpendicular directions.