"Dry areas created by global circulation patterns contain most of the deserts on the Earth. The deserts of our world are not restricted by longitude, latitude, or elevation. They occur from areas close to the poles down to areas near the equator. … Deserts are not confined to earth. The atmospheric circulation patterns of other terrestrial planets with gaseous envelopes also depend on the rotation of those planets, the tilts of their axes, their distances from the Sun and the composition and density of their atmospheres. Except for the poles the entire surface of Mars is a desert. Venus may also support deserts ."