<P> The south polar permanent cap is much smaller than the one in the north . It is 400 km in diameter, as compared to the 1100 km diameter of the northern cap . Each southern winter, the ice cap covers the surface to a latitude of 50 ° . Part of the ice cap consists of dry ice, solid carbon dioxide . Each winter the ice cap grows by adding 1.5 to 2 meters of dry ice from precipitation from a polar - hood of clouds . In summer, the dry ice sublimates (goes directly from a solid to a gas) into the atmosphere . During each year on Mars as much as a third of Mars' thin carbon dioxide (CO) atmosphere "freezes out" during the winter in the northern and southern hemispheres . Scientists have even measured tiny changes in the gravity field of Mars due to the movement of carbon dioxide . In other words, the winter buildup of ice changes the gravity of the planet . Mars has seasons that are similar to Earth's because its rotational axis has a tilt close to our own Earth's (25.19 ° for Mars, 23.45 ° for Earth). The south polar cap is higher in altitude and colder than the one in the north . </P> <P> The residual southern ice cap is displaced; that is, it is not centered on the south pole . However, the south seasonal cap is centered near the geographic pole . Studies have shown that the off center cap is caused by much more snow falling on one side than the other . On the western hemisphere side of the south pole a low pressure system forms because the winds are changed by the Hellas Basin . This system produces more snow . On the other side, there is less snow and more frost . Snow tends to reflect more sunlight in the summer, so not much melts or sublimates (Mars climate causes snow to go directly from a solid to a gas). Frost, on the other hand has a rougher surface and tends to trap more sunlight, resulting in more sublimation . In other words, areas with more of the rougher frost are warmer . </P> <P> Research, published in April 2011, described a large deposit of frozen carbon dioxide near the south pole . Most of this deposit probably enters Mars' atmosphere when the planet's tilt increases . When this occurs, the atmosphere thickens, winds get stronger, and larger areas on the surface can support liquid water . Analysis of data showed that if these deposits were all changed into gas, the atmospheric pressure on Mars would double . There are three layers of these deposits; each is capped with a 30 - meter layer of water ice that prevents the CO from sublimating into the atmosphere . In sublimation a solid material goes directly into a gas phase . These three layers are linked to periods when the atmosphere collapsed when the climate changed . </P> <P> A large field of eskers exist around the south pole, called the Dorsa Argentea Formation, it is believed to be the remains of a giant ice sheet . This large polar ice sheet is believed to have covered about 1.5 million square kilometers . That area is twice the area of the state of Texas . </P>

Studies have shown that the ice located in the south pole of mars is mostly