A newly found, buried deposit of frozen carbon dioxide -- dry ice -- near the south pole of Mars contains about 30 times more carbon dioxide than previously estimated to be frozen near the pole. This map color-codes thickness estimates of the deposit derived and extrapolated from observations by the Shallow Subsurface Radar (SHARAD) instrument on NASA's Mars Reconnaissance Orbiter. The orbiter does not pass directly over the pole, and the thickness estimates for that area (with smoother transitions from color to color) are extrapolations.

Red corresponds to about 600 meters or yards thick; yellow to about 400; dark blue to less than 100, tapering to zero. The scale bar at lower right is 100 kilometers (62 miles). The background map, in muted colors, represents different geological materials near the south pole.

The estimated total volume of this buried carbon-dioxide deposit is 9,500 to 12,500 cubic kilometers (2,300 to 3,000 cubic miles).

Known variations in the tilt of Mars' rotation axis can significantly reduce or increase the proportion of the planet's carbon dioxide that is sequestered into this newly discovered deposit, climate models indicate. The Martian atmosphere is about 95 percent carbon dioxide, and this deposit currently holds up to about 80 percent as much carbon dioxide as the atmosphere does. Several-fold swings in the total mass of the Martian atmosphere can result from growing and shrinking of dry ice deposits on time scales of 100,000 years or less, the models indicate.

SHARAD was provided by the Italian Space Agency. Its operations are led by Sapienza University of Rome, and its data are analyzed by a joint U.S.-Italian science team. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the spacecraft.