MGS MOC Release No. MOC2-367, 21 May 2003
Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images acquired in 1999 and 2001 suggested that each Mars year, for the past several hundred years (if not thousands), the layered carbon dioxide ice of the south polar residual cap has been disappearing. Scarps formed by sublimation of these icy layers retreat at an average rate of about 3 meters (~3 yards) per Martian year.
MOC is now in its third Mars year of detailed exploration of the red planet. Recently, southern spring began, and the south polar cap emerged from winter darkness. The first picture shown here (top) was obtained by MOC less than a week ago (May 2003). The second picture shows the same area of the south polar residual cap, as it appeared 2 Mars years earlier in August 1999. Comparison shows that, between 1999 and 2003, several small mesas and buttes vanished, holes grew larger, and more cracks and pits appeared as carbon dioxide was removed from the polar cap.
The image pair is located near 86.8°S, 109.0°W. Sunlight illuminates both from the upper right. One Mars year is about 687 Earth days long.