Mars Picture of the Day: Two Mars Years of South Polar Change

Mars Global Surveyor Mars Orbiter Camera

MGS MOC Release No. MOC2-367, 21 May 2003

NASA/JPL/Malin Space Science Systems

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. Comparision 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.

Malin Space Science Systems and the California Institute of Technology
built the MOC using spare hardware from the Mars Observer mission.
MSSS operates the camera from its facilities in San Diego, California.
The Jet Propulsion Laboratory’s Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena,
California and Denver, Colorado.