images

Mars: south polar cap

by

Nasa/JPL/MSSS/Novapix

Reference

a-mar06-00270

Date

2006-10-11

This is the south polar cap of Mars as it appeared to the Mars Global Surveyor on April 17, 2000. In winter and early spring, this entire scene would be covered by frost. In summer, the cap shrinks to its minimum size, as shown here. Even though it is summer, observations made by the Viking orbiters in the 1970s showed that the south polar cap remains cold enough that the polar frost (seen here as white) consists of carbon dioxide. Carbon dioxide freezes at temperatures around -125° C (-193° F). The polar cap from left to right is about 420 km (260 mi) across.