One of the primary objectives for the Mars Global Surveyor (MGS) Mars Orbiter
Camera (MOC) during the Extended Mission is to continue daily monitoring of
martian weather as expressed in clouds, dust storms, and patches of polar frost.
During the Primary Mission, which lasted from March 1999 through January 2001,
changes that occurred over a single martian year (687 Earth days) were observed.
Now it is possible to see what the martian atmosphere will do for at least two-thirds
of a second martian year, because the Extended Mission will run into April 2002.
This picture captures two dust storms, each large enough to cover Arizona or New
Mexico. One is located near the lower left, the other at the lower right. Taken on
April 8, 2001 (mid-southern winter), this is a mosaic of six MOC daily global images
centered around Hellas Planitia in the martian southern hemisphere. Hellas Planitia
is the dominant elliptical feature just below the center of the picture. The bright,
nearly white surfaces along the lower (southern) edge of the picture are covered
by wintertime frost. The strong temperature difference between the winter frost
and the warmer air just off the edge of this polar cap generates winds that---at this
time of year---are often strong enough to lift dust into large, reddish-brown,
North is up and sunlight illuminates the area from the upper left. The martian
equator forms the arc along the top of the picture; 500 kilometers (km) is equal to
about 311 miles. The approximately 500 kilometer-wide circular feature just above
the center is the crater Huygens.
Image Credit: NASA/JPL/Malin Space Science Systems
Full Res Image