The Surface Stereo Imager on NASA's Phoenix Mars Lander caught this dust
devil in action west of the lander in four frames shot about 50 seconds
apart from each other between 11:53 a.m. and 11:56 a.m. local Mars time on
Sol 104, or the 104th Martian day of the mission, Sept. 9, 2008.
Dust devils have not been detected in any Phoenix images from earlier in
the mission, but at least six were observed in a dozen images taken on Sol
104.
Dust devils are whirlwinds that often occur when the Sun heats the surface
of Mars, or some areas on Earth. The warmed surface heats the layer of
atmosphere closest to it, and the warm air rises in a whirling motion,
stirring dust up from the surface like a miniature tornado.
The dust devil visible in this sequence was about 1,000 meters (about
3,300 feet) from the lander when the first frame was taken, and had moved
to about 1,700 meters (about 5,600 feet) away by the time the last frame
was taken about two and a half minutes later. The dust devil was moving
westward at an estimated speed of 5 meters per second (11 miles per hour),
which is similar to typical late-morning wind speed and direction
indicated by the telltale wind gauge on Phoenix.
This dust devil is about 5 meters (16 feet) in diameter. This is much
smaller than dust devils that have been observed by NASA's Mars
Exploration Rover Spirit much closer to the equator. It is closer in size
to dust devils seen from orbit in the Phoenix landing region, though still
smaller than those..
The image has been enhanced to make the dust devil easier to see. Some of
the frame-to-frame differences in the appearance of foreground rocks is
because each frame was taken through a different color filter.
The Phoenix Mission is led by the University of Arizona, Tucson, on behalf
of NASA. Project management of the mission is by NASA's Jet Propulsion
Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin
Space Systems, Denver.