One of the science objectives of this observation was to try to capture the same dust devil in both cameras simultaneously by coordinated HiRISE and MER Spirit observations.

Surprisingly few dust plumes and dust devil tracks have been observed by HiRISE in Gusev Crater, in comparison to the number of dust devils seen by the rover. Obtaining both ground-based and orbital imagery will allow scientists to better understand the formation, physical properties, and behavior of the dust devils at the MER Spirit landing site.

During these coordinated observations, Spirit observed several small dust devils and a large dust devil in the flat plains northwest of its current position on the western scarp of a polygonal feature commonly called Home Plate. On the other hand, the HiRISE camera did not detect an active dust devil nor the track that dust devils often leave behind. However, a dust devil plume was captured east of Columbia Hills that was about 17 meters in diameter! The top “L-curve” is the track left behind, and the bottom “L-curve” is the shadow of the plume. With changing winds, the dust devil is moving in a direction different than when it formed. It may be that only the largest of the Gusev Crater dust devils can be easily seen by HiRISE.

BACKGROUND
Ground-based (Mars Exploration Rover) MER and orbital MRO (Mars Reconnaissance Orbiter) HiRISE observations indicate that the low albedo zone in Gusev Crater is currently an active area for the formation of dust devils.

Dust devils are convecting warm-core vortices that form when hot surface air rises and is replaced by the radial inflow of surrounding cool air. This rising vertical column of swirling warm air creates a low pressure core. The low pressure core acts like a vacuum that picks up fine particles that mantle the surface and exposes the dark basaltic substrate in a narrow track.

Subimage credit: Devin Waller, Arizona State University (for Spirit coordination).



Written by: Circe Verba  (2 September 2009)