One of the Mars' most dramatic atmospheric features that can be spotted from orbit is the dust devil, a whirlwind of dust that forms from sunlight heating the ground. Although dust devil tracks are numerous and have been recorded many times, it can be hard to catch these whirling dervishes in the act.
BIG BIC: Twisted Twister Spotted on Mars
But in this observation from the High-Resolution Imaging Science Experiment (HiRISE) camera on board NASA's Mars Reconnaissance Orbiter, not one, but three dust devils have been shot (as in photographed).
On Earth, dust devils form when strong heating of the ground results in a warm layer of air rising through the more dense layers of air above. The air rotates faster and faster, eventually forming a swirling column that picks up dust and other lightweight debris. On Mars, dust devils form in much the same way - sunlight heats the ground and warm air rises to form swirling columns of dust that can reach several kilometers high into the thin atmosphere, much higher than their terrestrial counterparts.
ANALYSIS: Dust Devils Rip Up Mars' ‘Etch A Sketch' Surface
As shown in this observation of a region straddling Mars' equator, one well-formed dust devil is casting a long shadow across the landscape, a snapshot of its winding journey across the dusty plain. Often these aeolian features will carve out dark tracks as they travel after blowing away the brighter surface dust and exposing the darker layers.
Through observations from orbit, recording the size and frequency of dust devils can help planetary scientists better understand the characteristics of the dynamic Mars atmosphere.
"Both Mars Orbiter Camera and HiRISE images in this general region have a fairly high rate of capturing dust devils (sometimes several in one image)," writes the HiRISE science team in a recent update, "so acquiring images here in the right season has a good chance to help us obtain better measurements of these features."
Opportunity: The Amazing Self-Cleaning Mars Rover
Despite their name, dust devils are angels that come to the rescue of solar paneled robots operating on the Martian surface. Earlier this year, NASA Mars Exploration Rover Opportunity experienced a "cleaning event" that blew off much of the red dust that had stuck to the rover's solar array, boosting the solar energy it received. From experience with Opportunity and sister rover Spirit (which operated until 2010), rover scientists know that dust devils will often blow over the them, giving the lucky rovers a clean.