Martian dust devil

A dust devil is a term for a relatively small swirl of air with dust trapped in it so that it is visible. They are normally not very big. A Martian dust devil roughly 12 miles high was captured whirling its way along the Amazonis Planitia region of Northern Mars on March 14. It was imaged by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. Despite its height, the plume is little more than three-quarters of a football field wide (70 yards, or 70 meters). Unlike a tornado, a dust devil typically forms on a clear day when the ground is heated by the sun, warming the air just above the ground. As heated air near the surface rises quickly through a small pocket of cooler air above it, the air may begin to rotate, if conditions are just right. The image was taken during late northern spring, two weeks short of the northern summer solstice, a time when the ground in the northern mid-latitudes is being heated most strongly by the sun. A dust devil on Earth is a strong, well-formed, and relatively long-lived whirlwind, ranging from small (half a meter wide and a few meters tall) to large (more than 10 meters wide and more than 1000 meters tall). Dust devils also occur on Mars (see Dust Devil Tracks) and were first photographed by the Viking orbiters in the 1970s. In 1997, the Mars Pathfinder lander detected a dust devil passing over it. Martian dust devils can be up to fifty times as wide and ten times as high as terrestrial dust devils, and large ones may pose a threat to terrestrial technology sent to Mars. The Mars Reconnaissance Orbiter has been examining the Red Planet with six science instruments since 2006. Now in an extended mission, the orbiter continues to provide insights into the planet's ancient environments and how processes such as wind, meteorite impacts and seasonal frosts continue to affect the Martian surface today. This mission has returned more data about Mars than all other orbital and surface missions combined. More than 21,700 images taken by HiRISE are available for viewing on the instrument team's website: http://hirise.lpl.arizona.edu.