NASA / JPL-Caltech / Univ. of Arizona
A towering dust devil casts a serpentine shadow over the Martian surface in this image, acquired on Feb. 16 by the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter.
A Martian mini-tornado caught on camera by NASA's Mars Reconnaissance Orbiter brings new meaning to the word "twister."
This isn't the first dust devil to show up on Martian imagery. The whirlwinds have been photographed by NASA probes for more than 30 years, and in some places, the Red Planet's landscape is heavily crisscrossed by dust devil tracks. In 2005, the Spirit rover's time-lapse view of multiple dust devils was made into a movie. But this picture, taken on Feb. 16 as the orbiter passed over the Amazonia Planitia region of northern Mars, has to rank among the most artistic of the dust devil delights.
Scientists estimate that the dust devil rose to a height of more than half a mile (800 meters), with a plume that's about 30 yards (meters) in diameter. A westerly breeze adds a delicate arc to the plume, and the afternoon sun creates a curving, stretched-out shadow.
Dust devils on Mars, like their cousins on Earth, are spinning columns of air that are made visible by the dust they stir up. They typically arise on a clear day when the ground is heated by the sun. As the atmospheric layer near the surface warms, air rises through a pocket in the cooler layer above it, taking on a spin when the conditions are just right.
Martian air is much thinner than our earthly atmosphere, and composed almost entirely of carbon dioxide. But the Red Planet's winds can still pack a huge punch. Over the years, NASA's rovers have benefited from wind-driven "cleaning events" that sweep the dust off their power-generating solar panels. Last month, the Opportunity rover underwent a slight cleaning that put it in a better position to endure the Martian winter — which just goes to show that a devil can be an angel on the Red Planet.
More from Mars:
- The Mars rover stays in the picture
- Watch a dust devil spin in the Martian arctic
- Slideshow: Greatest hits from the Red Planet
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.