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VIDEO: Twister on Mars!

AN AFTERNOON WHIRLWIND on Mars lofts a twisting column of dust more 800 metres into the air in this image from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter.

HiRISE captured the image on February 16, 2012, while the orbiter passed over the Amazonis Planitia region of northern Mars. In the area observed, paths of many previous whirlwinds, or dust devils, are visible as streaks on the dusty surface.

The active dust devil displays a delicate arc produced by a westerly breeze partway up its height. The dust plume is about 30 metres in diameter.

The image was taken during the time of Martian year when that planet is farthest from the Sun. Just as on Earth, winds on Mars are powered by solar heating. Exposure to the Sun’s rays declines during this season, yet even now, dust devils act relentlessly to clean the surface of freshly deposited dust, a little at a time.

Dust devils occur on Earth as well as on Mars. They are spinning columns of air, made visible by the dust they pull off the ground. 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 Mars Reconnaissance Orbiter has been examining Mars 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.

Adapted from information issued by Guy Webster, Jet Propulsion Laboratory NASA / JPL-Caltech / University of Arizona.

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Otherworldly artwork

Dust devil tracks on Mars

Tracks left by dust devils moving across the Martian dune plains.

These amazing patterns were spotted in the northern hemisphere of Mars on August 24, 2009 by the HiRISE camera aboard NASA’s orbiting Mars Reconnaissance Orbiter (MRO) spacecraft.

They are the tracks left by dust devils—mini tornadoes—moving across the Martian dunes.

Satellite image of a Martian dust devil

Looking down on a Martian dust devil...the small, round fuzz ball near the bottom left corner. The shadow cast by the devil can be seen to its left.

Take a look at the high-resolution version (will open in a new window or tab) of the image—it’s quite amazing.

Dust devils form when the Sun heats the surface so that the ground is warm to the touch, even though the atmosphere at 2 metres (6 feet) above the surface would be chilly. That temperature contrast causes convection (rising air) to where the wind speed is slightly higher. Mixing the dust, winds, and convection triggers the dust devils.

Scientists use images of dust devils to study several things. Tracking the devils shows which way the wind blows at different times of day. Statistics on the size of typical dust devils will help with estimates of how much dust they pump into the atmosphere every day. And by watching individual devils change as they go over more-dusty and less-dusty terrain, researchers can learn about the turbulent motion near the surface. Ultimately, that motion of wind and dust near the surface relates these small dust devils with Mars’ much larger dust storms.

MRO was 285 kilometres above the Martian surface at the time it took the image, which shows detail down to about 1.7 metres resolution.

The video below shows the progress of a dust devil moving across the plains in full view of the Spirit lander. The sequence of images spans a period of 9 minutes and 35 seconds, but has been speeded up for the purposes of the video.

Adapted from information issued by NASA / JPL-Caltech / Cornell University / Texas A&M / University of Arizona.

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