Dust devils are a regular feature on Mars. Just like those found on Earth, these mini whirlwinds form when parts of Mars are warmed by the Sun, causing air above the surface to swirl upward, carrying dust with it. But in Mars' lower gravity (38% that of Earth), these devils grow much larger, reaching up to 8 km (5 mi) in height and achieving speeds of up to 45 meters per second (150 ft/s). They are also a major part of Mars' meteorological cycles, playing a key role in distributing dust across the planet.

When passing above Mamers Valles, a set of channels in a winding canyon system etched into the cratered northern uplands of Arabia Terra, the ESA's Mars Express probe spotted dozens of active dust devils. The image (shown above) was taken by the High Resolution Stereo Camera (HRSC), one of eight instruments aboard the *Mars Express* that has been mapping the surface of the Red Planet since 2003.

The image (at top) was created by combining sequential views from the High Resolution Stereo Camera (HRSC), using up to nine separate camera channels. The alignment and integration of the HRSC's various camera channels enable scientists to detect anything moving on the surface and determine the direction and speed of dust devils. The channels in Mamers Valles extend for around 1,000 km (660 mi) from Mars's ancient southern highlands into the planet's northern lowlands and measure up to 25 km (15.5 mi) in diameter and 1.2 km (0.75 mi) deep.

They are surrounded by multiple features of interest, including mesas, cliffs, and glaciers of water ice buried beneath dust and debris. Some of the channels are lined with dark material, which is believed to be volcanic sands, some of which may have been deposited by wind. Many of these features are indications that water once flowed through this region, as well as lava or ice, depending on the time period. This is consistent with the valley's age, which is dated to the late Noachian period (ca. 3.8 billion years ago).

It was during this geological epoch that Mars began to transition from a warmer, wetter, geologically active planet to the extremely cold, desiccated, and (largely) geologically inert world it is today.

Further Reading: ESA