Martian Dune Fields Change at Varied Speeds

The famous sand dunes of Mars have been among the first structures to be observed on the planet when its exploration began, and experts until now believed that the sand masses were frozen in time. A new study shows that, in fact, the dunes can shift at both low and high speeds.

In the new investigation, experts focused their attention on the northern hemisphere of Mars, where previous studies identified extensive sand dune fields, covering an area the size of Texas.

All of these structures were concentrated in a ring-like structure on the Red Planet, located just underneath the northern polar cap. In fact, the dune fields occupy what can best be described by a latitude line underneath the Martian ices.

In studies conducted thus far, investigators determined that the dunes were fixed, maybe even sporting a crust on their surfaces. Geologists and planetary scientists hypothesized that the objects could have been relics from the planet's distant, more geologically-active past.

At the time, the winds that led to the formation of the sand dunes were a lot stronger than they area today, the thinking went. But recent photographs by a NASA spacecraft turned that view on its head.

Experts operating the Mars Reconnaissance Orbiter (MRO) conducted a study on the dunes in which they imaged them at one point in time, and then two Martian years later. This is the time-equivalent of four years here on Earth.

“The magnitude of the changes we saw were really surprising,” explains Candice Hansen, who holds an appointment as a planetary scientist at the Tucson, Arizona-based Planetary Science Institute.

The expert is also the deputy principal investigator of the MRO High Resolution Imaging Science Experiment (HiRISE) camera, and the lead co-author of a new study detailing the findings.

The work was published in the February 4 issue of the top journal Science. The MRO study included taking both black and white, and false-color images of the same area, but over different time spans.

“The first year we were looking at the HiRISE images, it was tempting to say there were changes, but it wasn't until the second year that we had something to compare our first results to,” Hansen explains.

Experts discovered that part of the dune movement patterns were caused by the seasonal sublimation and freezing of dry ice, whereas the other parts were accounted for by strong gusts of wind.

“This [carbon dioxide] gas flow destabilizes the sand on Mars' sand dunes, causing sand avalanches and creating new alcoves, gullies and sand aprons on Martian dunes,” the HiRISE investigator says.

“The level of erosion in just one Mars year was really astonishing. In some places, hundreds of cubic yards of sand have avalanched down the face of the dunes,” Hansen concludes, quoted by Space.