A recent video compiled of imagery from NASA’s Mars Reconnaissance Orbiter (MRO) shows that—far from the dead planet that Mars was once believed to be—the Red Planet is a very active world.
Since arriving at Mars in March 2006, the spacecraft has observed changes to the sand dunes located in the far north of the planet affected by frozen carbon dioxide. One of the processes by which the carbon dioxide on Mars travels around the planet is called sublimation. On Earth, the cycle in which water moves from one state to another is well known: ice melts to become a liquid, and then the liquid evaporates to become a vapor. Sublimation skips the middle man. Ice moves directly into a vapor without becoming a liquid.
The seasonal processes on Mars are shaped by this process when gas moves up from under the ice, sand, and dust, forming streaks and fans. The patterns, however, don’t remain. Once again, the changeable Martian weather—in this case, the winds—clears the landscape.
Video courtesy of NASA / JPL
“It’s an amazingly dynamic process,” said Candice Hansen of the Planetary Science Institute, Tucson. “We had this old paradigm that all the action on Mars was billions of years ago. Thanks to the ability to monitor changes with the Mars Reconnaissance Orbiter, one of the new paradigms is that Mars has many active processes today.”
Some of the most evident effects of these processes are transient grooves that form on dunes. These are created when gas trapped under the ice finds a path to the surface and rushes out into the atmosphere. The gas carries sand along with it, and this sand forms fans and streaks across the frost and ice on the surface.
It is these dynamic and ever-changing cycles that have changed the way scientists now view the Red Planet. It also reinforces both the similarities as well as the dramatic differences between Mars and our home world. The outrushing of gases causes patterns to form on the southern dunes that NASA has dubbed “spiders.” For some reason, these patterns have not yet been seen in the north. One reason could be the different types of terrain that are present in the north as compared to the south. The south has a variety of terrains, including the flat areas that the “spiders” call home. The north, by contrast, is comprised primarily of a swath of dunes that surrounds the permanent ice cap.
“It is a challenge to catch when and how those changes happen—they are so fast,” said Ganna Portyankina of the University of Bern in Switzerland and a lead author of the reports written about the phenomena. “That’s why only now we start to see the bigger picture that both hemispheres actually tell us similar stories.”
MRO’s High Resolution Imaging Science Experiment (HiRISE) has gained six years of information from its vantage point high above the valleys and craters of Mars; it has spent that time recording the seasonal changes taking place below. In the Martian spring, bursts of gases have been seen carrying sand. The winter ice has been viewed cracking atop the endless dunes and sand has been recorded tumbling down those dunes.