Using images of sand dunes on Mars captured by NASA's Mars Reconnaissance Orbiter, a group of planetary scientists have shown that some of these structures migrate.
Focussing on two regions on the Red Planet, right near the equator, they found that sprawling heaps of sand which they term as "megaripples" make stealthy movements from point to point of the Martian surface. Sometimes, these dunes move slow enough that it could easily escape one's notice in visuals and maps.
The team poured through images of two sites on Mars. Almost 1,100 of these "megaripples" were seen the McLaughlin crater " a complex crater around 92km wide that formed on Mars some 4 billion years ago, from images taken 7.6 years apart. Another 300 of these shifting sands were seen in the Nili Fossae region which is one of the most enigmatic regions on Mars, from images taken 9.4 years apart.
In both regions, they found were multiple signatures of movement in time-lapse images of each site taken years apart. These megaripples appeared to be moving at a crawling rate of about 10 centimeters every year, as per the study published in the Journal of Geophysical Research: Planets.
Modern bedforms on Mars called megaripples, seen in this 2019 MRO image, have likely been active over long timescales and have migrated in the recent past. Image: Mars Reconnaissance Orbiter/NASA
This discovery goes against some long-held beliefs about textured dunes on Mars being stationary, about this "megaripples" haven't moved since they formed many hundreds to thousands of years ago.
Some researchers are surprised that these Martian megaripples move at all. As of decades ago, there was no evidence to show that sands on Mars were mobile, planetary geologist at the Smithsonian Institution's Air and Space Museum, Jim Zimbelman told Science.
"None of us thought that the winds were strong enough."