Did you know that Transverse Aeolian Ridges (or TARs) are small aeolian bedforms that are distinct from typical dunes or ripples. They can be found all over Mars, and are typically located near layered terrains, or near fields of large dark dunes.
TARS form perpendicular to the wind direction and are thought to be composed of coarse-grained material. They also appear to be hardened and may be much less mobile than the larger dunes.
This image depicts such a TAR in Syrtis Major, which is largely devoid of dust.
The TARs depicted in this scene possess a highly unusual morphology. Instead of single ridges, we see sets of small ridges that are separated by about 50 meters. The smaller ripples are spaced only 5 to 8 meters apart. Between the smaller ripples are even smaller striations that are perpendicular to the ridge crests with regular spacings of less than 2 meters.
Image Credit: NASA/JPL/University of Arizona (download full size image)