Corduroy Dunes
Jet Propulsion Laboratory https://www.jpl.nasa.gov/ May 29, 2018
This image from NASA's Mars Reconnaissance Orbiter (MRO) shows the permanent polar cap of Mars, encircled by sand dunes and looking like pulled threads, these dunes march across a fabric of patterned ground.
At this time of the Martian year the dunes are free of the seasonal dry ice that forms a temporary cover every winter.
The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.