A dune field on Mars, as seen by the Mars Reconnaissance Orbiter. (Image credit: NASA/JPL-Caltech/University of Arizona)Are those purple, wavy, alien thumbprints? Or perhaps an otherworldly ocean? Nope! It's actually a dune field on Mars, colored purple.What is it?Across the Martian surface are all sorts of unique features in the rocky, dusty surface material. In this false-color image, snapped by the HiRISE (High Resolution Imaging Science Experiment) camera on NASA's Mars Reconnaissance Orbiter, you can see the incredible and strange ripples of a dune field on Mars."Our science goal for this observation is to observe any changes from a previous image we acquired in 2011," a statement sharing the image reads. "For this footprint, the target enlarged and centered more over the dune field, which is located on the floor in the northern half of an unnamed impact crater."Why is it incredible?Spacecraft like MRO, with its HiRISE camera, have opened our eyes to the incredible features across the Martian surface. From dune fields like we see here to craters and ancient riverbeds, these views have helped scientists piece together the planet's incredible, dynamic history. For decades, observations from orbit around Mars and by rovers on the planet's surface have helped to solve at least part of the mystery of what Mars was once like. Researchers are still looking for signs that unequivocally point to life once existing on the planet. But so far, observations have showed that, billions of years in the past, Mars had abundant surface water — lakes, rivers perhaps even a huge ocean. In analyzing the material in and near ancient waterways on the planet with NASA's Perseverance rover, researchers have already found evidence that could possibly link to biosignatures. While this image might look like a strange but beautiful purple-colored desktop background, photos like it this can be essential clues for scientists hunting for answers.