This interesting image from the HiRISE camera on the Mars Reconnaissance Orbiter shows a field of spectacular dunes called dune dunes. These dunes formed along a cliff in Chasma Boreale, at the North Pole of Mars.
The High Resolution Imaging Experiment, or HIRISE, is a powerful camera that takes pictures from orbit that show objects the size of a table. The image here shows an area less than 1 km (less than a mile) across, and MRO was about 197 km above the surface when the image was taken.
HiRISE scientists claim that debris dunes are common on both Earth and Mars. These dunes usually have a very distinctive shape and are important because they can tell scientists about the environment in which they formed and the direction of winds in a particular location.
Dunes form in sandy areas where winds blow in one dominant direction. This creates a crescent shaped sand dune. The arcs of sand that outline the dune dunes end in “horns” pointing downwind, while the sand is blown up the ridges and slopes. Many times this forms a shape that on top of looks like a Star Trek emblem.
The winds at the north pole of Mars must be spinning in different directions because the dunes shown above are not shaped like a classic crescent, a chevron. The image was taken using a red-green-blue filter on the camera, which gives the sand a blue appearance.
The HiRISE camera operates in the visible wavelength range, the same as the human eye, but with a telescopic lens, making it one of the highest resolution cameras in space. These high-resolution images allow scientists to distinguish objects as small as 1 meter (about 3 feet) on Mars and study surface structure far more comprehensively than any other Mars mission.
HiRISE also makes observations in the near-infrared range to obtain information about the minerals present. MRO has been orbiting Mars since 2006, and the length of the mission means that planetary scientists can track changes over time. The purpose of taking the lead image is for the team to track the seasonal changes in that region over time.