This broad field of barchan sand dunes – dunes with crescent shapes – in the Olympia Undae region near Mars’ northern polar cap was imaged by NASA’s Mars Odyssey orbiter. The image, showing a small segment of the dune field, was taken during summer when the surface was free of frost. The dunes cover an area of some 470,000 square kilometres (181,000 square miles), larger than the U.S. state of California, and surround about a quarter of the northern polar cap. It is the most expansive continuous field of dunes on Mars.
With just a month to go until the 2016 opposition of Mars, the Red Planet is now visible very low in the southeast before midnight for observers in the heart of the UK. Mars and ringed planet Saturn are presently separated by just over 7 degrees — a low power, wide-angle binocular field of view. The waning gibbous Moon passes by on the mornings of 25—26 April.