The latest pictures of the Red Planet show sand dunes, which are not unusual to see up there, but there are in the shape of perfect circles. READ MORE: Putin's scientists hunt for 'interstellar dust' in one million-year-old frozen lakeThe space agency's Mars Reconnaissance Orbiter (MRO) spotted the shapes as it studied how frost thaws at the end of Martian winter. NASA explains: "Sand dunes of many shapes and sizes are common on Mars. That quirky image was taken in December from a height of 251 km, with NASA saying: "A Bear on Mars? Ariz/SWNS)Mars Reconnaissance Orbiter has been orbiting and studying Mars since 2006.