air and the winds which are weaker than Earth winds. It may be due to "saltation" - ballistic movement of sand grains which travel further in the weaker Mars gravity. The lee fronts of the dunes in this region move on average 0.5 meters per year (though the selection may be biased here as they only measured dunes with clear lee edges to measure) and the ripples move on average 0.1 meters per year. Gallery See also List of mountains on Mars by height References External links Syrtis Major map at Google Mars Albedo features on Mars Mountains on Mars Shield volcanoes Volcanoes of Mars Mars 2020 Syrtis Major quadrangle