The rate of movement for 3- and 10-cm-high granule ripples was documented in September of 2006 at Great Sand Dunes National Park and Preserve during a particularly strong wind event. Impact creep induced by saltating sand caused ~24 granules min-1 to cross each cm of crest length during wind that averaged ~9 m s-1 (at a height well above 1 m), which is substantially larger than the threshold for saltation of sand. Extension of this documented granule movement rate to Mars suggests that a 25-cm-high granule ripple should require from hundreds to thousands of Earth-years to move 1 cm under present atmospheric conditions.
Zimbelman, James R., Irwin, Rossman P., III, Williams, Steven H., Bunch, Fred, Valdez, Andrew and Stevens, Scott. 2009. The rate of granule ripple movement on Earth and Mars. <i>Icarus<i>, 203(1): 71-76. doi:10.1016/j.icarus.2009.03.033