"Dark sand dunes and inverted craters in the Arabia Terra region of Mars ... where erosion has stripped away surrounding topography"
"Carbon dioxide ice forms an uninterrupted layer in winter. ... dark streaks form on the dunes as surface material from below the ice is mobilized and deposited on top of the ice."
"Barchan sand dunes that form in wind regimes ... The ridged arcs of sand end in horns that point downwind."
"Sand dunes. The swirls are caused by dust devils, which are like mini-tornadoes."
"A 2-mile thick sequence of ice and dust ... covers the south pole of Mars. Once ice begins to melt, darker dustier material appears."
"A series of semi-parallel fissures on Mars, known as Cerberus Fossae, formed by faults which pulled the crust apart in the region."
The Mars Reconnaisance Orbiter has completed its fourth year in operation, having been launched on August 12th 2005; it entered orbit around Mars on March 10th 2006. The spacecraft is apparantly continuing its investigation of Mars' surface, subsurface and atmosphere. An onboard 'ground penetrating radar' has sampled half the planet and findings proved that water existed (at least regionally) on and near the planet's surface for hundreds of millions of years. Findings could also potentially reveal evidence of past life, "if it ever existed".