Dunes + Craters = Mars

A Piece of Mars: How do you tell when a planetary landscape shows Mars, instead of Mercury or the Moon or Europa? The easiest way to tell is to look for both craters and dunes, like what’s shown here in this 640×360 m (0.4×0.22 mi) scene. Not all martian landscapes have either feature, and there

Mars’ giant sweaters

A Piece of Mars: Sometimes in the floors of small craters, the wind blows in from several directions to produce odd polygon-shaped dunes that look like crochet (maybe Mars is making sweaters for its craters – it is, after all, a cold place). This “sweater” segment is 480×270 m (0.3×0.17 mi) in size (the “stitches”

Dunes carving up rock (3D)

A Piece of Mars: Get out your 3D blue/red glasses (or look here for a 2D version if you can’t find them). This is a 3.2×1.8 km (2×1.13 mi) scene showing dark dunes carving lanes 50-70 m (165-230 ft) deep into a stack of brighter sedimentary layers. Over time, the sand wears down the rock

Tortoise and hare

A Piece of Mars: There’s a lot of evidence for both fast and slow movement in this 480×270 m (0.3×0.17 mi) scene. The tortoise: The rippled surface at the top is high ground: the top of a dune. Wind pushes the ripples toward a steep sunlit slope, creating long thin, dark avalanches that slowly inch

Crater ejecta on old ripples

A Piece of Mars: Mars rarely does anything without drama. Long ago in this 0.96×0.54 km (0.6×0.34 mi) scene, large ripples formed and then, presumably, lithified (turned into rock). Some time after that, an impact formed the crater in the center, throwing debris into an ejecta blanket that covered the lithified ripples. That ejecta blanket