Dune trails

There’s so much going on in this 0.75×0.75 km (0.47×0.47 mi) image. You’re looking at a broad dune migrating toward the upper right. It’s early summer, but this is close enough to the north pole that some winter ice lingers (pale blueish white), amid slumps that have shed down from the dune. The slumps probably

Where dune fields begin

This is the upwind edge of a dune field (825×625 m, 0.51×0.39 mi). Winds blow down a cliff (offscreen) from the lower right, blowing sand toward the upper left. Elongated dunes have formed parallel to the resultant wind direction, only avalanching into slip faces once enough sand has piled up (there are two slip faces

Varying wind directions

A Piece of Mars: This 0.5×0.4 km (0.31×0.25 mi) scene shows two dunes near the north pole. The shape of the dunes indicates two main winds: one blowing left to right (which makes slip faces on the right side, one of which still has some bright white ice on it), and a secondary wind blowing

Dunes with comet tails

A Piece of Mars: The north polar dunes in this 575×325 m (0.36×0.2 mi) scene are made of dark sand covered by bright winter frost (which will soon sublimate away, as this image was taken in late spring). To the right of the dunes extend pale yellow bumpy hills, making the dunes look like they

Dunes in a row

A Piece of Mars: Look at the alignment of the ~100 m dunes in this 713×750 m (0.44×0.47 mi) scene. How do dunes form in such straight lines? And why don’t they always do that? It’s likely that these dunes were once long ridges stretching from the lower right to upper left. The shape of

Mars’ giant bubble wrap

A Piece of Mars: This 0.7×0.5 km (0.43x.31 mi) scene shows Mars’ giant yellow bubble wrap, with each “bubble” about 100 m across (seriously, don’t you want to pop them?). These are actually a type of dune called a “dome dune”, and they’re about as small as this type of martian dune can get. Dome

Dunes fighting for survival

A Piece of Mars: Having a bad day? You’re in good company with these dunes in this 0.96×0.48 km (0.6×0.3 mi) scene. The gray barchanoid dunes are covered in ripples, as the wind valiantly tries to push the sand to the dune crests. But they are besieged by other processes at work. Dark scribbles show

Shades and textures

A Piece of Mars: This 480×270 m (0.3×0.17 mi) scene shows the contact between two very different terrains. On the left is a bright surface with polygonal cracks (characteristic of periglacial terrain – this is at a high latitude). On the right is a dark rippled sand sheet that superposes the polygonally-cracked surface. The long

Eroded dune

A Piece of Mars: Barchan dunes on Mars have a characteristic crescent shape, with a steep slope (“slip face”) on the inside of the sharpest curve (see examples like this, this, these, or this). This image (873×491 m, or 0.54×0.31 mi) shows an example of a dune that probably looked a bit like those other