September 5, 2016

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 […]
August 8, 2016

Fossil dunes

A Piece of Mars: This 1.92×1.08 km (1.19x 0.67 mi) scene shows eroded ridges that are, in fact, lithified dunes. They are so old that you might not recognize them as dunes without more context. This doesn’t happen much on […]
August 1, 2016

Dunes not in the global dune database

A Piece of Mars: Ten years ago I participated in a global survey of martian dunes. But we missed a few dune fields, like these beauties. They’re small, low, and in rugged terrain, which made them difficult to spot in […]
June 6, 2016

Itty bitty changes: places where the wind barely moves sand

A Piece of Mars: Not all dunes on Mars are moving at a measurable pace. This 0.96×0.45 km (0.6×0.28 mi) scene looks a lot like one I posted 3 years ago called Martian Sports. This image shows the same dunes […]
May 16, 2016

Wind shadow

A Piece of Mars: There’s a dune field migrating past a 230 m (755 ft) diameter crater, creating a 1.6 km (1 mi) long “shadow” that’s empty of dunes. Why? The rim of the crater pokes up just enough to […]
March 28, 2016

Three types of windblown piles of stuff

A Piece of Mars: The wind blows different sorts of sediment in different ways. Ultimately they pile up because some oddity in nature makes one spot accumulate more sediment than other spots, allowing that windblown pile of stuff to grow. […]
March 16, 2016

Dune shadows

A Piece of Mars: Normally I post in color, but sometimes you need to back out to the grayscale images to see the big awesome things. This scene is 4.6×2.6 km (2.8×1.6 mi); the conical hill is 1.4 km (0.89 […]
January 12, 2016

Springtime for sand dunes and polar ice

A Piece of Mars: This 480×270 m (0.3×0.17 mi) scene shows a dark dune peeking out from under its cover of winter frost. In this picture it’s late spring, but still cold up at this latitude – it’s as far […]
December 21, 2015

Curiosity about sand dunes (part 2/2)

Today is December 21, 2015 (northern winter and southern summer solstice on Earth). On Mars it is Ls = 84º, Mars Year 33 (about 12 sols from northern summer and southern winter solstice on Mars). It is sol 1200 of […]