mass wasting

March 1, 2018

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 […]
July 25, 2017

Cross-strata or not?

A Piece of Mars: Sand dunes are one of the few sedimentary phenomena that leave behind layers that aren’t horizontal. They tend to have a characteristic lean to them (and we call them cross-strata). So when I see something that […]
February 21, 2017

Who wins in the fight of wind vs. ice?

A Piece of Mars: This is the crest of one of the largest dunes on Mars (0.5×0.5 km or 0.31×0.31 mi). The wind mostly blows from the right, slowly pushing sand up the windward slope. But frost accumulates on (and […]
September 19, 2016

Light and dark

A Piece of Mars: This 0.96×0.54 km (0.6×0.34 mi) late winter scene is a study in contrast. The dark top half is uniformly rippled. This is the shady surface of the main windward side of one of Mars’ biggest dunes, […]
July 5, 2016

Landslides unlike any on Earth

A Piece of Mars: Click on this 0.96×0.54 km (0.6×0.33 mi) scene to see it in detail. Many thin, narrow landslides have formed on these dust-coated hills. As far as I’m aware, there’s nothing like this on Earth. Inside the […]
April 19, 2016

Stripes by wind and gravity

A Piece of Mars: This scene (800×450 m or 0.5×0.28 mi) is a steep slope, with high rocky outcrops on the upper right and both gullies and ripples heading downslope to the lower left. The wider, brighter stripes are gullies […]
November 24, 2015

Too steep for ripples

A piece of Mars: This 480×270 m (0.3×0.17 mi) area is a steep slope that plunges down to the upper left. A pile of dark sand, covered by brighter tan dust, clings to the hillside. Usually the martian wind blows […]
May 25, 2015

The looming dune

A piece of Mars: this 0.96×0.54 km (0.6×0.33 mi) scene shows a large, rippled dune that is slowly marching towards the upper right. The smooth striped band running from upper left to lower right is the slip face, where sand […]