September 18, 2015

A wind-levelled surface

A Piece of Mars: In this 676×380 m (0.42×0.24 mi) scene, the high-standing hills here were all carved by sandblasting, by a wind that probably blew from right to left. Ripples in the valleys show that this erosion is still […]
September 7, 2015

Sand sheets and ripples

A piece of Mars: Not all sand piles up into big dunes. If the grains are the wrong grain size (too fine or too coarse), then it might just form sand sheets with ripples on top, like it does here, […]
August 31, 2015

Layered winds

A piece of Mars: On the left is high ground, covered with dunes (or maybe they’re ripples) running from upper left to lower right. On the right is low ground, covered in deeply eroded dunes (ripples?) running almost from left […]
August 26, 2015

Stealth bomber dunes

A piece of Mars: These dunes look strangely triangular, a little bit like a flock of stealth bombers. Why? They’re two-faced barchans. Each flat face is an avalanche slope that faces downwind, formed by one of two distinct wind patterns […]
July 31, 2015

What is burying what?

A piece of Mars: There’s an egg-shaped plateau here (the whole scene is 480×270 m or 525×295 yd across, the “egg” is ~100 m long). It’s partly covered by dunes that have extended across it. Or were the dunes there […]
July 27, 2015

Dust devils and wind scours on ripples on dunes

A piece of Mars: So much wind. There are dark swirly tracks of dust devils that have passed by, ripples covering dunes, wind scours around rocks, and of course dunes. Dune crests have a different color than other regions: are […]
July 6, 2015

Frosty dunes

A piece of Mars: In this image (0.96×0.54 km or 0.6×0.33 mi), it’s late winter and the sun is barely above the horizon here near the north pole. The dunes are covered in winter frost, most of which is CO2 […]
June 1, 2015

Small dunes on Mars

A piece of Mars: These dunes are some of the smallest on Mars. The smallest in this frame is ~150 m long (492 ft). But the smallest Earth dunes are ~20 m across. Why are they so much bigger on […]
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 […]