October 6, 2014

Almost a dune

A Piece of Mars: This field of 2 m wide sand ripples has a dark splotch in the middle (the scene is 300×225 m or 984×738 ft). The splotch is the peak of a low hill that straddles the classification […]
September 30, 2014

Lumpy bumpy dunes

A piece of Mars: These funny shaped dunes were formed by winds blowing from two directions – one from the top of the frame and one from the upper right. Both winds make steep slopes (slip faces) on the downwind […]
September 22, 2014

Changing winds

A piece of Mars: There are two sets of ripples here: tan ones and gray ones, each oriented to a different wind (scene is 300×225 m, or 984×738 ft). The gray ones sit on top of the tan ones, so […]
September 15, 2014

Missing bedrock

A piece of Mars: Wind flow on Mars can be quite dramatic. Here, a single wind-sculpted hill stands 1.5 km (0.93 mi) wide and 600 m (1970 ft) high (color shows elevation). That sounds big, but vastly larger is the […]
September 8, 2014

Martian waves

A piece of Mars: The swirly candy stripes in these big dark dunes are layers inside that have been made visible by wind erosion (the scene is 1.5×0.9 km, or 0.93×0.56 mi). It’s rare to see the inside structure of […]
September 3, 2014

Holes around rocks

A piece of Mars: This scene (509×382 m, or 1670×1253 ft), aside from showing some lovely rippled dunes, has many car-sized boulders in it. Some are surrounded by ditches in the sand, like little moats. Why? The sand is blown […]
August 25, 2014

Which wind came first?

A piece of Mars: This scene (3.9×2.5 km or 2.4×1.6 mi) shows a surface carved by two different winds: one blowing from the right and one blowing from the bottom right. They’ve formed overlapping sets of streamlined rocks called yardangs. […]
August 18, 2014

How the wind turns

A piece of Mars: The two shadowed hills in the upper part of this frame (497×373 m or 1631×1224 ft across) rest on a flat plain covered in large ripples. On the plain the ripples are aligned north-south, formed perpendicular […]
August 14, 2014

Wind within vs. wind without

A piece of Mars: Dunes outside the crater are straight but the ones inside the crater look like a spiderweb. Why? This image shows just how much the topography of a crater wall can affect the wind, which produces a […]