Photography by Curiosity in Gale Crater:
Nice wider view
Composition and other information
Sand ripple on patch of ground named Rocknest. I don't know the exact scale, but it looks to be about 30-60 cm wide. The small blobs of texture seem to be pebbles coated in dust.
After a scoop from near the ripple.
The ripple above extends into the foreground of this navigation camera photo, looking to the rim of Gale Crater.
Robot wheel impression across the ridge. The body of the ripple appears to be very fine grained, more like flour than sand.
Top of wheel print above, but with different sun angle (time of sol). Original.
Closeup of part of this wheel-print. Original. The straight horizontal bands are impressions of the wheel surface (see wheel image below).
Closer view at edge of imprint:
"The largest grains ... are about 0.04 to 0.08 inches (1 to 2 millimeters) in size. The bulk of the sand in the ripple is smaller, in the range below 0.002 to 0.008 inches (50 to 200 microns).
Wheels of Curiosity that made the impressions. Each is about 40 cm wide. Notice the fine linear texture of the left wheel in the highlight. This pattern is seen as horizontal bands in the dust (two images above, top).