High-Resolution View of a Cross-Section through a Martian Ripple - Sol 58 (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunar Explorer Italia - Italian Planetary Foundation)

Caption NASA:"This image shows the wall of a "scuffmark" made by the NASA - MER Curiosity in a Windblown Ripple of Martian Sand, by using one of its wheels. The upper half of the image shows a small portion of the side wall of the scuff and a little bit of the floor of the scuff (bottom of this image). The prominent depression with raised rims at the bottom center of the image was formed by one of the treads on Curiosity's front right wheel.
The largest Grains of Sand in this image are about 0,04 to 0,08" (such as about 1 to 2 millimeters) in size. Those large Grains were on top of the Windblown Ripple and fell down to this location when the scuff was made. The bulk of the Sand in the Ripple is smaller, in the range below 0,002 to 0,008" (i.e.: 50 to 200 microns). The full scuffmark is about 20" (such as approx. 50 centimeters) wide which is, by the way, the same width of Curiosity's wheel.

This image from the Mars Hand Lens Imager (MAHLI) is the product of merging 8 (eight) images acquired at 8 (eight) slightly different focus settings to bring out details on the wall, slopes, and floor of the wheel scuff. The merge was performed onboard the MAHLI instrument to reduce downlinked data volume.
The image was acquired by MAHLI with the lens about 4,7" (approx. 12 centimeters) from the target. The pixel scale is about 0,002" (such as approx. 50 microns) per pixel. The image covers an area, roughly 3 by 2" (such as about 8 by 6 centimeters). The image was obtained on October, 4, 2012 - such as the 58th Sol, or Martian Day, of operations of the MER Curiosity on the Surface of Gale Crater".