Deposits of Sand: Ripples Versus Dunes - Dune Worlds: How Windblown Sand Shapes Planetary Landscapes - page 68

Fig. 5.27 Barchan scars on Mars, seen in HiRISE image
PSP_001882_1920 and noted by Gardin et al. (2012). Barchan dunes
are readily visible, as are ripples superposed on the dunes and
interdune floor. Bright arcuate streaks (arrowed) are interpreted as

cemented marks of former slip faces—the set of three in the center is
particularly indicative of progressive movement of a dune. Those arcs
are about 10 m across. Related features are seen on Earth at White
Sands, and Lencois Maranhenses. Image NASA/JPL/U.Arizona

Fig. 5.29 Buried snow layers, literally stumbled upon by the author,
on a parabolic dune at Great Sand Dunes National Park and Preserve
(Fig. 5.25 was taken on the other side of this dune, about two weeks
before this picture was taken). Much of the dune here is rock hard,
with moist sand frozen in place. The thickest snow layer here is about
4 cm thick. Note that it is the area where snow is present that has small
ripples on the surface, where perhaps the sand mobility has been
affected by moisture from the snow. Photo R. Lorenz

Fig. 5.28 A winter image from a timelapse camera (see Chap. 16 )
monitoring ripple migration and evolution at Great Sand Dunes
National Park and Preserve. After a snowfall, high winds caused
*2 m-wide ripple-like structures to form in the snow—mixed sand
and snow transport leads to curling layers visible at left. Image R.
Lorenz