Sand dunes have been found in many places on Mars.
 The presence of dunes shows that the planet has an atmosphere with wind, for dunes require wind to pile up the sand.
 Most dunes on Mars are black because of the weathering of the volcanic rock basalt.
  Black sand can be found on Earth on Hawaii and on some tropical South Pacific islands.

Sand is common on Mars due to the old age of the surface that has allowed rocks to erode into sand.
Dunes on Mars have been observed to move many meters.

Some dunes move along.
 In this process, sand moves up the windward side and then falls down the leeward side of the dune, thus caused the dune to go toward the leeward side (or slip face).

When images are enlarged, some dunes on Mars display ripples on their surfaces.
  These are caused by sand grains rolling and bouncing up the windward surface of a dune.
 The bouncing grains tend to land on the windward side of each ripple.
 The grains do not bounce very high so it does not take much to stop them.
Sand dunes have been found in many places on Mars.  The presence of dunes shows that the planet has an atmosphere with wind, for dunes require wind to pile up the sand.  Most dunes on Mars are black because of the weathering of the volcanic rock basalt.   Black sand can be found on Earth on Hawaii and on some tropical South Pacific islands.
Sand is common on Mars due to the old age of the surface that has allowed rocks to erode into sand. Dunes on Mars have been observed to move many meters.
Some dunes move along.  In this process, sand moves up the windward side and then falls down the leeward side of the dune, thus caused the dune to go toward the leeward side (or slip face).
When images are enlarged, some dunes on Mars display ripples on their surfaces.   These are caused by sand grains rolling and bouncing up the windward surface of a dune.  The bouncing grains tend to land on the windward side of each ripple.  The grains do not bounce very high so it does not take much to stop them.
Ismenius Lacus quadrangle