Dunes

All pictures on this page are about 2 miles in width.

Sand dunes are very common on Mars.  Sand dunes are made of sand-sized particles, which are much larger than the dust which covers most surfaces and is present in the atmosphere.  To make dunes the sand travels around by a  process called "saltation."  This method of travel involves a series of rolls, bounces, and jumps.
In the image below, intersecting sand dunes form cells that are the size of lots for houses--between 1/6 to 1/2 acre each. 

Dark dunes are formed of small sand-sized bits of a common rock known as "basalt."  Basalt, a volcanic rock, is common on  Earth, the Moon, Venus,  Mars, and even some asteroids.

Cresent-shaped dunes are called barchans.  They are formed from steady winds of medium strength.  They indicate wind direction.  The convex side faces the wind, so in the picture below the wind is blowing from right to left.

MOC S14-00717

Below are super large, dark dunes with a bit of frost.

Below are three buttes and part of a mesa.  At some time in the past the whole was covered with a  light colored deposit.  That deposit has since worn away except for the light areas that make up the buttes and mesa.  These forms are similar in size and shape to the landscape in Monument Valley.

MOC S14-00717

In the mesas below there is a great deal of dust  causing a softer appearance to the whole landscape.  Some dark streaks are apparent.  They are caused by material sliding down in an avalanche type of movement.  They seem to occur only in the warmest places--where the temperature has risen to above the melting point of water.

For more images click here.

Revised January 2007