No. 37: Jan-Feb 1985
The preceding, almost-Lowellian vision of a watery Mars is quite different from what the Mariner and Viking spacecraft tell us about the planet's present condition. Wind rather than water is now the main erosional force. The sand dunes and drifts, the wind-shadows behind rocks, and the sand-blasted surfaces all attest to the desertification of Mars. Ronald Greeley, of Arizona State University, and his colleagues have simulated Martian winds in a special wind tunnel at NASA's Ames Research Center. Using spacecraft-measured wind velocities and patterns, they tried to duplicate the Martian erosional environment. The results were a surprise. They implied that the Martian surface should be worn down by wind-driven sand and dust at rates up to 2 centimeters per century. But at that rate, the Martian craters, which are estimated to be hundreds of millions of years old, would have been worn level long ago. The researchers are now wondering what is wrong with their simulation. They venture that the Martian sand may not be "normal," or perhaps the eroding particles do not travel as fast as they figured.
(Anonymous; "The Windblown Planet Mars," Sky and Telescope, 68:507, 1984.)
Comment. Another interpretation is that Mars has not been desert-like for as long as presently believed.
Reference. The subject of Martian crater obliteration is discussed further in AME20 in our Catalog: The Moon and the Planets. Ordering information here.