Last updated on March 13, 2014 at 18:18 EDT The Answer is in the
Crests and Troughs 760 of 942  The Answer is in the Crests and
Troughs  December 19, 2004 This microscopic image taken by the
Mars Exploration Rover Spirit shows the troughs between the
waves of windblown soil that characterize the surface of Gusev
Crater, Mars. The fine-grained soil in the troughs, combined
with the coarse grains observed in a similar microscopic image
taken of the waves' crests, indicate that the waves are geologic
features known as ripples, and not dunes. Dunes contain a more
uniform distribution of material. This information helps
scientists better understand the winds that shape the landscape
of Mars. The image was taken on the 41st martian day, or sol, of
the rover's mission by its microscopic imager. The observed area
is 3 centimeters (1.2 inches) across.