Layers of bedrock etched by wind to form sharp, elongated ridges known
to geomorphologists as yardangs are commonplace in the southern
Elysium Planitia/southern Amazonis region of Mars. The ridges shown in
this “3-D” composite of two overlapping Mars Global Surveyor (MGS)
Mars Orbiter Camera (MOC) images occur in the eastern Aeolis region of
southern Elysium Planitia near 2.3°S, 206.8°W. To view the
picture in stereo, you need red-blue “3-D” glasses (red filter over
the left eye, blue over the right).

For wind to erode bedrock into the patterns seen here, the rock
usually must consist of something that is fine-grained and of nearly
uniform grain size, such as sand. It must also be relatively easy to
erode. For decades, most Mars researchers have interpreted these
materials to be eroded deposits of volcanic ash. Nothing in the new
picture shown here can support nor refute this earlier
speculation. The entire area is mantled by light-toned dust. Small
landslides within this thin dust layer form dark streaks on some of
the steeper slopes in this picture (for more examples and explanations
for these streaks, see previous web pages listed below).

The stereo (3-D) picture was compiled using an off-nadir view taken by
the MOC during the Aerobrake-1 subphase of the mission in January 1998
with a nadir (straight-down-looking) view acquired in October 2000.
The total area shown is about 6.7 kilometers (4.2 miles) wide by 2.5
kilometers (1.5 miles) high and is illuminated by sunlight from the
upper right. The relief in the stereo image is quite exaggerated: the
ridges are between about 50 and 100 meters (about 165-330 feet) high.
North is toward the lower right.