Martian Racetracks

Wind-sculpted flats on Mars near Olympus Mons. The banner image highlights the fine rows as they curve to the left like a racetrack turn. In the very large original image, this segment is middle left of the full image above.
Credit: ESA/Mars Express

These images of ‘yardangs’, features sculpted by wind-blown sand seen here near Olympus Mons on Mars, were obtained by the High Resolution Stereo Camera (HRSC) on board the ESA Mars Express spacecraft.

This image was taken during orbit 143 with a resolution of 20 meters per pixel. This scene shows a structure south of Olympus Mons at 6° N latitude and 220° E longitude, which was probably formed by the action of the wind.

Loose sand fragments were transported by wind, and impacted on the bedrock, slowly removing parts of the surface, like a sand-blaster.

If the winds blow in the same direction for a long enough period, ‘wind-lanes’, as shown in the picture, can occur. On Earth, the remnants of these features which have not been eroded away are called ‘yardangs’.

Where the surface consists of more resistant material, the force of the wind may not be strong enough to cause this sand-blasting. This might be the reason for the three flat regions (the first in the foreground on the left, and the others top right), which measure about 17 by 9 kilometers.

Martian terrain
Layered martian terrain in painting by Bill Hartmann (left), orbital image from Mars Orbital Camera (right).
Copyright William K. Hartmann

The color image was created from the nadir (vertical) and three colour channels; the perspective view is created from the nadir and stereo channels of the camera. The original resolution of the image is reduced for use on the internet.

Notable in the banner image particularly is an apparent left turn like a swirl in the fine structure of the middle left from the full Mars Express image. While there is no obstacle that might lead to such windward turns in the erosion pattern, the scale of nearly ten by ten miles suggest a much larger, but shallow terrace.


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