This observation shows a part of a central mound in an impact crater in Arabia Terra. At low resolution, the mound is relatively smooth and featureless, although elsewhere in the mound a Mars Orbiter Camera (MOC) image shows fine layers.

The mound is broad, filling much of the crater, although it now appears to be eroding. Images like this can be used to explore the nature of the deposit, and provide clues about how it formed. At high resolution the material still appears relatively uniform and featureless, without boulders or obvious fine layers. This indicates a relatively weak, fine-grained material.

The large, elongated features in the image are yardangs. These are characteristic of aeolian (wind) erosion. They form roughly parallel with the direction of the prevailing wind, and the streamlined shape (often compared with the hull of a boat) is created by persistent flow from this direction.

Yardangs on Earth often form from relatively unconsolidated material, supporting the inference made from the appearance of the deposit.

Written by: Colin Dundas   (28 April 2010)