A Steep North Polar Scarp On Mars
This very steep (more than 60 degrees) scarp shows mass wasting activity every year in the early northern spring, when it is first illuminated after the period of winter darkness.
This observation was an attempt to image in late northern winter, in spite of poor illumination. The solar incidence angle is 91.3 degrees, meaning that the Sun is just below the horizon and there was no direct lighting when this image was acquired.
However, the atmosphere scatters light to create some diffuse lighting, and the surface is very bright from winter frost deposition, so a useful image of the surface was obtained. The image reveals relatively dark streaks down the steep slope, so mass wasting activity has already started. There is some direct illumination here close to noontime at this time of year, which may be sufficient to initiate some activity.
