Long Shadows at Ariadnes Colles (PSP_009161_1450)

Ariadnes Colles is a labyrinth-like cluster of hills, mesas, and knobs located near Terra Cimmeria, in the Southern Highlands of Mars.

This image, which covers a portion of that labyrinth, was acquired only a few sols (Martian days) away from winter solstice. Winter solstice occurs in the shortest sol of the year, when the Sun travels the lowest in the Martian sky, making shadows appear very long. These conditions are ideal to analyze modest relief features, that would pass unnoticed when illuminated from above but are highlighted when illuminated from the side.

This subimage of the enhanced-color combination shows one of the hills in detail.

The hill appears criss-crossed by long fractures, most of them made apparent by the shadows they cast. The shadows indicate that the fractures "stick out" from their surroundings, and hence that they are more resistant to erosion. In terrestrial environments this occurs when fluids flow along the fractures, leaving behind cementing minerals or when fractures are filled by igneous materials.

More at hirise.lpl.arizona.edu