A self-portrait by the Mars rover Curiosity on October 31, 2012. The mosaic is stitched from a set of 55 images taken by the Mars Hand Lens Imager at "Rocknest," the spot in Gale crater where the mission's first scoop sampling took place. Self-portraits such as this help NASA document the state of the rover and track changes, such as dust accumulation and wheel wear.Photograph: NASA
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