As Curiosity awakened on Mars after its long journey, this is the first image taken by the Navigation cameras, showing the rover's now-upright mast in the center, and the arm's shadow at left. The arm itself can be seen in the foreground.
The navigation camera on the mast is used to help find the sun -- information that is needed for locating, and communicating, with Earth. After the camera pointed at the sun, it the turned in the opposite direction to view it's shadow, helping to confirm the sun's location, and thus the positioning of the rover itself.
See the full-resolution 1024 by 1024 pixels image here.
Curiosity's first high-res images (pictures)
by CNET News.com | August 8, 2012, 2:00pm PDT | Image 2 of 4