No bones about it! Seen by Mars rover Curiosity using its MastCam, this Mars rock may look like a femur thigh bone. Mission science team members think its shape is likely sculpted by erosion, either wind or water….. [More at link]
NASA description: This image was taken by Mastcam: Right (MAST_RIGHT) onboard NASA’s Mars rover Curiosity on Sol 719 (2014-08-14 21:49:28 UTC).
Sol 719 raw images (from all cameras), and Curiosity’s latest location map.