Curiosity photographed this curious stone to Mars. (top photo)
This photo taken by Curiosity on Mars on June 28, 2013 and posted on the official site on 28 July 2013. Contact: MastCam Left, SOL 318.
Click here to enlarge top photo.
This stone has a curious form:
It is shown here, official website:
ANOMALY ON MARS: PHOTOS: