Curiosity has photographed these strange shapes on Mars December 2, 2013
I circled in black these two strange shapes, and I enlarged.
The photo that interests us here: it was taken Dec. 2, 2013, and posted on the official website December 2, 2013. Coordinates are: Right NavCam B, SOL 470.
The photo is listed on the official website here:
ANOMALY ON MARS AND BEYOND: PHOTOS: