Added on March 1, 2017: More Artificial Blocks at Same Location
This image was taken by Mastcam: Right (MAST_RIGHT) onboard NASA’s Mars rover Curiosity on Sol 1434 (2016-08-18 13:16:17 UTC) at the same place as the two photos above.
Red arrows point to broken artificial blocks. They possess flat surfaces that meet in 90 degrees. Green arrows point to flat surfaces with nearly straight edges. Image source: mars.nasa.gov/msl/multimedia/raw/?rawid=1434MR00708801707…