Martians Molded This Rock:

[link to wretchfossil.blogspot.tw]
Th above image was taken by Mastcam: Right (MAST_RIGHT) onboard NASA's Mars rover Curiosity on Sol 1450 (2016-09-04 01:26:01 UTC). Green arrows at upper right point to flat surfaces meeting in 90 degrees. Red arrows point to the internal structures of the object. If the object is a natural rock instead of an artificial rock, there should not be such differences in the surfaces of the object. Image source:
[link to mars.nasa.gov (secure)]