A photograph taken by the Curiosity Mars Rover shows an abandoned mining crawler or at least a part of the crawler likely used to take Mars materials.
The same photo also shows what looks like a strange human-like figure dressed in a black suit on top of the ridge apparently inspecting something, but of course it just could be an incorrect perception of a natural mars object.
About the mining crawler, although our brains are not used to seeing alien technology, this object is clearly a machine or part of a machine previously used by an unknown intelligent specie.
Link image: http://gigapan.com/galleries/13375/gigapans/205531