Here is the reference information for the image posted above by goggog.
The information refers to a microscopic image captured of the surface of a large rock called "Block island" discovered by the rover 'Opportunity' in 2009. Scroll down to find the reference.
Look at the rock to the left. There is something that looks like the symbols carved in stone. This can only be cracks, but I think you better look at this. Maybe some of you try to sharpen the picture, I did not know at this completely ... Maybe some of you saw something similar before?