I posted this image a few days ago. I read the site where it appears every day, but this is the first time I remember being totally stumped by an image.
It’s a photo of a Martian plain, taken by the HiRISE camera on the Mars Reconnaisance Orbiter. It appeared on the Astronomy Picture of the Day site on October 21, 2009. The black trails are thought to be the underlying bedrock after surface dust has been disturbed by dust devils.
Surprised?
cleve callison’s blog 
It’s really scary to contemplate how that bar code got on Mars! Wal-Mart’s reach exceeds our imagination.