[RedskinRat]

NASA’s Curiosity rover may not look like an urban menace, but the robot explorer will in fact be steadily tagging the Martian surface as it trundles, leaving a name-check of the Jet Propulsion Laboratory back home. The clandestine graffiti is thanks to part of the rover’s visual odometry system, John Graham-Cumming points out, which tracks the marks left by a series of asymmetrically arranged holes in the wheels. The position of those holes, however, isn’t random: in fact, it’s Morse Code.