Like any vehicle, Curiosity's wheels have to roll over whatever lies in its path. Sadly, that path isn't always smooth: Now, the rover has a chunk of rock wedged in one of the grooves of its wheels.
According to New Scientist, NASA scientists aren't too concerned about the stone. They don't expect it to affect the performance of the Rover, and while plans have apparently been discussed to shake the rock free, "it is better to let this fall off naturally," according to NASA scientists Chris Roumeliotis.
That might be because Curiosity's wheels are already in a pretty bad way. Last year, it came to light that the rover's wheels are already in tatters — though one of the best solutions to prolong their life was said to be driving over smoother terrain. Clearly that hasn't quite been going to plan. [New Scientist]