Even on Mars, the unstoppable force inevitably meets the immovable object. The BBC is reporting that the Curiousity Rover has come up against a geographic block on the surface of Mars: a meter-high sand dune.
From the BBC...
"The sand bank is currently blocking the robot's path into a small valley and a route with fewer of the sharp rocks that lately have been making big dents in the vehicle's aluminum wheels.
US space agency engineers will take no risks, however. The rover will be commanded initially to climb only part way up the dune to see how it behaves"
Engineers are proceeding cautiously because a similar dune was almost the end of the Opportunity Rover, which became mired in a loose sand pit full of debris that quickly earned the nickname "Purgatory Dune."