Spirit Rover's Robotic Arm at Work. Twins Rovers sent by NASA to Mars are each fitted with a robotic arm and diverse instruments which allow them to act as geologists. Seen here is Spirit rover robotic arm (or "Instrument Deployment Device"). Robotic is at work about a rock dubbed Adirondack by reference to the New York range due to its mountain-shaped appearance. Scientists think that such rocks are "time capsules" of sort containing reminders of Martian past. Each rover is fitted too with a panoramic camera (Pancam) allowing him to see its environment, spectrometers for soil and minerals analysis, and with a microscopic imager which is providing close-up views of objects. An abrasion tool on the robotic arm permits grindings and access to rocks' layers. Rovers may overcome obstacles as tall as their predecessor the famous 1996 little Sojourner and they may travel as much as 100 yards a day. picture courtesy: NASA/JPL