Mars Exploration Rover Vehicles
The Mars Exploration Rovers are six-wheeled robotic vehicles that are exploring the surface of Mars. The rovers, powered by solar panels, are robotic "field geologists" that are examining Martian rocks and soil for signs of the presence of liquid water in Mars' past. The top speed of the vehicles, which are about the size of a golf cart, is five centimeters (2 inches) per second. Allowing for rocky ground and factoring in caution while negotiating rough terrain, the rovers are expected to travel up to 40 meters (130 feet) each Martian day. The vehicles are designed to survive for 90 Martian days, traveling a total of about one kilometer (0.6 miles) during that time.
Each rover has nine cameras. Six of the cameras are for navigation and hazard avoidance, one is a microscopic imager for taking detailed close-up views of rocks, and a pair that are mounted atop a mast roughly the height of a human (about 1.4 meters, or five feet, above the ground) shoot stereoscopic panoramas of the rover's surroundings. The vehicle has a mass of 170 kilograms, so it weighs 375 pounds on Earth but just 140 pounds in the weaker Martian gravity.
The rover has a robotic arm carrying several instruments that it is using to examine rocks and soil. The Mössbauer Spectrometer analyzes the mineral content of iron-bearing soil and rocks. The Alpha Particle X-Ray Spectrometer (APXS) determines the abundances of various elements in rock and soil samples. A Rock Abrasion Tool (RAT) mounted on the arm grinds away the outer, weathered surface of rocks to allow the other instruments to examine "fresh" material within. The microscopic imager camera is also mounted on the arm.
Magnets mounted on the rover's body collect magnetic dust particles from the air and ground up minerals scraped from rocks by the RAT, helping to characterize the iron content of those materials. The vehicle also carries a Miniature Thermal Emission Spectrometer (Mini-TES) that is helping scientists identify rocks and soil that warrant a closer look, determine the processes that formed specific rocks, and gather data on temperature profiles of the Martian atmosphere (when pointed skyward).