Landers and rovers bring our point of view down to ground level. They have performed on-site experiments and given us crystal-clear views of the Martian landscape.
Pathfinder came equipped with an imager and meteorology sensors and delivered the first rover to the Mars.
Spirit was sent to the floor of a 140-kilometer (90-mile) wide crater named Gusev.
Opportunity was sent to Meridiani Planum, a smooth area near the Martian equator.
Curiosity was sent to Gale Crater, which is 150 kilometers (about 90 miles) in diameter and contains a large central mound.
To search for clues to the history of water on Mars, NASA sent twin "robot geologists" to the Red Planet. The two rovers landed in 2004 and continued to operate long past their original 90-day mission plan.
This rock was used in laboratory testing of the Rock Abrasion Tool (RAT), an instrument on the rover's robotic arm. The RAT grinds a small hole in a rock to obtain a fresh, unweathered, dust-free surface for analysis and imaging.
This shale from Ohio has some physical properties in common with Martian rocks analyzed by the Opportunity rover. The grinding on this sample took four hours to produce a hole about 5 millimeters (0.2 inch) deep.
RATted Cleveland Shale lent by Honeybee Robotics