Mars rover to regain contact. Mars 2, Mars 3 were physically tethered probes; "Sojourner" was dependent on the Mars Pathfinder base station for communication with Earth; MER-A & B and "Curiosity" were on their own. Of these "Curiosity" is still active, and "Spirit", "Opportunity" and "Sojourner" completed their missions before losing contact. Seven rovers have been dispatched to Mars: "Examples Landed instrumentation" (Rovers) Mars rovers in development include: One experimental design, not proposed for any actual mission, is: NASA distinguishes between "mission" objectives and "science" objectives. Mission objectives are related to progress in space technology and development processes. Science objectives are met
Mars Exploration Rover sequence on airbag inflation and backshell RAD rocket firing. Airbags used in the Mars Exploration Rover mission are the same type that Mars Pathfinder used in 1997. They had to be strong enough to cushion the spacecraft if it landed on rocks or rough terrain and allow it to bounce across Mars' surface at highway speeds (about 100 km/h) after landing. The airbags had to be inflated seconds before touchdown and deflated once safely on the ground. The airbags were made of Vectran, like those on Pathfinder. Vectran has almost twice the strength of other synthetic materials, such as Kevlar,