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
Human mission to Mars routine maintenance, and the harvesting of Martian resources for fuel, water, and building materials. NASA is still aiming for human missions to Mars in the 2030s, though Earth independence could take decades longer. In November 2015, Administrator Bolden of NASA reaffirmed the goal of sending humans to Mars. He laid out 2030 as the date of a crewed surface landing, and noted that planned 2020 Mars rover would support the human mission. Also discussed was the use of robotics to prepare an underground habitat for the arriving people. He noted the advantages of living underground on Mars, especially that it