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
Crewed Mars rover An early version of the SEV rover was tested in 2008 by NASA in the desert. The SEV for space or roving missions was designed to support two humans for 14-days, and would include a toilet, sleeping logistics, and one version has suitports to support EVAs. Another concept is a windows that allow looking at objects very close to the front of the rover but on surface (down and to the front). In the 1960s, the post-Mariner 4 design for a Mars Excursion Module, by Marshall Space Flight Center, including a cargo version carrying a pressurized Mobile Laboratory for Mars,