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 sample-return mission NASA and ESA called ExoMars, would launch in 2018 with unspecified missions to return the sample itself expected in the 2020–2022 time frame. The cancellation of the caching rover MAX-C and later NASA withdrawal from ExoMars, pushed back a sample-return mission to an undetermined date. Due to budget limitations the MAX-C mission, which was the first NASA-ESA mission leading to a MSR, was canceled in 2011 and the overall plan in 2012. The pull-out was described as "traumatic" for the science community. However, in April 2018, a letter of intent was signed by NASA and ESA that may provide a