Curiosity (rover) arm operations were cleared to continue, but drilling remained suspended indefinitely. The "Curiosity" team continued to perform diagnostics and testing on the drill mechanism throughout 2017. "Curiosity" has an advanced payload of scientific equipment on Mars. It is the fourth NASA unmanned surface rover sent to Mars since 1996. Previous successful Mars rovers are "Sojourner" from the Mars Pathfinder mission (1997), and "Spirit" (2004–2010) and "Opportunity" (2004–present) rovers from the Mars Exploration Rover mission. "Curiosity" is long by wide by in height, larger than Mars Exploration Rovers, which are long and have a mass of including of scientific instruments. In
Mars sample-return mission request of NASA and the NSF, declared a MSR campaign its highest priority Flagship Mission for that period. In particular, it endorsed the proposed Mars Astrobiology Explorer-Cacher (MAX-C) mission in a "descoped" (less ambitious) form, although this mission plan was officially cancelled in April 2011. In September 2012, the United States' Mars Program Planning Group endorsed a sample-return after evaluating long-term Mars' plans. The key mission requirement for the planned Mars 2020 rover is that it must help prepare NASA for its MSR campaign. which is needed before any crewed mission takes place. Such effort would require three additional vehicles: