Spirit and Opportunity are the two rovers involved in the NASA mission called Mars Exploration Rover or MER. The two robotic vehicles have been exploring Mars since 2003.
The purpose of this mission is to find proof of life on the surface of Mars by searching and describing varied rocks and soils. MER is included in the Mars Exploration Program developed by NASA, following other three successful landers: 1976 Viking program lander and 1997 Mars Pathfinder probe.
The primary mission on the Martian surface cost 820 million USD and due to the rovers functionality over the initial 90 sol, their activity was extended to five more missions. The last of the five extensions was conferred in October 2007 and it ended in 2009. All the five extensions reached a cost of about 124 million USD.
In July 2007 there was a moment of uncertainty for the fourth mission, as the dust storms around Mars did not permit the sunlight to get through and fuel the craft with solar energy. Before any damage was caused, the storms lifted and the crafts got the solar energy they needed.
In 2009, Spirit got stuck in the Martian soft soil during its fifth extension of the mission. Despite the nine months effort to find solutions to get it back on track, the NASA officials had to announce in January 2010 that Spirit would continue its activity as a stationary platform for science research. This would give extra advantage in supporting the scientistsâ€™ research.
Due to the important contribution for space science that the two rovers brought, there were two asteroids named after them: 39382 Opportunity and 37452 Spirit. The rovers were operated by Jet Propulsion Laboratory, the same entity that designed and built them. It is JPL which also manages the project for NASA.