The twin Mars exploration rover vehicles began in early April 2000 as the dream of a young Jet Propulsion Laboratory (JPL) engineer. After two disappointing failures of the Mars Climate Orbiter and the Mars Polar Lander, NASA and the JPL were interested in determining a new course to invigorate the Mars Program. The objective of this article is to set out a chronology of the events of this exciting project in order to provide the context and background for the other articles. Within a month of the approval, the project was also asked to develop not one but two rovers, both to be sent during the same launch period to two distinct sites on Mars. Their ultimate goal was to study the history of water on Mars, in line with the basic Mars Program goal "to follow the water"