The new 2020 Mars Rover will achieve its cost savings by using $200 million worth of flight-ready equipment left over from the Curiosity rover, said Jim Green, Director of the Planetary Science division within NASA. He spoke today at the Outer Planets Assessment Group meeting in Atlanta, GA.

Dr. Green did not specify which components this included, but John Grunsfeld, Director of NASA's overall science division said that the MMRTG (Multi-Mission Radioisotope Thermoelectric Generator) exists as a spare from the Curiosity rover when he announced the new mission in December.

The Jet Propulsion Laboratory also went through great effort to maintain updated schematics and detailed engineering and testing notes when constructing Curiosity so that they could readily build another model of the rover. While there will be differences in scientific instruments and the engineering required to support them, the entire landing system (including the sky crane and heat shield) and rover chassis can essentially be recreated without any additional engineering or research. This reduces overall technical risk for the mission, which allows for a smaller emergency reserve as part of its budget.

The 2020 Mars rover is designed to fit within a $1.5 billion budget, about $1 billion less than the Curiosity rover. NASA just announced an open call for applicants to the mission's Science Definition Team, which will clearly define the exact scientific goals of the project.