The Mars Exploration Rover (MER) mission cost $1.08 billion. Of that amount, $744 million was spent on spacecraft development and launch; $335.8 million was spent on 15 years of mission operations.
MER accounted for 0.0017% of all spending by the United States during the 20-year period covering the rovers' development and operations. The final fiscal year of funding for MER was 2019.
Mars Exploration Rover costs per fiscal year. The twin rovers launched in 2003 and began Mars surface operations after their landings in January of 2004. After their prime mission completion 90 days later, both rovers began extended operations. Spirit continued until May of 2011. Opportunity ended in 2018. Source: Planetary Science Budget Dataset, compiled by Casey Dreier for The Planetary Society (accessible on Google Sheets or downloadable as an Excel file).
|Spacecraft Development & Launch (Delta II)||$744 million|
|Mission Operations (15 years)||$335.8 million|
Raw data available in Planetary Exploration Budget Dataset.
The twin Mars Exploration Rovers (MER), Spirit and Opportunity, were robot field geologists. They confirmed liquid water once flowed across the Martian surface. Both long outlasted their planned 90-day lifetimes. Following their landings on 3 and 24 January 2004, Spirit drove 7.73 kilometers and worked for 2210 sols (Martian days), until 22 March 2010. Opportunity drove 45.16 kilometers and worked for at least 5111 sols; the rover stopped responding on 10 June 2018, and the mission was declared over on 13 February 2019.