Mars Rovers Mark 2-Year Anniversary Published Dec. 4, 2006 By Propulsion Directorate AFRL/PR WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- AFRL-developed technology plays a key role in the remarkable longevity of the Mars rovers, Spirit and Opportunity, which recently marked their 2-year anniversary on the Red Planet. Spirit landed on Mars in January 2004, and Opportunity arrived 3 weeks later. Though scientists expected both rovers to operate on Mars' surface for ~90 days, the rovers exceeded that expectation by a factor >8. AFRL was instrumental in the development of the lithium-ion battery technology that helps to power the rovers on the Martian surface. These lithium-ion batteries keep the rovers "alive" at night and provide additional power during intensive daytime operations. AFRL planned and managed the Lithium-Ion Battery Research and Development program, in which scientists established the cell chemistry and cell design for these batteries. AFRL's contribution to the battery development effort was possible with cooperation and funding from both the Army and the National Aeronautics and Space Administration's Jet Propulsion Laboratory.