An artist's concept shows a NASA Mars exploration rover on the surface of Mars. The twin rovers Spirit and Opportunity were launched in 2003 and arrived at sites on Mars in January 2004.
This composite image provided by NASA shows before-and-after images taken by the Opportunity rover on Mars of a patch of ground taken on Dec. 26, 2013, showing the "Pinnacle Island" rock.
A photo composed of nearly 900 images taken by the rover Curiosity shows a section of Gale Crater near the equator of Mars. The rovers are continuing to work through the U.S. government shutdown.