NASA's Mars Science Laboratory spacecraft has been fully stacked for flight in this photograph from inside the Payload Hazardous Servicing Facility at NASA Kennedy Space Center, Fla., in October 2011.

The spacecraft, including the Mars rover Curiosity, has been prepared for launch during the period Nov. 25 to Dec. 18, 2011. In a prime mission lasting one Martian year -- nearly two Earth years -- after landing, researchers will use the rover's tools to study whether the landing region has had environmental conditions favorable for supporting microbial life.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for NASA's Science Mission Directorate in Washington. Launch management is the responsibility of NASA's Launch Services Program at the Kennedy Space Center in Florida. The Atlas V launch service is provided by United Launch Alliance, Denver, Colo.