Human analog missions are activities undertaken on Earth in various environments to simulate aspects of human missions to other worlds, including the Moon, asteroids, and Mars. These remote field tests are performed in locations that are identified based on their physical similarities to the extreme space environments of a target mission.[1] Such activities are undertaken to test hardware and operational concepts in relevant environments.
Obviously no analog can simulate all aspects of a human space mission here on Earth. That is why a wide array of analog activities are necessary, each testing only a few important concepts and/or hardware elements at a time.