NASA SP-2011-4234. This book presents the history of planetary protection by tracing the responses to the concerns on NASA's missions to the Moon, Mars, Venus, Jupiter, Saturn, and many smaller bodies of our solar system. The book relates the extensive efforts put forth by NASA to plan operations and prepare space vehicles that return exemplary science without contaminating the biospheres of other worlds or our own. To protect irreplaceable environments, NASA has committed to conducting space exploration in a manner that is protective of the bodies visited, as well as of our own planet.