Preventing the forward contamination of Mars: concerns, questions, and required actions

New data are now forthcoming about the nature of the Martian environment and its potential to harbor Earth organisms introduced by space missions. The Mars exploration rovers have determined that standing liquid water existed on Mars for long periods of time in the past, and the Mars global surveyor mission and Mars Odyssey continue to uncover evidence about past water, ice, and the dynamic nature of the planet. Recently, the National Research Council (NRC) issued a report making recommendations to NASA concerning measures required to prevent future missions from contaminating Mars and to allow continued astrobiological exploration of the planet. Interim requirements recommended by the NRC include surface-sterilization of all spacecraft landing on Mars until "special" regions on Mars can be objectively differentiated from "non-special" regions, and a continuing evaluation of Martian environments, microbial survival, and spacecraft contamination. This paper discusses the report, its application to future NASA missions and potentially by other space agencies, and the actions required to protect Mars from Earth microbes and to support the continuing exploration of Mars