This document communicates NASA’s strategy and progress to learn about the Red Planet, to inform us more about our Earth’s past and future, and may help answer whether life exists beyond our home planet. Together with NASA’s partners in academia and commercial enterprises, NASA’s vision is to pioneer Mars and answer some of humanity’s fundamental questions: • Was Mars home to microbial life? Is it today? • Could it be a safe home for humans one day? • What can it teach us about life elsewhere in the cosmos or how life began on Earth? • What can it teach us about Earth’s past, present, and future?

Recent spacecraft and robotic probes to Mars have yielded data that are changing our understanding significantly about the possibility of existing or past life on that planet. Coupled with advances in biology and life-detection techniques, these developments place increasing importance on the need to protect Mars from contamination by Earth-borne organisms. To help with this effort, NASA requested that the NRC examine existing planetary protection measures for Mars and recommend changes and further research to improve such measures. This report discusses policies, requirements, and techniques to protect Mars from organisms originating on Earth that could interfere with scientific investigations. It provides recommendations on cleanliness and biological burden levels of Mars-bound spacecraft, methods to reach those levels, and research to reduce uncertainties in preventing forward contamination of Mars.

This study, commissioned by the National Aeronautics and Space Administration (NASA), examines the role of robotic exploration missions in assessing the risks to the first human missions to Mars. Only those hazards arising from exposure to environmental, chemical, and biological agents on the planet are assessed. To ensure that it was including all previously identified hazards in its study, the Committee on Precursor Measurements Necessary to Support Human Operations on the Surface of Mars referred to the most recent report from NASA's Mars Exploration Program/ Payload Analysis Group (MEPAG) (Greeley, 2001). The committee concluded that the requirements identified in the present NRC report are indeed the only ones essential for NASA to pursue in order to mitigate potential hazards to the first human missions to Mars.

Personnel representing several NASA field centers have formulated a "Reference Mission" addressing human exploration of Mars. Summarizes their work and describes a plan for the first human missions to Mars, using approaches that are technically feasible, have reasonable risks, and have relatively low costs. The architecture for the Mars Reference Mission builds on previous work of the Synthesis Group (1991) and Zubrin's (1991) concepts for the use of propellants derived from the Martian Atmosphere. In defining the Reference Mission, choices have been made. The rationale for each choice is documented; however, unanticipated technology advances or political decisions might change the choices in the future.

During 1988, the National Research Council's Space Science Board reorganized itself to more effectively address NASA's advisory needs. The Board's scope was broadened: it was renamed the Space Studies Board and, among other new initiatives, the Committee on Human Exploration was created. The new committee was intended to focus on the scientific aspects of human exploration programs, rather than engineering issues. Their research led to three reports: Scientific Prerequisites for the Human Exploration of Space published in 1993, Scientific Opportunities in the Human Exploration of Space published in 1994, and Science Management in the Human Exploration of Space published in 1997. These three reports are collected and reprinted in this volume in their entirety as originally published.