Solar system exploration is in an extraordinary state of expansion. Scientific capabilities to search for evidence of extant or relic life outside Earth—among the principal goals of solar system exploration—are advancing rapidly. In this time of rapid transition in exploring solar system bodies, the importance of reexamining planetary protection policies, including the need for clarity in how NASA establishes such policies, has become more urgent. Overall, this study seeks to review the current state of planetary protection policy development, assess the responsiveness of the policy development process to contemporary and anticipated needs, and recommend actions that might assure the effectiveness of NASA's future coordination and execution of planetary protection. This interim report focuses on the goals of and rationales for planetary protection policies and suggests a working definition of planetary protection consistent with those goals. It does not address future commercial planetary missions, human missions to planetary bodies, or roles and responsibilities for implementing policies, but these issues will be addressed in the final report.