is a minimal biological interest, but which may be of intrinsic interest for the study of chemical evolution and for which documentation is required to ensure that planetary protection goals are being met. Categories III and IV apply to targets with significant biological interest, or with a potential to be contaminated. Category III applies to missions intended to make direct contact with these targets. Category IV applies to missions intended to make direct contact.

Category V applies to all missions that make contact with another solar system body and then return to Earth and is given in addition to the category assigned for the outbound phase. Category V missions can be designated either as "unrestricted Earth return," in which case they would warrant no further planetary protection requirements, or as "restricted Earth return," which might involve requirements for extensive constraints on the mission to guarantee the safety of Earth's biosphere.

NASA's program in planetary protection is represented on the international stage largely through the mediation of the International Council of Scientific Unions' Committee on Space Research (COSPAR), a nongovernmental organization that consults with the United Nations on planetary protection issues, particularly with respect