TABLE D.1 Categories and Associated Restrictions That Apply to Solar System Exploration Missions


Category I

Category II

Category III

Category IV

Category V

Type of mission

Any but Earth return

Any but Earth return

No direct contact (flyby, orbiters)

Direct contact (landers, probes)

Earth return

Target planet

Sun, Mercury, Pluto

Any except Mars, Sun, Mercury, Pluto



To be determined

Degree of concern


Documentation only

Passive bioload control

Active bioload control (more stringent for life detection mission)


Restricted Earth return:

–No impact on Earth or the Moon

–Sterilization of returned hardware

–Containment of any sample

Representative range of procedures


Documentation only

Documentation (more involved than category II)

Detailed documentation (substantially more involved than category III)


–Per category of target planet/outbound mission


Restricted Earth return:

–All category IV

–Continual monitoring of project activities

–Preproject advanced studies/research

–Possible sample containment






Unrestricted Earth return: None


SOURCE: As presented in DeVincenzi et al. (1996), with minor modifications in wording as embodied in NASA document NPG 8020.12.

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.

Cospar Policy

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

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