TABLE 1.1 COSPAR Planetary Protection Categories

  Category I Category II Category III Category IV
Type of mission Any but Earth return Any but Earth return No direct contact (flyby, some orbitersa) Direct contact (lander, probe, some orbitersa)
Target bodyb Not of direct interest for understanding of chemical evolution or the origin of life;
Group 1
Of significant interest relative to chemical evolution and the origin of life, but where there is only a remotec chance of contamination;
Group 2
Of interest relative to chemical evolution and the origin of life, but where there is a significantd chance of contamination;
Group 3
Of interest relative to chemical evolution and the origin of life, but where there is a significantd chance of contamination;
Group 4
Degree of concern None Record of planned impact probability and contamination control measures Limit on impact probability; passive bioburden control Limit on non-nominal impact probability; active bioburden control
Planetary protection policy requirements None Documentation: planetary protection plan, pre-launch report, post-launch report, post-encounter report, end-of-mission report Documentation: Category II plus: contamination control, organics inventory (as necessary) Documentation: Category III plus: probability of contamination analysis plan, microbial reduction plan, microbial assay plan, organics inventory
Implementing procedures such as: trajectory biasing, cleanroom, bioburden reduction (as necessary) Implementing procedures such as: partial sterilization of contacting hardware (as necessary), bioshield, monitoring of bioburden via bioassay

NOTE: Category V missions—all Earth-return—have not been included because they are not relevant to this study.

a The lifetime of a Mars orbiter must be such that it remains in orbit for a period in excess of 20 years or 50 years from launch with a probability of impact of 0.01 or 0.05, respectively.

bTarget body (Icy bodies mentioned in this report are in boldface):

Group 1: Flyby, Orbiter, Lander: Undifferentiated, metamorphosed asteroids; Io; others to be determined.

Group 2: Flyby, Orbiter, Lander: Venus; Moon (with organic inventory); Comets; carbonaceous chondrite asteroids; Jupiter; Saturn; Uranus; Neptune; Ganymede*; Callisto; Titan*; Triton*; Pluto/Charon*; Ceres; Large Kuiper belt objects (more than half the size of Pluto)*; other Kuiper belt objects; others to be determined.

Group 3: Flyby, Orbiters: Mars; Europa; Enceladus; others TBD.

Group 4: Lander Missions: Mars; Europa; Enceladus; others TBD.

*The mission-specific assignment of these bodies to Category II must be supported by an analysis of the “remote” potential for contamination of the liquid-water environments that may exist beneath their surfaces (a probability of introducing a single viable terrestrial organism of < 1 × 10–4), addressing both the existence of such environments and the prospects of accessing them. The probability target of 10–4 was originally proposed on the basis of historical precedents in the 2000 NRC report Preventing the Forward Contamination of Europa. NASA’s formal planetary protection policy has adopted this value as defined in NASA Procedural Requirements (NPR) document 8020.12C. COSPAR has discussed 10–4 as the acceptable risk for contamination and formally adopted this value in March 2011 for missions to icy bodies in the outer solar system

c In COSPAR usage, the term “remote” specifically implies the absence of environments where terrestrial organisms could survive and replicate, or that there is a very low likelihood of transfer to environments where terrestrial organisms could survive and replicate.

d In COSPAR usage, the term “significant” specifically implies the presence of environments where terrestrial organisms could survive and replicate, and some likelihood of transfer to those places by a plausible mechanism.



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