Planetary Protection

Planetary Protection is the practice of protecting solar system bodies from contamination by Earth life and protecting Earth from possible life forms that may be returned from other solar system bodies. NASA’s Office of Planetary Protection promotes the responsible exploration of the solar system by implementing and developing efforts that protect the science, explored environments and Earth. 

NASA's Planetary Protection policies and requirements ensure safe and verifiable scientific exploration for extraterrestrial life. The main objectives are to

  • Carefully control forward contamination of other worlds by terrestrial organisms and organic materials carried by spacecraft in order to guarantee the integrity of the search and study of extraterrestrial life, if it exists.
  • Rigorously preclude backward contamination of Earth by extraterrestrial life or bioactive molecules in returned samples from habitable worlds in order to prevent potentially harmful consequences for humans and the Earth’s biosphere.

To accomplish these goals, the Office of Planetary Protection assists in the construction of sterile (or low biological burden) spacecraft, the development of flight plans that protect planetary bodies of interest, the development of plans to protect the Earth from returned extraterrestrial samples, and the formulation and application of space policy as it applies to Planetary Protection.

Planetary Protection works in conjunction with solar system mission planners in order to ensure compliance with NASA policy and international agreements. Ultimately, the objective of Planetary Protection is to support the scientific study of chemical evolution and the origins of life in the solar system.

Additional information regarding Planetary Protection can be found on the Committee on Space Research website

Planetary Protection History

  • NASA to Discuss Planetary Protection Review’s Findings and Recommendations

    NASA recently announced a media teleconference that will take place at 3:30 p.m. Eastern, Friday, Oct. 18, to discuss recommendations presented by the Planetary Protection Independent Review Board, established in June 2019 by Thomas Zurbuchen, associate administrator for the agency’s Science Mission Directorate. 

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  • Planetary Protection Welcomes New Deputy Officer

    The Office of Safety and Mission Assurance recently named Elaine Seasly as the deputy Planetary Protection Officer. In this role, she will be supporting the Office of Planetary Protection in its efforts to promote the responsible exploration of the solar system by implementing and developing efforts that protect the science, explored environments and Earth.

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  • Learn More: Planetary Protection Policies and Practices Course

    NASA’s Planetary Protection program offers the course “Planetary Protection: Policies and Practices” one to two times a year, with the next offering being Oct. 30-Nov.1, 2018 at Kennedy Space Center. This course, which has been active for more than 15 years, covers what the requirements are for Planetary Protection for robotic missions, how to meet those requirements and lessons learned from past missions.

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Lisa Pratt 

Lisa Pratt

Planetary Protection Officer

Learn more about Planetary Protection Officer Lisa Pratt.

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Points of Contact

For details on contacting a Planetary Protection Point of Contact (PoC), click below.

Find Your PoC

Upcoming Events

43rd COSPAR Scientific Assembly
August 15, 2020 - August 22, 2020

The Committee on Space Research (COSPAR) is holding "43rd COSPAR Scientific Assembly," Aug. 15-22, 2020, at the International Convention Centre in Sydney, Australia. The deadline for early-bird registration is May 16, 2020. Visit for more details.


Instructor-Led Courses

Planetary Protection: Policies and Practices

This course covers what the requirements are for Planetary Protection for robotic missions, how to meet those requirements and lessons learned from past missions.

Course Details

Policy and Guidance


Policy Title Buttons Buttons

Handbook for the Microbial Examination of Space Hardware

NASA-HDBK-6022 Details See NASA-HDBK-6022
NPD 8020.7 Biological Contamination Control for Outbound and Inbound Planetary Spacecraft NPD 8020.7 Details See NPD 8020.7
NPR 8020.12 Planetary Protection Provisions for Robotic Extraterrestrial Missions NPR 8020.12 Details See NPR 8020.12

International Policy

Planetary Protection is an agreed international practice that is defined by the United Nations; promulgated by the Committee on Space Research; and practiced by space-faring agencies such as NASA, the European Space Agency, Japanese Aerospace Exploration Agency, and others.


Planetary Protection requirements are specific to the type of mission and explored planetary bodies. Accordingly, NASA assigns each mission a Planetary Protection Category based on the type of planned encounter (e.g., flyby, orbiter or lander) and the type of planetary bodies that are encountered and explored during the mission (e.g., planet, moon, comet or asteroid). In general, the Planetary Protection Categories (Categories I-V) are organized to reflect the degree a target (or encountered) planetary body may provide clues regarding life or prebiotic chemical evolution and can be further refined through planetary target and type of mission. When exploring a target body that may provide clues to the process of chemical evolution and/or the origin of life, spacecraft will have a higher level of cleanliness, with the mission providing detailed operating procedures. When exploring a target body that potentially supports Earth life, spacecraft will undergo stringent cleaning and sterilization processes and may be subject to certain operating restrictions. Planetary Protection requirements and mission categories are based on the scientific advice of the Space Studies Board and on NASA or international policy guidelines.

Category Planetary Body Mission Mission Status
Sun Ulysses  Completed
II Sun Solar Orbiter Collaboration Planning Phase
II Jupiter Galileo Completed
II Jupiter Juno Ongoing
II Jupiter/Saturn Pioneer 10 and 11 Completed
II Jupiter/Saturn/Heliosheath Voyager Ongoing
II Mercury (Venus fly-by) MESSENGER Completed
II Moon Chandrayaan-1/ISRO (M3)  Completed
II Comets Tempel 1 & Hartley 2 Deep Impact/EPOXI Ongoing
II Moon Clementine Completed
II Moon Grail Completed
II Moon LADEE Completed
II Moon Lunar Prospector Completed
II Moon Lunar Reconnaissance Orbiter Ongoing
II Moon Ranger 1-9 Completed
II Moon Surveyor  Completed
II Pluto/Charon New Horizons Ongoing
II Saturn Cassini-Huygens Completed
II Comets Encke, Schwassmann-Wachmann-3 and d'Arrest. CONTOUR Failed
II Asteroid Eros NEAR-Shoemaker Completed
II Venus Magellan Completed
II Venus Pioneer-Venus Completed
II 1 Moon Chang'e-3/CNSA Ongoing
III Mars Mars Express/ESA (ASPERA-3) Ongoing
III Mars Viking 1-2 Orbiters Completed
III Asteroids Vesta & Ceres (Mars flyby) Dawn Ongoing
III Europa Europa Clipper Planning Phase
III Mercury, Venus, Mars Mariner Missions Completed
III Mars Mars Climate Orbiter Failed
III Mars MAVEN Ongoing
III Mars Mars Global Surveyor Completed
III Mars Mars Observer Failed
III Mars Mars Odyssey Ongoing
III Mars Mars Reconnaissance Orbiter Ongoing
III (II-comet) Comet C-G, Asteroid Lutetia Rosetta  Ongoing
III (II-comet) Comet Borrelly Deep Space 1 Completed
III (TGO), IVa (EDM) Mars ExoMars 2016/ESA: Trace Gas Orbiter (TGO) and Entry, Descent, and Landing Demonstrator Module (EDM) Ongoing
III 1 Mars Mars Orbiter Mission (Mangalyaan)/ISRO Ongoing
III 1 Mars Mars Orbiter Mission/ISRO Ongoing
IVa Mars Deep Space 2 Failed
IVa Mars Mars Pathfinder Completed
IVa Mars Mars Polar Lander Failed
IVa Mars Mars Science Laboratory Ongoing
IVa Mars MER Opportunity  Ongoing
IVa Mars MER Spirit  Completed
IVa Mars InSight Ongoing
IVb Mars ExoMars 2020/ESA Planning Phase
IVb Mars Viking 1-2 Landers Completed
IVc Mars Mars Phoenix Lander Completed
V (restricted) Moon Apollo 11, 12, 14 Completed
V (restricted) Mars Mars 2020 Planning Phase
V (unrestricted) Asteroid 25143 Itokawa Hayabusa/JAXA  Completed
V (unrestricted) Asteroid 1999 JU3 Hayabusa 2/JAXA Ongoing
V (unrestricted) Asteroid 1999 RQ36 OSIRIS-REx Ongoing
V (unrestricted) Comets Wild 2 & Tempel 1 Stardust NExT Completed
V (unrestricted) Heliosphere Genesis Completed
V (unrestricted) Moon Apollo 15-17 Completed

Mission Categories

Protecting Life on Other Bodies

Planetary Protection requirements for each mission and target body are determined based on the scientific advice of the Space Studies Board and on NASA or international policy guidelines. Each mission is categorized according to the type of encounter it will have (e.g., flyby, orbiter or lander) and the nature of its destination (e.g., a planet, moon, comet or asteroid). If the target body has the potential to provide clues about life or prebiotic chemical evolution, a spacecraft going there must meet a higher level of cleanliness and some operating restrictions will be imposed. Spacecraft going to target bodies with the potential to support Earth life must undergo stringent cleaning and sterilization processes and greater operating restrictions.

Mission Design and Planning

Compliance with Planetary Protection requirements is mandatory for NASA missions, per NPD 8020.7, Biological Contamination Control for Outbound and Inbound Planetary Spacecraft. The first and most important step in complying with NASA Planetary Protection policy is avoiding unintended encounters with solar system objects. As described in NPR 8020.12, Planetary Protection Provisions for Robotic Extraterrestrial Missions, missions must meet a certain set of forward contamination criteria including

  • Limiting the probability that a planetary body will be contaminated during the period of exploration to no more than 1×10 -3 (unless otherwise specified), where the period of exploration shall extend at least 50 years after a Category III or IV   mission arrives at its protected target (and no longer than the time point after which no organisms remain viable on the spacecraft)
  • Avoiding impact of Mars over a time period of 50 years with a probability of < 1×10 -2 for spacecraft that cross the orbit of Mars en route to other targets and < 1×10 -4 for all launch elements that leave Earth’s orbit
  • Avoiding impact of target bodies, including orbital lifetime constraints
  • Minimizing the probability of contamination using mission-dependent pre- and post-launch approaches, such as cleanroom usage, aseptic assembly of spacecraft, partial sterilization of spacecraft components and trajectory biasing.

Careful mission design and planning are essential elements when considering Planetary Protection requirements, which are both mission and target body dependent. Consultations with the Planetary Protection Officer (PPO) during mission development is critical in ensuring compliance with NASA policy. 

Mission Gallery

View the Mission Gallery for photos of NASA programs and projects that are implementing or have implemented Planetary Protection requirements. 

See Gallery 

Conference Documents

Conference/Event Date Description Agenda Report
2nd COSPAR Workshop on Refining Planetary Protection Requirements for Human Missions 5/15/18-5/16/18 Committee on Space Research (COSPAR) Workshop   See 2018 Report
Refining Planetary Protection Requirements for Human Missions 10/25/16-10/27/16 NASA workshop, cosponsored by the NASA Science Mission Directorate and Human Exploration and Operations Mission Directorate   See 2016 Report
Planetary Protection Knowledge Gaps for Human Extraterrestrial Missions 3/24/15-3/26/15 Committee on Space Research Workshop, cosponsored by the NASA Human Exploration and Operations Mission Directorate   See 2015 Report

Solar System Bodies

Solar system bodies for which NASA has considered Planetary Protection precautions include Venus; Earth; Earth’s moon; Mars; Jupiter; Europa, Ganymede, and Callisto (moons of Jupiter); Titan and Enceladus (moons of Saturn); comets, and asteroids.

Additional Information