International Agreement on Planetary Protection
The problems of spreading Earth-origin biological materials to other planets and space in general, was recognized early in the space exploration programs of most countries, around the world.  In 1967 the UN Treaty on Outer Space included a paragraph which dealt with the subject.

Article IX of the United Nations Outer Space Treaty of 1967:

 “...parties to the Treaty shall pursue studies of outer space including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter and, where necessary, shall adopt appropriate measures for this purpose...”

For more details go to UN Treaty on Outer Space

In the USA, NASA developed its own planetary protection policy, and this is a model which should be followed by anyone exploring space.   It is simple, straightforward and summed up in two short statements.

The Planetary Protection Policy of NASA

Preserve planetary conditions for future biological and organic constituent exploration

• To protect Earth and its biosphere from potential extraterrestrial sources of contamination

More information on NASA Policy can be found at Astrobiology.

From these two statements NASA has developed a series of documents which sets out the ground rules and specifies what needs to be done to fulfill the policy.

NASA Planetary Protection Documents

NPD 8020.7 establishes NASA policy for planetary protection, which includes protection of planetary bodies for future exploration and of Earth from extraterrestrial sources of contamination.

NPG 8020.12 is issued to delineate a uniform set of planetary protection requirements for all NASA robotic extraterrestrial missions.  Implementation of these requirements will ensure that biological safeguards are being followed in NASA's space programs.

NPG 5340.1 provides the basic procedures for performing microbial assays for assessing contamination levels of spacecraft.

In order to carry out the policy, responsibility for its implementation must be set.


The Associate Administrator for Space Science is responsible for overall administration of NASA planetary protection policy.  The policy will be implemented by:

  • Maintaining the required activities in support of policy at NASA Headquarters
  • Assuring that the research and technology activities required to implement policy are conducted
  • Monitoring space flight missions as necessary to meet requirements for certification
In addition individual responsibility will be placed on individual Program Directors, who have to:
  • Meet requirements of planetary protection policy
  • Provide conduct of reviews, inspections and evaluations

It is also necessary to appoint a Planetary Protection Officer to whom authority is delegated:

Delegation of Planetary Protection Authority (NPD 8020.7E)

Management of NASA’s Planetary Protection policy is delegated to the Planetary Protection Officer for:

  • Prescribing standards, procedures, and guidelines applicable to all NASA organizations, programs, and activities.
  • Certifying to the Associate Administrator for Space Science and to the Administrator prior to launch, and in the case of returning spacecraft, prior to the return phase of the mission, prior to Earth entry, and again prior to release of returned materials, that:
    • All measures have been taken to meet NASA policy objectives
    • The recommendations of the regulatory agencies with respect to planetary protection have been considered and their statutory requirements have been fulfilled
    • International obligations have been met and international implications have been considered
  • Conducting reviews, inspections, and evaluations of plans, facilities, equipment, personnel, procedures, and practices.
  • Taking actions as necessary to achieve conformance with applicable NASA policies,  procedures, and guidelines.

Certain constraints may have to be placed on a mission if it is thought that any form of contamination may result.

Planetary Protection Mission Constraints

Depend on the nature of the mission and on the target planet

Depend on current knowledge, based on internal and external recommendations, "but most notably from the Space Studies Board of the National Academy of Sciences”

 Specific measures include:

  • Reduction of spacecraft biological contamination
  • Constraints on spacecraft operating procedures
  • Spacecraft organic inventory and restrictions
  • Restrictions on the handling of returned samples
  • Documentation of spacecraft trajectories and spacecraft material archiving
Planetary Protection Mission Categories (NPG 8020.12B)

Not of direct interest for understanding the process   of chemical evolution.  No protection of such planets is warranted (no requirements) Any
Of significant interest relative to the process of  chemical evolution, but only a remote chance that contamination by spacecraft could jeopardize
future exploration.
Of significant interest relative to the process of  chemical evolution and/or the origin of life or for which scientific opinion provides a significant
chance of contamination which could jeopardize a future biological experiment.
Flyby, Orbiter

Lander, Probe



Any Solar System Body Earth-Return

International collaboration that everyone is following the same policy and adopting the same standards in the exploration of outer space is vital.   There would be little point in NASA following these policies if other countries and commercial users of space do not adhere to the same rules.  Agreement is being sought through The Committee on Space Research (COSPAR).

 Committee on Space Research

  • COSPAR established by the International Council of Scientific Unions, is the interdisciplinary scientific organization concerned with international progress in space exploration.
  • COSPAR maintains a Planetary Protection Policy approved by the Council and archived with the Secretariat in Paris.
  • COSPAR’s policy development and promulgation capabilities need to be clarified and intensified to meet the requirements of currently planned international solar system exploration missions.

COSPAR Planetary Protection Activities

COSPAR has formed a Planetary Protection Panel to:

  • Develop, maintain, and promulgate planetary protection knowledge, policy, and plans to prevent the harmful effects of such contamination.
  • Through symposia, workshops, and topical meetings at COSPAR Assemblies to provide an international forum for exchange of information in this area.
  • Inform the international community, e.g., the Committee on the Peaceful Uses of Outer Space (COPUOS) of the United Nations, as well as various other bilateral and multilateral organizations, of COSPAR decisions in this area.

The details of how the policies might be carried out is important and the Space Studies Board (SSB), a branch of National Research Council (NRC), has produced a series of recommendations for specific missions.

 Recent Mars Planetary Protection Studies by the Space Studies Board

The following two studies laid the ground rules:

1992  Biological Contamination of Mars: Issues and Recommendations, which reported advice to NASA on measures to protect Mars from contamination by Earth organisms, as well as overall policy guidance.

1997  Mars Sample Return: Issues and Recommendations, which reported advice to NASA on Mars sample return missions.

 SSB Recommendations for Mars Sample Return

  • Samples returned from Mars should be contained and treated as though potentially hazardous until proven otherwise.
  • If sample containment cannot be verified en route to Earth, the sample and spacecraft should either be sterilized in space or not returned to Earth.
  • Integrity of sample containment should be maintained through reentry and transfer to a receiving facility
  •  Controlled distribution of unsterilized materials should only occur if analyses determine the sample not to contain a biological hazard.
  •  Planetary protection measures adopted for the first sample return should not be relaxed for subsequent missions without thorough scientific review and concurrence by an appropriate independent body.
  • Avoiding contamination of returned samples with organisms or organic material of terrestrial origin:  “It will be important to stringently avoid the possibility that terrestrial organisms, their remains, or organic matter in general could inadvertently be incorporated into sample material returned from Mars.  Contamination with terrestrial material would compromise the integrity of the sample by adding confusing background to potential discoveries related to extinct or extant life on Mars….  Because the detection of life or evidence of pre biotic chemistry is a key objective of Mars exploration, considerable effort to avoid such contamination is justified.”
  • In-flight sterilization.
Sample handling and preservation

Two issues were considered important:

  • Ensuring sample containment
  • Avoiding return of uncontained martian material

Planetary Protection Requirements for Sample Return (1)

Sterilization of outbound spacecraft (Category IV-B)

  • Concern is that terrestrial contamination of the returned sample may precipitate “false positive” in the search for evidence of extraterrestrial life, or in the hazard determination protocol.
  • Departures from sterilization requirement must be justified by thorough modeling and/or experimentation.

Clean/sterilize spacecraft surfaces that will come into contact with sample, and keep them clean

  • Prevention of recontamination/cross-contamination is the hard part.
  • If contamination cannot be avoided, it needs to be extensively characterized.
  • An inability to unequivocally identify a viable entity in the sample as Earth-life may mean that an unsterilized sample can never be released from containment.

Planetary Protection Requirements for Sample Return (2)

Sealed Extraterrestrial sample container

  • Prevent accidental release into Earth’s environment (the technical challenge may be to confirm that the sample is sealed).
Design multiple means for sealing the container (multiple layers)
  • Provide for fail-safe maintenance of seal in various Earth-landing modes.
  • Provide for initial verification that design performed sealing action, and verify only anomalous indications and non-nominal situations.
  • If verification of seal and completion of nominal operations cannot be demonstrated, then Earth return must be abandoned.

Planetary Protection Requirements for Sample Return (3)

  •  Break the chain of contact with the planetary body:
    • Preclude any “hitchhiker” entities traveling with the returned vehicle (and not contained within the sealed sample container).
  • Design for Mars isolation in sample canister loading, launch, and transfer operations:
    • Avoid recontamination during sample-transfer operations subsequent to Mars Return Vehicle launch.
    • Provide additional containment of sample canister within Earth Return Vehicle.

Planetary Protection Requirements for Sample Return (4)

Quarantine and testing

  • Contain unsterilized samples until required “biohazard” testing is completed.
  • Conduct initial characterization of returned samples and allocate portion for biohazard determination.
  • Allocate sterilized samples for special testing prior to distribution of unsterilized sample portion (may be necessary for completion of biohazard testing, as well).
  • Avoid Earth contamination of the sample throughout sample receiving, initial characterization, biohazard testing, and subsequent curation and distribution.

 Current Mars Planetary Protection Study by the Space Studies Board

  • Certification and Curation of Martian Samples.
  • Committee on Planetary and Lunar Exploration.
Requirements for a quarantine and biosafety certification facility for extraterrestrial samples, with the central question:
  • What are the criteria that must be satisfied before samples can be released from the quarantine facility?
Closely related issues include:
  • What are the optimal techniques for isolating and handling planetary materials, determining their content of biota (if any), and carrying out basic geochemical characterization studies in the certification facility?
  • How much capability for scientific analysis beyond that required for biosafety certification should be incorporated into the facility, and what principles should govern the utilization of this scientific capability?
  • To what extent can valuable lessons be learned from the Apollo quarantine experience?

In addition to Mars, a mission to the Jupiter moon, Europa, is planned and attention is now being paid as to its protection from contamination.

NRC Study: Preventing the Forward Contamination of Europa

The NRC Space Studies Board task group is evaluating the planetary protection requirements and methods used to prevent forward contamination of Europa in future orbiter and lander missions and will recommend any necessary changes. Specifically, they will:

  • assess the levels of cleanliness and sterilization required to prevent forward contamination of Europa given Europa's unique environment and our current understanding of terrestrial microorganisms;
  • review methods used to achieve the appropriate level of cleanliness and sterilization of spacecraft and recommend alternatives in light of recent advances in science and technology; and,
  • identify scientific investigations that should be accomplished to reduce the uncertainty in the above assessment.

 Europa Orbiter Science Objectives

Group 1 Objectives:

  • Determine the presence or absence of a subsurface ocean;
  • Characterize the three-dimensional distribution of any subsurface liquid water and its overlying ice layers; and,
  • Understand the formation of surface features, including sites of recent or current activity, and identify candidate landing sites for future lander missions.

Group 2 Objectives:

  • Characterize the surface composition, especially compounds of interest to pre biotic chemistry;
  • Map the distribution of important constituents on the surface; and
  • Characterize the radiation environment in order to reduce the uncertainty for future missions, especially landers.

  Recommendations: NRC Report on Small Body Sample-Return

All samples returned from planetary satellites and small solar system bodies that must be contained should be treated as potentially hazardous until proven otherwise.

No sample containment and handling is warranted beyond what is needed for scientific purposes for:

  • Moon, Io, new comets, Interstellar Dust Particles (IDP)* with a High Degree of Confidence
  • Phobos, Deimos, Callisto, C-type asteroids, undifferentiated metamorphosed asteroids, differentiated asteroids, all other comets, IDP’s* with a Lesser Degree of Confidence
  • Strict containment and handling are warranted for:
  • Europa, Ganymede, P-type asteroids, D-type asteroids, IDP’s*
  • Sample return provisions for contained samples are the same as for Mars
  *Depending on parent body and time of exposure to space environment

 Planetary protection measures adopted for the first sample return should not be relaxed for subsequent missions without thorough scientific review and concurrence by an appropriate independent body.  For samples returned from bodies where a Lesser Degree of Confidence is indicated for containment and handling, a conservative, case-by-case approach should be used to assess the containment and handling requirements

NASA should consult with or establish an advisory committee with expertise in the planetary and biological sciences relevant to such an assessment

NASA should consult with or establish an advisory committee of experts from the scientific community when developing protocols and methods to examine returned samples for indicators of past or present extraterrestrial life forms

Our thanks go to Dr John Rummel,  NASA's Planetary Protection Officer, for the content of this page.


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