Elsevier

Acta Astronautica

Volume 66, Issues 5–6, March–April 2010, Pages 792-797
Acta Astronautica

Planetary protection for human exploration of Mars

https://doi.org/10.1016/j.actaastro.2009.08.015Get rights and content

Abstract

Human astronauts have unique capabilities that could greatly facilitate scientific exploration of other planets. However, when searching for life beyond Earth, these capabilities can be utilized effectively only if the biological contamination associated with human presence is monitored and minimized. This is termed planetary protection, and is a critical element in human exploration beyond Earth. Planetary protection must be incorporated from the earliest stages of mission planning and development, to ensure proper implementation. Issues involve both “forward contamination”, the contamination of other solar system bodies by Earth microbes and organic materials, and “backward contamination”, the contamination of Earth systems, including astronauts, by biological hazards or potential alien life. Conclusions from a number of international workshops held over the last six years recognize that some degree of forward contamination associated with human astronaut explorers is inevitable. Nevertheless, when humans are exploring space the principles and policies of planetary protection, developed by COSPAR in accordance with the 1967 Outer Space Treaty, still apply. Implementation guidelines include documenting and minimizing contamination of the exploration targets, control at the most stringent levels for locations in which Earth life might grow, and protection of humans from exposure to untested planetary materials. Preventing harmful contamination of the Earth must be of the highest priority for all missions.

Introduction

When searching for life beyond Earth, the unique capabilities of human astronauts can be utilized effectively only if biological contamination associated with human presence is understood and controlled. Regulating biological contamination during planetary exploration is termed planetary protection, and will be a critical element in the human exploration of other solar system bodies. Planetary protection must be incorporated from the earliest stages of mission planning and development, to ensure proper implementation. Issues of concern to planetary protection involve both “forward contamination”, which is the contamination of other solar system bodies by Earth microbes and organic materials, and “backward contamination”, which is the contamination of Earth systems by potential alien life. Forward contamination involves contamination that might invalidate current or future scientific exploration of a particular solar system body, and that might disrupt the planetary environment or a potential endogenous (alien) ecosystem. Backward contamination involves the potential for harmful contamination of the Earth, and for human missions includes the possible immediate and long-term effects on the health of the astronaut explorers from possible biologically-active materials encountered during exploration.

A number of national and international workshops held over the last six years [1], [2], [3], [4] have generated a consensus regarding planetary protection policies and requirements for human missions to Mars, and a 2007 workshop held by NASA has considered the issues and benefits to planetary protection that might be offered by a return to the Moon [5]. Conclusions from these workshops recognize that some degree of forward contamination associated with human astronaut explorers is inevitable. Nevertheless, the principles and policies of planetary protection, developed by the Committee on Space Research (COSPAR) in accordance with the 1967 Outer Space Treaty, can and should be followed when humans are exploring space.

Implementation guidelines include documenting and minimizing contamination of the exploration targets, protection at the most stringent levels for any target locations in which Earth life might grow, protection of humans from exposure to untested planetary materials, and preventing harmful contamination of the Earth as the highest priority of all missions. These principles should be incorporated in frameworks for future international missions of human exploration. It would be a tragic medical accident were an astronaut on the way to Mars get sick of unknown causes. It would be far more tragic, and of significant concern for planetary protection, should one of several astronauts become ill on the return from Mars to Earth, without sufficient medical information to determine why.

Section snippets

International basis for planetary protection policy

Planetary protection entered into international law with Article IX of the 1967 Outer Space Treaty, which states in part that:

“…parties to the Treaty shall pursue studies of outer space including the Moon and other celestial bodies, and conduct exp loration 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…”

COSPAR policy on human missions

The introduction to the COSPAR policy on planetary protection recognizes that the primary goals of planetary protection, protecting the Earth and preventing forward and backward contamination, do not change when humans are involved. However, the essential association of humans with commensal microbes requires that certain variations will have to be developed in order to implement planetary protection on human missions. To mitigate the potential for danger to astronauts and to Earth, planetary

Implementation guidelines

In addition to general principles on human exploration, COSPAR has formulated a number of guidelines that can be used to inform the development of mission scenarios.

Guidelines for human missions to mars: In accordance with these principles, specific implementation guidelines for human missions to Mars include:

  • Human missions will carry microbial populations that will vary in both kind and quantity, and it will not be practicable to specify all aspects of an allowable microbial population or

Practical implementation

It appears premature to adopt specific requirements for human missions to Mars, but (as of July 2008) COSPAR has assembled a set of guidelines as part of, and consistent with, its consensus planetary protection policy. Locations on Mars that are consistent with current mission requirements to land on most of Mars (category IVa) are locations that likely would be allowed for human exploration, as being too cold, and too dry, for surface microbial contamination—given that EVA suits and other

Conclusions

The movement of humans off-planet is one of the hopes for sustaining our civilization and our species. Preserving that value of that movement in terms of exploration and science is an important component of human spaceflight. Planetary protection considerations are essential to protecting the Earth, and protecting the potential to perform scientific exploration of the solar system without jeopardizing investigations into the origins and evolution of life. Although humans are inevitably

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