Protecting solar system bodies from contamination by Earth life has been an active research topic since the start of the space race. The prospect of finding and possibly contaminating extraterrestrial life has caused the Committee on Space Research (COSPAR) to set technical standards for planetary protection; planetary protection is essential to preserve humanity’s ability to study other worlds in their natural states, to avoid contamination that would obscure the ability to find life elsewhere, and to ensure that Earth’s biosphere is protected from alien life. Until recently, these utilitarian considerations have been sufficient in addressing all ethical concerns while exploring outer space. However, the prospect of terraforming Mars has sparked a debate over the ethical implications of destroying possible alien organisms. This paper provides a historical background regarding the ethical considerations in human space exploration and argues that the utilitarian considerations provided by the NASA Office of Planetary Protection are sufficient for answering ethical questions regarding planetary protection within the solar system.
Just ten years after Sputnik 1 became the first satellite to orbit earth, representatives from the United States, United Kingdom, and Soviet Union met to formally ratify guidelines on the usage of outer space. The resulting document, the Outer Space Treaty of 1967, outlines the basic legal framework of international space law. The primary purpose of the treaty was to bar states from placing nuclear weapons in outer space and forbid governments from claiming a celestial source as their own. However, this treaty has other important implications. In ratifying this treaty, the world powers agreed that all celestial resources are the common heritage of mankind and that all exploration of celestial bodies “be conducted so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial material” . As summarized by Crawford, the treaty states that spacefaring nations must avoid biological contamination of other planetary systems and protect the Earth from potential harm caused by materials returned from space .
This prevention of biological cross-contamination is called planetary protection. Planetary protection is a critical part of planning all extraterrestrial missions. Rules and technical standards for planetary protection are prepared by an international group known as the Committee on Space Research (COSPAR). These regulations are adhered to by nearly all spacefaring nations. In the United States, the NASA Office of Planetary Protection researches planetary protection and ensures that all NASA missions adhere to all related COSPAR standards. The NASA Office of Planetary Protection argues that planetary protection is 1) essential to preserve mankind’s ability to study other worlds in their natural states, 2) necessary to avoid contamination that would obscure mankind’s ability to find life elsewhere, and 3) necessary to ensure the Earth’s biosphere is protected from alien life .
These three arguments are a summary of the main considerations given by scientists and ethicists in preventing biological cross-contamination. These considerations, which have largely not changed since the Outer Space Treaty of 1967, have been sufficient in answering all ethical questions regarding biological space exploration up to present day. However, they neglect other ethical considerations that will be important as more complex life is found outside of planet earth.
This paper provides a historical background of planetary protection, analyzes utilitarian arguments for planetary protection, introduces rights-based arguments, and argues that the utilitarian considerations provided by the NASA Office of Planetary Protection are sufficient in answering all ethical questions for planetary protection inside the solar system.
The slow development of planetary protection ethics reflects the slow development of its need. When the Apollo 11 crew and their hail of moon rocks returned to earth, they were immediately isolated in a Mobile Quarantine Facility onboard the aircraft carrier that picked them up. Scientists were unsure what kind of life – if any – thrived on the moon and what effects it would have on terrestrial life. Upon returning to the United States, the astronauts were held in quarantine for another two weeks while undergoing extensive medical evaluation. Ultimately, years of testing found no indication of life on the moon rocks, and the astronauts contracted no diseases from lunar material. Thus, quarantining moon explorers is no longer standard procedure .
The next major step in understanding planetary protection came from the Viking mission in the mid-1970s. To prevent forward contamination of Earth life with Mars, the two Viking landers were extensively sterilized. The level of sterilization the Viking landers endured was unprecedented and has become the gold standard of planetary protection. Each lander was enclosed in a pressurized shield and then sterilized at 232 °F for 40 hours to destroy all terrestrial biological material on the spacecraft. This protection was purely utilitarian: sterilizing the craft prevented the Viking biological experiments from detecting stow-away Earth life. Ultimately, the Viking landers found no sign of life, and all Mars lander missions adhere to Viking-level sterilization.
Since the Viking missions, little has changed regarding the exploration of extraterrestrial biological material. Consequently, little has changed in the ethical debate surrounding planetary protection. The reason for avoiding back contamination is clear—mankind wants to protect terrestrial life from potentially harmful alien life. But do we have an ethical obligation to protect alien life from potentially harmful terrestrial life? Until recently, this question had no practical application and was largely unaddressed. But the new prospect of terraforming Mars has given rise to the discussion that alien life may have rights, too.
Before discussing rights-based ethical considerations in dealing with extraterrestrial life, a brief overview of the utilitarian arguments for planetary protection will be made. In conducting biological experiments on celestial bodies, it makes sense to prevent the inadvertent introduction of terrestrial life. Rogue terrestrial life can return false positives on biological experiments or, if the terrestrial organisms can survive, change the chemical composition of their new ecosystem. As noted by Williamson , the space environment is much more fragile than the Earth environment. And unlike Earth ecosystems, space ecosystems most likely would not be able to regenerate after catastrophic damage from terrestrial life. For the same reason, space missions that come into contact with multiple bodies may need to be sterilized between missions to prevent one celestial body’s biological material from contaminating another celestial body later in the mission.
Before 1990, the above utilitarian arguments were the only ethical considerations seriously discussed in the scientific community. But in the early 1990s, terraforming – altering another planet’s ecosystem to support human life – became a feasible option for Mars. This spurred ethical debates regarding the rights of extraterrestrial organisms. Two major positions arose: a biocentric position, which argues that if indigenous alien life is found on a celestial body, all Earth life should be removed and mankind has an ethical responsibility to aid the spread of alien life, and an anthropocentric position, which argues that humanity has a moral obligation to make other worlds suitable for Earth life
Biocentrists active in the planetary protection debate can be divided into two groups, which will, for the purpose of this paper, be called strong biocentrists and ecocentrists. Strong biocentrists, such as Richard Sylvan, are a very small minority. They argue that all life has a right to evolve in its home biosphere at its own pace, free of any outside interference. This position claims that objects such as rocks and all microbial earth life have rights. Understandably, this position is held by only a few ethicists
Ecocentrists, most notably Christopher McKay, argue that just as individual terrestrial microbes have no rights, individual Martian microbes have no rights. However, the entire biosphere has a right to expand and should not be subject to negative interference by terrestrial life. Furthermore, McKay argues that humans have an ethical obligation to alter the Martian environment to enhance the expansion of alien life within its biosphere. Expanding this life not only supports the right of the biosphere to expand but also allows humans to enjoy the scientific and aesthetic benefits of a biologically richer solar system .
Anthropocentrists believe that humanity has a moral obligation to make other worlds suitable for Earth life as a continuation of the natural process of life transforming its surroundings to suit its needs. They also point out that humanity has a right to proliferation and so must terraform other worlds to prevent its extinction. By its very nature, terraforming alters the existing ecosystem, therefore humanity has a right to alter the existing ecosystem.
Furthermore, anthropocentrist Robert Zubrin argues that if alien life is biologically related to Earth life through a common origin, competition between alien and Earth life is not fundamentally different from that of competing microbes on Earth. Even if alien microbes have rights, humans should not take their rights into consideration because humans do not take terrestrial rights into consideration. Humans may even have an ethical responsibility to the rest of Earth’s biosphere to expand to other worlds. Humans are the unique means through which Earth life can spread beyond Earth. As Zubrin says, “Countless beings have lived and died to transform the Earth into a place that could create and allow human existence. Now it’s our turn to do our part” .
The above rights-based arguments are crude and neglect many important considerations. Ecocentrists are correct in ascribing individual alien microbes the same rights as terrestrial microbes but contradict themselves by ascribing microbial ecosystem rights important enough to be compared to the rights of sentient humans. Furthermore, ethicists disagree on whether groups or organisms can even be ascribed rights, so arguments based on assigning an entire ecosystem rights cannot be used as a main argument for or against planetary protection.
The anthropocentrist argument does not necessarily contradict itself, but assigning humans an ethical responsibility to proliferate across the rest of the Earth’s biosphere as debt for its existence is far-fetched. If humanity has this responsibility, the utility of space exploration causing the proliferation of Earth life pales in comparison to the utility of improving the Earth environment. Furthermore, humanity is in no immediate danger of extinction, so it makes no sense to use proliferation as an argument for neglecting alien life.
In short, rights-based arguments for planetary protection are negligible compared to utilitarian considerations. The utilitarian considerations summarized by the NASA Office of Planetary Protection far outweigh any of the present rights-based arguments. Planetary protection has immediate and practical benefits, whereas rights-based arguments seem to apply only to sentient organisms. The likelihood of sentient organisms existing on another celestial body within the solar system is so small that no ethical framework needs to be developed for planetary protection from other sentient beings.
By John Rising
 Anonymous. “NASA Office of Planetary Protection.” National Aeronautics and Space Administration. [Online], (2013 Spring), Available at HTTP: http://planetaryprotection.nasa.gov/
 R. Crawford. “Microbial Diversity and Its Relationship to Planetary Protection,” Applied and Environmental Microbiology, vol. 71, no. 8, 2004.
 D.P. Glavin, J.P. Dworkin, M. Lupisella, G. Kminek, and J.D. Rummel. “Biological contamination studies of lunar landing sites: implications for future planetary protection and life detection on the Moon and Mars,” International Journal of Astrobiology.
 M. Williamson, “Space ethics and protection of the space environment,” Space Policy, no. 19, 2003.
 C. McKay and R. Zubrin, “Do Indigenous Martian Bacteria have Precedence over Human Exploration?” On to Mars: Colonizing a New World, New York: Apogee Books Space Series, 2002.
 R. Zubrin, The Case for Mars: The Plan to Settle the Red Planet and Why We Must, 1st ed. New York: Simon & Schuster, 1996.