Space missions v. environmental integrity of extra-terrestrial bodies: The conundrum of interplanetary contamination

Interplanetary contamination is the introduction of biological foreign material from one planetary body to another. Transfer of these biological materials from the Earth to any other planetary body and vice-versa can cause severe damage to its pre-existing state and can have an irreversible effect which may hamper the evolution of possible life on that body. The risks of interplanetary contamination due to the increasing number of space missions especially on Mars have been recognised by astrobiologists recently.

Article I of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space (“Outer Space Treaty” or “OST”) states that the “exploration and use of outer space….shall be carried out for the benefit and in the interest of all countries and shall be the province of all mankind.” Outer space and the celestial bodies are considered global commons for the benefit and advancement of all mankind through scientific exploration. Therefore, it becomes an ethical duty of the States to protect the outer space and the celestial bodies from contamination.

This blog delves into the concept of interplanetary contamination and highlights the existing legal framework with a special emphasis on NASA’s recent measures to protect the environment of the extra-terrestrial bodies. It further discusses some of the space missions and the risk of contamination from them.

The risk of interplanetary contamination

In the last couple of decades, it has been obvious that scientists have become obsessed with exploring extra-terrestrial bodies in search of the existence of a parallel life form. Recently, a report by the National Academies of Sciences, Engineering and Medicine observed that ‘the advent of new space activities and players in the exploration and use of space’ has increased the potential threat with regard to planetary protection. It recommends NASA to conduct research to see into the possibility of Martian exploration zone’,where the possible contamination could cause no harm to the microbial life on Mars. As per the definition of “interplanetary contamination”, it is conspicuous that the risk of interplanetary contamination exists with respect to those celestial bodies where microbial life could possibly exist. Further, interplanetary contamination is of two types: forward and back contamination.

Forward contamination

Forward Contamination is the transportation of biological material from Earth to another planetary body with space probes or human space missions. The possibility of hosting liquid water on few celestial bodies such as Mars, Enceladus and Europa suggests the possible extra-terrestrial life on these bodies and results in enabling the scientists to actively look for signs of life. In case of Mars, the exploration missions would encumber the possible life forms and further evolution of life on the Red planet. Moreover, the native life on Mars (if present) could be swamped by microbes from the Earth and these microbes may also compromise the integrity of the samples from Mars.

There are several methods that have been identified to decrease the risk of forward contamination such as sterilization of hardware items and the spacecraft; the use of material which is less affine to biological material; assessment of spacecraft contaminants; development of revised requirements for reduction of bio-burden; and improvement of bioburden reduction techniques.

Back Contamination

Back Contaminations refers to the possible introduction of foreign biological material from other planetary body to Earth. There is a lesser risk of back contamination from Mars to Earth, given the fact that there is a significant difference in the biochemistry of both the bodies. However, this fact does not turn the concept of back contamination to only a theoretical idea. Back in 1960s and 1970s during the Apollo 11 program, NASA was concerned about the potential contaminants which might travel from the Moon. Therefore, every space mission since has gone through a painstaking quarantine process of 30 days. It was found that containment is the only option as sterilisation would ruin the extra-terrestrial samples.

Planetary protection laws

Even before Sputnik, the first artificial satellite, went into space, the international community has been concerned about harming the environment of other planets as well as the risks to the Earth’s biosphere due to space explorations. Planetary protection rules, thus, entail protection of the solar system bodies from “harmful contamination”.

Committee on Space Research (COSPAR)

The International Council for Science established the Committee on Space Research (“COSPAR”) in 1958 to look into space researches undertaken worldwide. It had taken over the functions of the Committee on Extra-Terrestrial Exploration (CETEX), an ad hoc committee which had recommended establishing a code of conduct for space missions and research, keeping in mind planetary protection issues. The directions issued by COSPAR are formulated to guide the compliance with the provisions of the OST. The major problem with the COSPAR rules is that they are not legally binding which means that NASA or any other organisation is not bound to follow them. While this feature has not caused much trouble, recent reviews have raised concerns that the standards issued by COSPAR need updating to keep up with scientific progress and technological advances.

The Outer Space Treaty

The main aim with which the OST was formulated in 1967 was to ensure that the States use the outer space only for peaceful purposes. The treaty also deals with issues related to the protection of the environment of celestial bodies which can be evidenced from provisions contained under Article III and Article IV. However, the fundamental rule which is most directly applicable to planetary protection issues is Article IX (“Article”) which provides that the States shall pursue the studies and exploration of the outer space including moon and other celestial bodies in a manner that any harmful contamination in those bodies and adverse changes to the Earth’s environment are avoided. It further mentions that the States shall adopt appropriate measures for this purpose. While this has been considered as a laudable attempt to address the issue of protection of the environment of planetary bodies, the Article has been termed ambiguous. It is difficult to determine whether its focus is on the protection of the celestial bodies or the scientific interests of States. Moreover, a policy review of the treaty had concluded that the Article does not define the term “harmful contamination”, the circumstances under which “appropriate measures” need to be undertaken and which measures would be “appropriate”.

NASA’s Guidelines

NASA’s Procedural Requirement Policy categorizes missions based on the planetary protection priorities of each extra-terrestrial solar system body and the mission plan. Category I and II include those celestial bodies which are not exposed to the risk of terrestrial contamination such as the moon and asteroids. Protection of such planets is not warranted and there are no specific requirements for such missions. Category III and IV, on the other hand include those bodies which are important for the process of chemical evolution/ or origin of life and can be subject to contamination by spacecraft. A few bodies under these categories are Jupiter’s moon Europa, Saturn’s moon Enceladus and Mars. Category V involves all the “Earth-return missions”.

Due to the numerous space missions lined up, NASA established a Planetary Protection Independent Review Board (“PPIRB”) in 2019 which suggested that NASA should reconsider the categorization of missions from a planetary-protection perspective because the present system appears to be “overly broad and antiquated”. Recently, NASA issued modernized guidelines on the lines of the suggestions made by the PPIRB. However, they have not yet been formally issued by the COSPAR. Therefore, NASA issued two NASA Interim Directives (“NIDs”) to update the requirements for robotic and human missions to the Moon and Mars. The first NID reclassifies parts of the Moon and dilutes restrictions on missions landing there. Earlier, the scientists were cautious about the possibility of some form of life on the Moon and therefore, it had been categorised under Category II. However, the first directive lists some parts of the Moon under Category I missions which do not require much protection because there is no expectation of finding life. The second NID calls for updating the rules for human missions to Mars. It does not change the designation of Mars as a Category IV body since there is a high possibility of finding life there. However, it recommends the agency to conduct studies and formulate new guidelines in the light of upcoming missions to Mars.

Space missions: Past and future

As early as the Viking Project in the 1970s, which became the first US mission to land a spacecraft safely on the surface of Mars, the scientists have been cautious about interplanetary contamination. In order to sterilize the spacecraft, it was baked at high temperatures before leaving so as to kill any microbes that may attach themselves to it and contaminate the results. After successfully orbiting Saturn for almost 13 years, the Cassini spacecraft was destroyed in 2017. The death of the spacecraft was staged to ensure that Cassini never collided with one of the moons of Saturn such as Enceladus or Titan and contaminate the potentially habitable bodies.

One of the more recent missions which could pose a threat to the solar system according to experts, is the launch of Starship craft by SpaceX, a private space-faring company owned by Elon Musk. Even if rigorous planetary protection plans have been made by SpaceX, there is no mention of such a policy on their website or any public domain which implies that the company is not more focussed on the exploration than on the consequences of the same.

NASA’s Perseverance Mars rover launched on 30th July 2020, is the first interplanetary sample-return mission. While the mission is a remarkable feat for scientists, the risk of interplanetary contamination cannot be ignored. This mission followed the launch of China’s Tianewen-1 which would land on Mars’ surface, and UAE’s Al Amal (Hope), an orbital mission to study Mars’ atmosphere.


It is not only the legal duty of the States to prevent interplanetary contamination but an ethical/moral duty as well, to conserve the environment and the possible existence of life on extra-terrestrial bodies from the risk of contamination. With the increasing number of upcoming space missions, it is becoming more important to put in place effective rules in order to protect the environmental integrity of planets. The interim directives issued by the NASA are well founded as temporary relief till COSPAR considers the guidelines and decides on whether they shall be incorporated in the planetary protection guidelines of COSPAR.  Further, they seem like a step in the right direction because the aim of the directives is to achieve sustainable exploration of the Moon and the Mars while ensuring the interests of the scientific community engaged in explorations at the same time. NASA Administrator Jim Bridenstine stressed that these directives are not ‘policy’ directives but ‘interim’ directives that are “not set in stone”. Moreover, the problem that arises is that these directives issued by NASA are not applicable to other countries or the private sector. Therefore, an urgent need is felt for COSPAR to review the guidelines and incorporate them within its own guidelines at the earliest so as to make them universally applicable.

The existing framework (mainly COSPAR guidelines and the OST) governing planetary protection has worked till now because of the limited number of countries engaged in space missions. That is now changing since more countries and entities are getting involved and therefore, there is a need to relook into the existing provisions such as Article IX of the OST. The major problem that subsists is that these provisions merely apply to the state actors and not private bodies. Since there has been a tremendous increase in private companies taking up space missions, it is the need of the hour to either modify the existing framework or formulate new regulations for such bodies.

This article has been authored by Parnika Goswami and Pratyaksh Sikodia, students at National Law University, Jodhpur.

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