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Planetary Protection

Catriona McDonald: Habitability in the Universe

Planetary Protection: What we still haven't learnt from the moon

In the early years of the Cold War and the Space Race, the scientific community began to raise concerns that in the rush to be the first nation to reach certain milestones, irrevocable damage could be done to the Solar System. The interdisciplinary Committee on Space Research (COSPAR) was founded in 1958 to consider the issue of planetary protection and provide international recommendations to avoid biological and organic contamination of other bodies, and of the Earth (Kminek, 2017). These recommendations were put into practice in 1967 when the United Nations established the Outer Space Treaty, which laid out the principles for international cooperation in the peaceful exploration and use of outer space (United Nations, 1967). In particular, Article IX of the treaty states that participant countries should “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”. As of March 2020, 109 countries have ratified the treaty (United Nations Office for Disarmament Affairs, 2020) and the treaty itself has changed very little since, even though the space industry has drastically evolved. COSPAR meet once every two years to review the current recommendations to avoid planetary contamination. The two types of planetary contamination are forward, where viable terrestrial organisms are transferred to another body, and back, where extraterrestrial organisms are bought back to Earth. The COSPAR recommendations organise all Solar System missions into five main categories (Kminek, 2017):

  • Category I: locations of no direct interest to chemical evolution or the origin of life. There are no protection requirements for these missions.
  • Category II: locations of specific interest for chemical evolution and the origin of life, but little chance contamination could compromise investigations. Only documentation outlining any potential impacts and an end of mission report are needed.
  • Category III: flyby and orbiter missions to locations of specific interest for chemical evolution and the origin of life and with a significant chance that contamination would compromise investigations. More involved documentation than Category II missions is required, and possibly clean room assembly to minimize terrestrial contaminants
  • Category IV: lander or probe missions to the same bodies as Category III. Requirements here are very stringent: documentation, an estimate of the bioburden and inventory of the bulk constituent organics present are just some of the imposed conditions.
  • Category V: all sample return missions to Earth. The main concern here is protecting Earth from destructive return impacts and ensuring that all samples returned are sufficiently contained and studied.

The Moon stands in a unique place in the Solar System as the only other body which humans have stood on. Under COSPAR regulations it is a Category II location, with no special protection requirements (Shahar & Greenbaum, 2020).

In some respects, the exploration of the Moon began the interest of COSPAR in planetary protection. In September 1959, the Soviet Luna 2 probe was deliberately crashed onto the surface of the Moon. The probe had not been sterilised and led to concerns that terrestrial bacteria on the spacecraft could cause irreversible changes to the lunar environment and greatly affect future scientific exploration (Glavin, et al., 2004). From then on, NASA probes were sterilised with prolonged heat exposure. However, the sterilisation process was found to be the cause of multiple craft failures. So, NASA relaxed their procedures and stopped sterilising their probes to the same levels. Was this step due to a decreased worry about contamination, or the need to dominate in the Space Race?

Concerns about contaminating the Moon had abated at the time of the Apollo missions, however, some specific concerns remained. After President Kennedy gave the challenge of landing a man on the Moon by the end of the 1960s, a committee was convened to address the issue of Lunar back contamination. When the Apollo 11 command module returned to Earth and splashed into the sea, the crew members were put in biological isolation garments, sprayed liberally with germicidal solution, and held in quarantine for 21 days (Allton, et al., 1998).

Although there were clear precautions put in place to avoid damage to Earth, the same cannot be said for the Moon. Alongside the famous US flags and golf balls hit by Alan Shephard from Apollo 14, there are large amounts of technical equipment just abandoned, as well as bags of human waste. The idea being, that in order to bring back the over 350kg of lunar samples the Apollo missions recovered, the astronauts needed to lighten the lift off weight (Heiney, 2004).

The current protection policies for the Moon are so weak because it is believed that the lunar surface is just too hostile for organisms to survive. However, it is thought that in sheltered areas, such as craters, terrestrial organisms could survive. As an example, the 1999 Lunar Prospector mission was purposefully crash landed into a crater near the lunar south pole. The lander wasn’t sterilised, and any terrestrial bacteria which survived impact could still be viable, shaded by the Sun’s intense UV radiation. Even if terrestrial organisms become inactive on the lunar surface, they could still leave biomarkers in the soil which could be identified by future investigations. Analysis of soils returned by the Apollo missions indicated that terrestrial contaminants are detectable at concentrations up to 70 parts per billion after the later missions (Glavin, et al., 2004).

The contamination of the lunar surface didn’t end with the Apollo missions. In the last two years organisms have twice been purposefully sent to the Moon. In 2018, the Chinese Chang’e 4 moon lander landed on the far side of the Moon and contained an artificial biosphere aiming to establish an ecosystem of germinating plants and insects (David, 2018). After landing, some cotton seeds were seen to be sprouting. The onset of lunar night after 9 days however, bought an end to the experiment as temperatures became too low (Jones, 2019). In February of the following year, an Israeli non-profit organisation, SpaceIL, launched a mission to the Moon known as Beresheet. Upon the craft’s final descent to the lunar surface in April 2019, it crashed (Skyldkrot, et al., 2019). Included in the payload of this mission was the Lunar Library, created by the US based Arch Mission Foundation, whose goal is to project the culmination of human knowledge into space (Arch Mission Foundation, 2019). The Lunar Library included a nanodisc with a 30 million page archive of human history, samples of human DNA and a batch of tardigrades embedded within multiple layers of metal and a specially slow cured resin (Caplin, 2019).

Tardigrades are near-microscopic extremophile animals which can survive in just about any environment. Their survival comes down to self-inducing a state of cryptobiosis, where they curl into a dehydrated ball known as a tun. If the inanimate tardigrade comes into contact with water, they can come back to life in hours (Bradford, 2017). It is possible that during the crash landing the container holding the tardigrades broke open and released them onto the surface. While tardigrades are notoriously hardy and have been shown to be able to survive in space, there has been studies that show it is unlikely that tardigrades would be able to survive on the Moon. A 2007 experiment saw a sample of tun-state tardigrades spend 12 days in low Earth orbit. It was found that tardigrades could easily survive the vacuum of space, but samples that were exposed to both vacuum and equivalent ultraviolet radiation from the Sun, survived for up to only a week after being rehydrated (Jonsson, et al., 2008). The tardigrades on the Moon would also need to encounter water to reanimate. An extremely unlikely direct collision of an icy comet could provide the necessary water, however, the tardigrades would not be able to survive the lunar radiation, let alone have any food to sustain themselves (Caplin, 2019). In any case, sending a collection of some of the toughest organisms on Earth to the Moon seems like a reckless move.

Five months after the launch of Beresheet, the Arch Mission Foundation announced that the Lunar Library contained the tardigrades and other biological material. Until that moment, not even SpaceIL were aware (Shahar & Greenbaum, 2020)This introduces the question; in the emerging world of both national and private space exploration, who is liable for protecting the Solar System? The Outer Space Treaty isn’t explicit in whether governments are required to supervise the actions of non-governmental organisations, and countries are only now beginning to look at their responsibilities in this area (Shahar & Greenbaum, 2020). The US Federal Aviation Administration investigated the Beresheet incident, as it was launched from US soil, and found that SpaceIL were not liable and the Lunar Library technically broke no laws. How is the littering of the Moon allowed to continue?

Planetary protection measures are not really there to preserve the state of the Solar System, they are there to allow human exploitation. Even the wording of the COSPAR recommendations talk about locations of specific interest to scientific advances. Why can’t the pristine Solar System be protected in the same way we have national parks on Earth? The Apollo missions may have been one giant leap for mankind that has simply 2 allowed humanity to continue polluting and exploiting the natural world.



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Caplin, N., 2019. Anything to declare?. Physics World, p. 84.

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United Nations Office for Disarmament Affairs, 2020. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies. [Online]
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United Nations, 1967. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies. s.l.:U.N. Doc. A/RES/2222/(XXI).