Irmgard Marboe (ed), Legal Aspects of Planetary Defence (Brill, 2021), 426 pages, ISBN 978-90-04-46759-0

Over a hundred million years, asteroids have impacted the Earth. These collisions have shaped our planet causing destruction and altering its surface.¹ Earth creation is pictured by numerous transformations and geological extreme events especially crashes between celestial bodies characterising the Solar System movement. Consequently, the fact that Earth is being impacted by near-Earth objects (NEOs) is inevitable. The “impactors” may refer to a harmless but potentially frequent fireball; to a largest airburst which does not cause important damage on the ground; and to a more catastrophic situation which nevertheless has little probability of occurring during the human lifetime.² NEOs refer to asteroids or comets of sizes ranging from metres to tens of kilometres that orbit the Sun and whose orbits come close to that of Earth’s.³ Around 600.000 asteroids are present in our Solar System, and more than 20.000 are NEOs. The latter could potentially hit our planet and, depending on their size, generate considerable damage. While the chance of a large object hitting Earth is very small, it would produce a great deal of destruction and for this reason, active detection and tracking efforts have to be considered. Hence, it is necessary to become aware of the current and future position of NEOs relative to our planet, to estimate the likelihood of Earth impacts, foresee their potential consequences, and develop NEO deflection methods as their impacts could lead to a cataclysm. According to the ILC Draft Articles on the ‘Protection of persons in the event of disasters’, a disaster refers to ‘a calamitous event or series of events resulting in widespread loss of life, great human suffering and distress, mass displacement, or large-scale material or environmental damage, thereby seriously disrupting the functioning of society’.⁴

In light of the definition given, NEO impact is considered a disaster leading to dramatic results on Earth from human loss of life, devastating environmental and societal effects. In this context, new technologies and systems of observation are being developed by States,⁵ agencies and private entities in order to be able to predict and cope with asteroids and comets threats. These mechanisms allow the international community to discover more and more objects that could represent an unacceptable danger and could cause dramatic and serious consequences on Earth. In that respect, NEOs’ threats and deflection missions have to be explored from legal, economic, political and societal perspectives. In particular, NEOs’ threats raise significant legal issues that need to be addressed before the international community finds unprepared against a catastrophic situation. For instance, in February 2013, an asteroid entered the atmosphere and disintegrated in the skies over Russia. The airburst overpressure wave caused widespread glass breakage, resulting in injury to approximately 1.500 people. Damages were estimated at $33 million, and the energy deployed was around 400 kilotons.⁶ More recently, in March 2022, a small object entered the Earth’s atmosphere, scooting across the sky between Greenland and Norway, a few hours after it was discovered.⁷ It is not the first time that a natural object is observed before impacting the atmosphere. NEOs’ threats and impacts are real, and their disastrous consequences should not be underestimated.

In this context, planetary defence deals with significant elements which are cross-sectoral in nature as depicted in the book, ‘Legal Aspects of Planetary Defence’. The book encompasses twenty-two chapters written by well- recognised international space law experts, with each chapter going into considerable depth on particular aspects of planetary defence. The volume, edited by Professor Irmgard Marboe and divided into two parts, achieves a comprehensive legal overview of such aspects and will be of interest and utility to those wishing to enhance their knowledge on the topic. The first part is dedicated to scientific, technical and international cooperation aspects of planetary defence. The second part furthers the variety of legal issues induced by NEOs’ threats, focusing on the obligations of States under international law and, specifically, international space law. In this way, it allows the reader to figure out first the technical and collaboration challenges before addressing the legal and policy questions.

Section one of the book entitled ‘Planetary Defence and International Cooperative Efforts’ focuses on the scientific research, and technological activities, as well as international partnerships related to NEO programmes. This first section contains eight chapters giving a comprehensive overview of the peculiarities of near-Earth object missions. NEOs have different characteristics (mass, diameters, location in the solar system), and once NEO’s trajectories have been identified there are various mitigation responses possible which depend on the nature of the object and the parameters of the potential impacts (Chapter 1, Christian Koeberl and Cordula Steinkogler). It is indeed important to identify planetary defence priorities by taking into account the classification of the NEO. Chapter 2 (Rüdiger Jehn) reflects on the numbers of NEOs in the universe and their impact frequencies. The fact is that in contrast to other natural disasters, such as earthquakes, volcanos, and hurricanes, NEOs’ impacts may be averted, in a sense that it is possible to prevent them through adequate technology. However, in reality, there is a precondition which is the “early detection” (p. 34) in order to anticipate this threat a long time in advance and to avoid any dramatic consequences. In addition, the technology used is not the “ordinary” one operated for usual disasters. As noted in Chapter 3 (Alan Harris), the method will depend on the size and density of the object, its orbit location and the time-lapse before the collision. Furthermore, as for the conduct of any space activities, international cooperation will be of utmost importance in the conduct of NEO programmes.⁸ Indeed, it would not be possible for a single State to proceed in such a mission as numerous issues will have to be considered by all actors involved (private and public), as well as by the scientific and technical communities, to prepare the components of the mission (i.e. launcher, hardware, software, and test facilities). Any attempt to deflect a hazardous asteroid would be a considerable undertaking requiring the competencies and inventiveness of many scientists, engineers, and project coordinators. In the context of an international partnership involving various stakeholders, as mentioned in Chapter 4 (Gerhard Drolshagen, Lindley N. Johnson and Romana Kofler), the United Nations Office for Outer Space Affairs (UNOOSA) and the United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS) represent the main fora for the law-making process regarding space activities, and the promotion of international cooperation in this branch. After the Third United Nations Conference on the Exploration and Peaceful Uses of Outer Space (UNISPACE III) in 1999,⁹ the international community became aware of the necessity to encourage international collaboration to improve understanding of the NEOs menace. Thus, the Scientific and Technical Subcommittee of UNCOPUOS introduced ‘Near-Earth Objects’ as a new item on its agenda and a dedicated Working Group submitted important recommendations in 2013 with the establishment of two new entities: the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG). Their objectives are to develop roadmaps, research, as well as exchange of information, legal frameworks and mitigation activities in a collaborative manner in case of deflection missions. Apart from the necessity to promote international cooperation in case of NEOs risk, there is a requirement to strengthen public awareness on this issue. Hence, as noted in Chapter 5 (Frans von der Dunk), governments, international organisations, space agencies, and scientific organisations play a crucial role to address this point. This goes through the understanding of what national space agencies like NASA or the European Space Agency (ESA) are undertaking in partnership with UNOOSA IAWAN and SMPG. Chapter 6 (Victoria P Andrew, Doris Daou and Lindley N Johnson) details the United State’s strategy and action plan concerning the detection of NEOs. Chapter 7 (Detlef Koschny) explains the ESA’s planetary defence programmes and the role of its ‘Planetary Defence Office’, especially informing the international community on the current and future position of NEOs, assessing the consequences of impacts and developing methods of deflection. The relevant parties involved play a significant role to observe, detect, track near-Earth asteroids and comets. Chapter 8 (Brent W Barbee) focuses on the various programmes and activities developed by various nations, such as Canada, Japan, France, China, and Luxembourg, as more and more asteroids and comets have been discovered, entirely changing our view of the Solar System, especially due to technological innovation. Furthermore, beyond the threat that NEOs represent, it should also take into account that governments, agencies, and industries could carry out space mining activity on celestial bodies in the near future.¹⁰ The extraction of space natural resources and sample return missions for economic interests is a possibility, and asteroids and comets are part of the scenario. With this in mind, constant monitoring of the sky and NEOs remain particularly important for societal and future economic activities that could be conducted on celestial bodies.

The second part of the book is titled ‘Legal Analysis of Different Aspects of Planetary Defence’ and deals with the legal issues connected to NEOs deflection missions. Chapter 9 (Steven Freeland) provides the main elements to understand the fundamental legal principles governing outer space activities embraced in the 1967 Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and other Celestial Bodies (OST). These are: (i) freedom of use and exploration (art. I of the OST); (ii) non-appropriation by claim of national sovereignty in outer space, including the Moon and other celestial bodies (art. II of the OST); (iii) application of general international law (art. III of the OST); (iv) forbidden to put in orbit around the Earth weapons of mass destruction and the Moon and other celestial bodies have to be used exclusively for peaceful purposes (art. IV of the OST); (v) international responsibility of States for national activities (art. VI of the OST); (vi) the international liability of the launching State in case of damage caused by its space objects (art. VII of the OST); (vii) international cooperation and mutual assistance (art. IX of the OST). The current legal regime on outer space was developed during the Cold War and is composed of hard law and soft law instruments that also apply to planetary defence missions. The author concludes that it is important to identify the proper aspects of a regulatory framework in order to protect humankind from NEOs threats while avoiding a further militarisation and weaponisation of outer space. Indeed, as stressed in Chapter 14 (Setsuko Aoki) there is a necessity to develop specific legal rules dealing with NEOs and military uses of outer space in particular in the case of deflection missions, and use of force against asteroids and comets. With this in mind, it is noted that it seems more appropriate to develop planetary defence rules from international environmental law and disaster law perspectives than from the legal framework related to the “use of force” (according to the UN Charter). This is due to the ambiguity on the terms ‘force’, ‘peaceful use’, ‘peaceful purposes’ on the Moon and celestial bodies as mentioned in Article IV (2) of the OST. In any case, as illustrated in chapters 15 and 16 (respectively by David A Koplow and Jack M Beard) the “use of force” against NEOs should be clarified and clearly addressed in a new legal framework to enhance transparency and confidence-building measures among States, due to the risks of tensions and mistrusts at international level in particular in the use of nuclear weapons in asteroid mitigation programmes.¹¹ Chapter 10 (Frans von der Dunk) illustrates the importance of publicly disseminating information to the international community in order to take action in the event of NEOs risk. The chapter highlights some significant topics that are then encompassed in the book. As the author mentions, ‘problems arise in terms of application of existing international law to solve the potentially dangerous (…) threats NEOs could come to pose’ (p. 135). Chapter 11 (Line Drube) underlines the importance of the work of academics and scientific bodies, such as the SMPAC Ad-hoc Working Group on Legal Issues to identify norms applicable in the realisation of planetary defence projects. The author emphasises also the necessity to set up additional standards taking into consideration the urgency of the situation (p. 148). Moreover, an appropriate and adequate legal framework in the field of NEOs is necessary by taking into account principles and customary international law, as well as national law. Chapter 12 (Irmgard Marboe) considers the sharing of information, the collection of data, and the principle of cooperation about potential NEOs which represent a notable task for governments, space agencies and private entities involved in planetary defence programmes. The United Nations space treaties contain some relevant provisions concerning the principle of due regard, the duty of cooperation and consultation, in particular arts. IX, X and XI of the OST. Furthermore, if a NEOs crash is primarily considered a potential disaster, it is important to take into account the 2016 ILC Draft Articles on the ‘Protection of persons in the event of disasters’ as NEOs can be regarded as a threat to human life and human rights so existing international principles and treaties in these fields are applicable, including international human rights law. There is therefore consideration of humanity, to save human life, and a responsibility to protect. So, the existence of ‘human rights’ considerations sees the application of various international treaties in the field as also mentioned in Chapter 13. Chapter 13 (Cordula Steinkogler) refers to whether a State is obliged under international law to undertake planetary defence measures in order to prevent or mitigate potential NEOs threats. With this in mind, international environmental law has to be considered, in particular the Principle 21 of the Stockholm Declaration and Principle 2 of the Rio Declaration stressing that States have to ensure that activities under their jurisdiction do not cause damage to the environment of other States or areas beyond the limits of national jurisdiction (p. 180). Furthermore, the 2001 ILC Articles on the ‘Prevention of Transboundary Harm from Hazardous Activities’ are relevant in case of NEOs threat as they deal with obligations related to consultation, prevention and diligent control in case of activities which risk causing transboundary harm. In addition, NEOs’ danger has to be evaluated under international disaster law in particular with respect to the obligation for States to reduce the risk that a disaster occurs by adopting proper actions (p. 200). Moreover, in case of extreme circumstances going beyond the affected State’s capacity to respond, it can look for assistance from an assisting State in terms of relief personnel, equipment, goods and services (p. 204).

Furthermore, another key legal issue related to NEOs threat regards the attribution of responsibility (e.g. States; organs of the State; private entities in case of space activities), and the State’s responsibility in case of the violation of an international obligation, (e.g. fails to share information about NEOs threat) which may see the application of the 2001 ILC Articles on the International Responsibility of States for Internationally Wrongful Acts. The issue of responsibility is addressed in Chapter 20 (Sergio Marchisio). The author notes that under international space law, according to art. VI of the OST, States bear responsibility for national space activities they have authorised, irrespective of whether they are carried out by governmental agencies or non-governmental entities. Lastly, in terms of responsibility, under general international law, there are some circumstances that preclude the wrongfulness of an act, such as consent, self-defence, force majeure, distress, and necessity. These actions are relevant in the case of planetary defence programmes to justify missions that will not be in compliance with international law in “normal” situations. Chapter 21 (Peter Stubbe) further details the role of private entities and non-state actors in the future mission of planetary defence, and the legal issues that this involvement raises under national and international law.

In addition, planetary defence programmes require considering the international legal framework for State liability established by art. VII of the OST and the 1972 Convention on International Liability for Damage Caused by Space Objects (‘Liability Convention’). However, there is no antecedent in practice. There are two regimes of liability under the space law regime: (1) a launching State is absolutely liable to pay compensation for damage caused by its space object on the surface of the Earth or to aircraft flight (art. II LIAB); (2) a launching State is liable if the damage, caused elsewhere than on the surface of the Earth, is due to its fault or the fault of persons for whom it is responsible (art. III LIAB). Consequently, the launching State is liable. As mentioned in Chapters 18 and 19 (respectively by Alexander Soucek and Henry Hertzfeld) it is needed to rethink the notion of launching in the context of planetary defence given the fact that the mission will be conducted most probably by a group of States; and that some States might take part to the programme but without being considered as launching State. Hence, it is important to foresee the scenarios of liability and damage in case of planetary defence, as well as contractual provisions between the parties involved, in particular insurance in case of failure of the mission, force majeure and cross-waiver of liability clauses which are now common clauses in space industry practice.¹² Nevertheless, as underlined by the authors, some issues remain in particular on the notion of launching State and dispute settlement in case of an accident on a territory of a State not involved in the mission. Another important point highlighted in Chapter 17 (Alissa J. Haddaji) is the “social aspect” of NEOs threat, in particular considering the probability of a catastrophe occurring and causing a considerable societal impact with population displacements and economic damage. The author makes a clear distinction between planetary defence from planetary protection. Planetary defence is the scientific field focusing on NEOs that represent potential threats to Earth, while planetary protection specifies the measures to prevent the contamination between Earth and other celestial bodies in space exploration missions. Then, she indicates that there are most likely lessons learnt from disasters on Earth in order to prepare the community to improve their preparedness plans in case of NEOs threats. Lastly, international cooperation and the UNGA, the UNSC, UNCOPUOS, SMPG and IAWN have an outstanding role in planetary defence missions according to their competencies, method of work, members, and decision-making (Chapter 22, Olavo de Oliveira Bittencourt).

Overall, the volume raises meaningful questions related to NEOs’ threats. It provides a variety of perspectives and topics addressed that give critical thoughts and adequate recommendations for deflection missions. The book underscores some pivotal elements to consider in the field of planetary defence in order to mitigate the effects of NEOs impacts, such as enhancing public awareness, improving the collection and sharing of scientific data, as well as strengthening the efficiency of cooperation between all actors involved, as States, space agencies, and private entities. Furthermore, the authors highlight the fact that it is necessary to rethink and adapt the current legal framework applicable to the outer space by taking into particular account the notion of launching State conducting planetary defence missions, the liability regime, the notion of damage; the economic, social and financial aspects of NEOs programme, by taking into consideration the diversity of NEOs and the choice of deflection method (e.g. use of nuclear technology). Authors offer multiple pathways forwards addressing diverse and important topics in the field of NEOs risks which present significant interest notably for legal researchers. Some further discussions would have been valuable, including perhaps a description of a plausible scenario detailing various steps of cooperation between public and private actors conducting such a mission. The potential content of a future agreement could have been interesting to explore, especially in terms of how its legal provisions would address the conduct of the parties involved, both in cases where civil and military entities are engaged in the mission, or when the mission is to be carried out by military personnel only.