Lunar exploration during the 20th century sought to reach, explore and, in some cases, return from the Moon,; rather than to serve as successive stages in the construction of permanent lunar infrastructure. Today, lunar missions are mostly about establishing the long-term infrastructure necessary to remain there. Under the Artemis Programme, NASA is developing phased infrastructure for long-term operations and an enduring human presence near the lunar south pole. The International Lunar Research Station (ILRS), led by China, is envisaged as an expandable facility capable of long-term robotic operation and shorter periods of human participation. Commercial entities are already involved in lunar delivery and landing services, while prospective activities extend to communications, mobility, power supply, prospecting and the use of lunar resources.
For sustained operational presence anywhere, power is a common dependency. This is certainly the case for the Moon, and nuclear power is one alternative. In January 2026, NASA and the US Department of Energy announced that they would work towards deploying such a fission surface power system by 2030. NASA now describes “Lunar Reactor-1” as a reactor intended to land on the Moon in that year. Nuclear surface power is therefore becoming part of near-term planning for sustained lunar operations.
These developments form part of a broader and increasingly global debate over lunar governance. Among the legal questions raised is the liability regime that would apply if a nuclear incident occurred on the lunar surface, but the interaction between the international space law liability framework and the civil liability regimes developed for nuclear installations has yet to receive any scholarly and policy attention. Can a state be held liable for a nuclear incident occurring on the face of the Moon under international law? The blog post will argue that instruments available under international law, while entirely relevant, fall short of providing a conclusive answer to the question. It will also suggest a tentative model for the way forward.
The International Legal Framework
Assume that State A is operating a nuclear reactor on the Moon. An accident damages a nearby rover and injures its occupants, while radioactive material ultimately causes damage on Earth. Can State A be held liable for these consequences?
Within international space law, the instruments to address this question would be the 1967 Outer Space Treaty (OST); and the 1972 Liability Convention. Less obvious, yet potentially relevant instruments include the 1963 Vienna Convention on Civil Liability for Nuclear Damage, as amended by the 1997 Protocol (the Vienna Convention); and the 1960 Convention on Third Party Liability in the Field of Nuclear Energy (the Paris Convention).
Article VI of the OST makes State A internationally responsible for its national activities, including those conducted by private entities, while Article VII and the Liability Convention address liability for damage caused by space objects. Damage on Earth engages Article II of the Liability Convention, as a launching State is absolutely liable for damage caused by its space object on the Earth’s surface or to aircrafts in flight. By contrast, Article III of the Liability Convention applies where damage occurs to a space object or to persons or property aboard it (as opposed to the surface of the Earth). Liability under Article III depends upon the fault of the launching State or of persons for whom it is responsible. The same reactor failure may therefore attract absolute liability for its terrestrial consequences but fault-based liability for damage to equipment on or around the Moon.
Nuclear risk exposes the limitations of this framework. Establishing fault may be difficult where decisions concerning a reactor involve public and private actors across several jurisdictions. The Liability Convention also operates through an inter-State claims process and does not provide injured non-state parties with a direct international cause of action. It also does not channel claims towards the nuclear operator or require financial security sufficient to compensate those affected.
Contamination as Damage
The relatively complex case here is not an explosion that destroys a rover, but, for example, a leak that leaves it physically intact while making the surrounding area unsafe. Such contamination may force operations to cease, render equipment inaccessible and produce health aeffects years later, as is often the case with terrestrial nuclear accidents. The Liability Convention defines “damage” to include loss of life, personal injury or impairment of health, and loss of or damage to property. This could accommodate radiation injuries, but it is less clear whether it extends to loss of use, remediation costs, economic loss or contamination of the lunar environment where no person or property has suffered physical damage. Its claims timetable is also poorly adapted to latent injury.
International nuclear liability law addresses these problems more directly. The Vienna and Paris regimes recognize broader categories of nuclear damage and, subject to their respective conditions, provide for strict operator liability, channelling of liability and mandatory financial security. This tailored treatment of nuclear harm prompts the following question: If the characteristics of nuclear risk justify a specialised civil liability regime on Earth, why should moving the reactor to the Moon restore fault as the principal standard and leave contamination at the margins of compensable damage?
Can International Law on Nuclear Liability Travel to the Moon?
The nuclear liability conventions are prima facie terrestrial instruments. Neither expressly addresses installations or damage on celestial bodies. The geographical scope of the Paris Convention also largely supports this reading. Article 2(a) principally covers damage suffered in the territory or in any maritime zones of specified States, or on board their registered ships and aircraft. Although Article 13 contemplates nuclear incidents occurring outside the territories of Contracting Parties, it assigns jurisdiction to the courts of the State in whose territory the liable operator’s installation is situated. The Convention therefore provides no obvious jurisdictional connection where the installation itself is located on the Moon.
The Vienna Convention warrants closer scrutiny. Article I(1)(d) defines the “Installation State” as the Contracting Party in whose territory the installation is situated or, where it “is not situated within the territory of any State”, the Contracting Party by which or under whose authority it is operated. Article I(1)(j)(i) defines a “nuclear installation” to include any nuclear reactor other than one equipping a means of sea or air transport. Article XI(2) further provides that, where an incident occurs outside the territory of any Contracting Party or outside an area notified under Article XI(1 bis), jurisdiction lies with the courts of the Installation State. Nothing in these provisions expressly confines the installation itself to Earth.
This suggests that the Vienna Convention is not necessarily confined to terrestrial installations. A lunar installation cannot be situated within national territory, since Article II of the Outer Space Treaty prohibits national appropriation of the Moon. However, the absence of territorial sovereignty does not entail an absence of jurisdiction. Under Article VIII of the Outer Space Treaty, the State of registry retains jurisdiction and control over a registered space object. A lunar reactor operated by or under the authority of a Contracting Party therefore bears a clear resemblance to the extraterritorial installation contemplated by Article I(1)(d).
This does not establish Vienna’s direct applicability. Its definitions, scope, jurisdictional provisions and domestic implementation would have to be read together, as must its relationship with space law. Participation is also crucial: notably, the United States, whose project supplies the immediate policy context, is not a party to either Vienna or Paris Conventions. The narrower conclusion is nevertheless important: the Vienna Convention’s relevance should not be dismissed. Its text appears capable of addressing relevant and consequential jurisdictional questions, even if it does not conclusively answer themit.
Terrestrial Nuclear Liability as a Model
Direct application of these instruments is only one (even ifyet admittedly important) part of our inquiry. Terrestrial nuclear liability law may be more valuable as a model for a new framework tailored to lunar nuclear installations. Such a regime could preserve State responsibility under Article VI OST and launching State liability under the Liability Convention while adding a civil liability layer based on strict liability for defined nuclear damage. This is also a valuable opportunity to assess whether and under what circumstances contamination could amount to damage and establish an ex ante framework for reasonable preventive and remediation measures. Another pressing issue is whether space law can accommodate economic loss and latent health effects as damage.
As is often the case in space law, national authorization regimes are an important starting point for implementation. Article VI requires States to authorise and continuously supervise non-governmental space activities. A licence for a privately operated lunar reactor could therefore require appropriate operator liability, insurance or other financial security, emergency planning and arrangements for decommissioning and spent fuel. Whatever the ownership model may be, resources for responding to an accident should exist before the reactor is activated.
The existing UN Principles on Nuclear Power Sources and the 2009 UN–IAEA Safety Framework provide important safety guidance, but they do not create a detailed governance framework or a compensation regime. The development of lunar nuclear power should be accompanied by an equally serious effort to identify the applicable liability architecture embedded within a robust, comprehensive lunar governance framework. Once a reactor is operating on the Moon, uncertainty over fault, compensable damage, competent fora and available financial resources will be immediate realities. The legal framework should be developed alongside the technology and not in response to its first, potentially catastrophic, failure.
