What is the Outer Space Treaty?

The Outer Space Treaty is an international agreement that governs how nations act in space. Formally known as the "Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies," it is one of international space law’s foundational documents.

The overall purpose of the Outer Space Treaty is to keep space peaceful. Key provisions include banning nuclear weapons in space, preventing any country from claiming sovereignty over any celestial body, and establishing that space is to be freely explored and used by all nations for peaceful purposes.

The origin of the Outer Space Treaty

The Outer Space Treaty was motivated by concerns over the use of nuclear weapons in space. During the Cold War, the Soviet Union and the United States competed to develop powerful rockets and nuclear weapons, going so far as to test nuclear weapons in space. In response to this arms race, the United Nations began debating proposals for an arms control treaty governing outer space, which led to the development of the Outer Space Treaty. 

The treaty was adopted by the United Nations in 1967. Its first signatories were the United States, the United Kingdom, and the Soviet Union. As of 2024, 115 countries are parties to the treaty, including all major spacefaring nations. Another 22 countries are signatories.

Key principles of the Outer Space Treaty

The Outer Space Treaty includes several important principles that guide space exploration and use to this day. According to the U.N. Office of Outer Space Affairs, the treaty’s key principles are:

• That the exploration and use of outer space shall be carried out for the benefit and in the interests of all countries and shall be the province of all mankind;

• That outer space shall be free for exploration and use by all states;

• That outer space is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means;

• That states shall not place nuclear weapons or other weapons of mass destruction in orbit or on celestial bodies or station them in outer space in any other manner;

• That the Moon and other celestial bodies shall be used exclusively for peaceful purposes; prohibits their use for testing weapons of any kind, conducting military maneuvers, or establishing military bases, installations, and fortifications

• That astronauts shall be regarded as the envoys of mankind;

• That states shall be responsible for national space activities whether carried out by governmental or non-governmental entities;

• That states shall be liable for damage caused by their space objects; and

• That states shall avoid harmful contamination of space and celestial bodies.

Other space treaties

Space activities have evolved enormously since 1967. Still, like many foundational documents, the Outer Space Treaty continues to guide the way international space law addresses new challenges, such as the growth of commercial space activities, interest in mining celestial bodies, removing orbital debris, and more.

Several other treaties and agreements have built on the foundations laid by the Outer Space Treaty to address specific aspects of space activities and provide additional legal frameworks for outer space governance.

The Rescue Agreement (1968) details states’ obligations to assist astronauts in distress and to return them to their country of origin. It also requires states to return parts of spacecraft found within their territory to the launching country.

The Liability Convention (1972) elaborates on the mechanisms for damage compensation that states are liable for if their space activities cause harm to other states or their properties, whether in space or on Earth.

The Registration Convention (1975) requires states to provide the United Nations with a registry of objects launched into outer space, to help manage space traffic and mitigate space debris.

The Moon Agreement (1984) elaborates on the Outer Space Treaty’s principles regarding the Moon, specifically declaring that the Moon and its natural resources are the common heritage of mankind and can’t be exploited by any individual state or company for profit. However, the Moon Agreement has been ratified by relatively few countries and lacks participation from all major space-faring nations.

The Artemis Accords (2020): Unlike the above agreements, the Artemis Accords are not affiliated with the United Nations. Instead, they were developed by the United States in conjunction with NASA’s Artemis Program. The Artemis Accords are designed to serve as practical and modern principles to guide cooperation in space exploration. As of May 2024, 39 countries have signed the Artemis Accords.