Extraterrestrial real estate refers to claims of land ownership on other planets, natural satellites, or parts of space by certain organizations or individuals. Previous claims are not recognized by any authority, and have no legal standing. Nevertheless, some private individuals and organizations have claimed ownership of celestial bodies, such as the Moon, and are actively involved in "selling" parts of them through certificates of ownership termed "Lunar deeds", "Martian deeds" or similar.
While personal claims have little weight, whole countries could potentially lay claim to colonizing certain bodies. Extraterrestrial Real Estate not only deals with the legal standpoints of potential colonization, but how it could be feasible for long-term real estate. There are multiple factors to consider in using another planet for real estate including how to create a real estate market, transportation, planetary protection, astrobiology, sustainability, and the orbital real estate of the planet, as well.
The topic of real estate on celestial objects has been present since the 1890s. Dean Lindsay made claims for all extraterrestrial objects on June 15, 1936. The public sent offers to buy objects from him as well.
The United Nations sponsored 1967 Outer Space Treaty established all of outer space as an international commons by describing it as the "province of all mankind" and forbidding all the nations from claiming territorial sovereignty. Article VI vests the responsibility for activities in space to States Parties, regardless of whether they are carried out by governments or non-governmental entities. The Outer Space Treaty of 1967 had been ratified by 102 countries by 2013, including all the major space-faring nations. It has also been signed but not yet ratified by 26 other nations.
The Outer Space Treaty established the basic ramifications for space activity in Article 1: "The exploration and use of outer space, including the Moon and other celestial bodies, shall be carried out for the benefit and in the interests of all countries, irrespective of their degree of economic or scientific development, and shall be the province of all mankind."
It continues in Article 2 by stating:
The development of international space law has revolved much around outer space being defined as the "province of all mankind". The Magna Carta of Space presented by William A. Hyman in 1966 framed outer space explicitly not as terra nullius but as res communis, which subsequently influenced the work of the United Nations Committee on the Peaceful Uses of Outer Space.
A subsequent treaty document, the international Moon Treaty--finalised in 1979 (just five countries had ratified it by 1984, but five countries was sufficient for it to be considered officially in force)--went further and forbade private ownership of extraterrestrial real estate. This agreement has not been widely ratified, with only 18 countries having ratified it by 2018.
Several individuals and private organizations claimed ownership of the moon and other extraterrestrial bodies, but no such claims have yet been recognized. A white paper by the Competitive Enterprise Institute suggested legislation whereby the US would recognize claims made by private entities, American and others, which meet certain conditions regarding habitation and transportation.
A number of individuals and organizations offer schemes or plans claiming to allow people to purchase portions of the Moon or other celestial bodies. Though the details of some of the schemes' legal arguments vary, one goes so far as to state that although the Outer Space Treaty, which entered force in 1967, forbids countries from claiming celestial bodies, there is no such provision forbidding private individuals from doing so. However, Article VI of this treaty states "The activities of non-governmental entities in outer space, including the moon and other celestial bodies, shall require authorization and continuing supervision by the appropriate State Party to the Treaty." Thus, while it does not explicitly prohibit such schemes, the treaty does require they be authorized by the schemers' government.
The short story The Man Who Sold the Moon by Robert A. Heinlein, which was written in 1949, offers a portrayal regarding such plans or schemes, and created the concept of a Lunar Republic. Heinlein's Stranger in a Strange Land also makes reference to a space law case called the Larkin Decision.
A space ownership issue of current practical importance is the allocation of slots for satellites in geostationary orbit. This is managed by the International Telecommunication Union. The 1976 Declaration of the First Meeting of Equatorial Countries, also known as the Bogota Declaration, signed by several countries located on the Earth's equator, attempted to assert sovereignty over those portions of the geostationary orbit that continuously lie over the signatory nation's territory. These claims did not receive wider international support or recognition and were subsequently largely abandoned.
Two problematic issues arise regarding derelict spacecraft: In orbit around the Earth, 'dead' and abandoned satellites threaten future travel in the same orbits with a spray of deadly debris. In orbit around extraterrestrial planets, non-sterile orbiters in decaying orbits treaten to pollute the remote planets they orbit with Earth-organisms, and hence create a false 'signal' of alien life, possibly destroying or supplanting native life, or infesting its remains.
A prominent environmental problem in near-Earth orbital space is 'space junk'. Human-made refuse left in space endangers prime orbital 'real estate' for future satellites, causing big problems for future use of nearby space. In the case of debris cluttering orbital space, if the orbiting debris continue to build up without remediation, orbits near the earth will become so crowded with deadly missiles that some operations in space will no longer be attainable.
To remediate the damage already done by human-made objects, astronauts will need to bring specific hardware into space to exterminate the debris. Once cleared, the surrounding space around a planet can then be used for more real estate opportunities. There are specific orbits, however, that have caused ownership debate.
Another issue is the crashing of abandoned orbital derbies on extraterrestrial planets. Before the 21st century, exploration of other planets in the Solar system raised little concern about contaminating planets with life from the Earth. Since then experiments have shown that some terrestrial life is astonishingly hardy, and the time spent in transit in space is not a guarantee of a sterile spacecraft on arrival. Some 'bugs' will survive the trip, potentially invade the planet, elinating the chance of determining whether life arose independently on other planets, or in the deep geologic past has spread between the planets of the Solar system via the hypothetical "panspermia" processes. If an old, contaminated orbiter crashes onto an extraterrestrial planet, except in extreme cases, it will no longer be possible to test the panspermia hypothesis with any confidence in the outcome.