Can anyone claim the red planet or natural resources on asteroids?
Business leaders and legal experts say the question has become more than philosophical as a growing number of firms, often backed by capital and technology from Silicon Valley, have set their sights on the resources of outer space asteroids and Mars.
In order to avoid conflicts between competing companies and countries over outer space resources, more work needs to be done on Earth to determine who owns commodities taken from celestial bodies, analysts said.
"There is a huge debate on whether companies can simply travel to space and extract its resources," said Barry Kellman, a law professor who studies space governance at DePaul University in Chicago.
"There is no way to answer the question until someone does it," Kellman said.
US-based Planetary Resources, a firm backed by Google founder Larry Page and Virgin Group's Richard Branson, expects to be mining asteroids for water in the next 10 to 15 years.
The company will launch its first robotic probe mission to scout asteroids for resource deposits in 2020, said Planetary Resources' Chief Executive Chris Lewicki.
"If you obtain a resource and bring it with you, it becomes your property," Lewicki said, citing recently passed space laws in the US and Luxembourg that offer a legal framework to ensure that private operators can be confident about their rights over resources they extract in space.
"You can sell, keep or deliver (space resources) peacefully," Lewicki added.
The firm plans to extract oxygen and hydrogen, the components of water, from asteroids to sell.
Lewicki is not planning on bringing those water resources back to Earth; he wants market them in space, creating a "gas station" for other exploration missions.
Hydrogen and oxygen, kept at a docking station orbiting around Earth, will be used to fuel other space ships.
Other analysts are not sure if companies can just fly up and start harvesting cosmic water, legally speaking.
The Outer Space Treaty of 1967 is the main international standard for what companies and countries are allowed to do when they aren't on earth, said Jacob Haqq-Misra, director of the Blue Marble Space Institute of Science, a Seattle-based research group.
The treaty says that space is the "provenance of all mankind". Countries cannot claim "national appropriation" or sovereignty over the Moon or other celestial bodies "by occupation or by other means", the treaty says.
This clause could prove tricky for private firms who want to mine on asteroids or Mars, said Haqq-Misra, including Planetary Resources and SpaceX, the private rocketship company run by tech billionaire Elon Musk.
While the 1967 treaty is considered the global standard for sharing space, individual countries have recently passed laws allowing for property rights in the great beyond.
Luxembourg this month brought into force laws allowing private firms to own resources extracted from outer space in a move hailed by the nascent space mining industry.
Planetary Resources, for example, maintains an office in the small European country better known for its finance industry than space exploration.
The US in 2015 introduced similar legislation for private space resource ownership but it only applies to firms majority owned by Americans.
From sea to space
Along with national legislation and the 1967 treaty, there are other earthly regulations which could provide guidance for managing extraterrestrial resources, legal experts said.
Under the United Nations' Law of the Sea Convention countries have exclusive rights to exploit natural resources within around 322km of their coast line, but ships and planes from other nations can freely pass through the waters.
This could serve as a template for space resource rights, where companies have exclusive economic rights in a given area around their landing point, but not ownership over an entire asteroid or planet, lawyers said.
"It's advantageous to work out a system where people can acquire property rights enforceable through a legal process," Andrew Brehm, an attorney with Scopelitis, Garvin, Light Hanson & Feary in Milwaukee.
"That being said, outer space is viewed in society as something similar to the ocean, where there is a collective interest," Brehm said.
"A first come, first serve system does not necessarily work well when only certain countries or private entities can (currently) reach outer space."