An astronaut takes many things into space, but a wallet isn't one of them. In humanity's relatively limited time in space, no new commercial infrastructure has emerged. What will be the currency of outer space? How will we regulate it? Who will prosecute the inevitable fraud? With multiple plans for the colonization of Mars already in the works, issues that once seemed abstract are becoming more pressing.

Legal minds have theorized — and science fiction has demonstrated — some answers to those questions. But aside from the occasional stunt, businesses have said little about the issue. PayPal, the payments division of eBay, aims to change that today with the announcement of PayPal Galactic. Together with the SETI Institute and the Space Tourism Society, PayPal is forming a working group dedicated to sketching out the future of money in the galaxy.

"What does space becoming a commercial reality actually look like?"

"This is us seeing a massive problem and saying hey, we're going to try to drive awareness and public interest around something that is going to be happening very, very quickly and which no one has prepared for yet," said Anuj Nayar, a PayPal spokesman. "And that's basically: what does space becoming a commercial reality actually look like?"

PayPal Galactic is equal parts task force, thought experiment, and marketing stunt, aimed at answering questions that are rapidly leaving the realm of the hypothetical. Virgin Galactic, Space X, and similar projects have brought space tourism wide, mainstream attention; several hundred people have made deposits to reserve a spot on a Virgin Galactic flight. Meanwhile, the Russian firm Orbital Technologies has announced plans to build a space hotel later this decade. And wherever people go, legal questions follow.

The foundation of space law lies in the Outer Space Treaty of 1967. The treaty provides a basic legal framework for galactic travel, stipulating that any country is free to explore outer space so long as it does so peacefully. Exploration is to "carried out for the benefit and in the interests of all countries," and they are prohibited from placing nuclear weapons or other weapons of mass destruction in orbit. No treaty to date has attempted to create a legal framework for commerce — but that day is coming, researchers say.

"It's actually getting quite tangible to think about what transactions are going to mean," said Jill Tarter, a founding member of SETI and a scientist who focuses on the search for extraterrestrial life. "How a starship, or a colony, or even just a mining crew in orbit around an asteroid — what is their monetary means of exchange? How do they have value?" As part of PayPal Galactic, the company is sponsoring a crowdfunding campaign to raise money for SETI and support its search for extraterrestrial life and planets outside our solar system.

For now, commerce in space works just as it does on the earth. While few transactions are made in orbit, astronauts do barter for smaller items, said Skip Smith, a director of the International Institute of Space Law and the former head of space law for the Air Force. When space tourism begins in earnest, tourists will likely pre-pay for goods and services while they are still on the ground, he said.

When space hotels begin accepting tourists, they will likely continue to support credit-card purchases. "Once you're up there, if you want to buy an extra bottle of champagne, they can probably run that on your charge card," Smith said. But longer stays in orbit, and the colonization of new planets, will make that more difficult. Eventually, he said — maybe 20 years from now — new solutions will need to emerge.

"Science fiction has become a reality."

PayPal, which will make its announcement today at SETI headquarters in Mountain View, hopes that solution will run through its servers. David Marcus, PayPal's president, will be joined by officials from SETI, the Space Tourism Society, and astronaut Buzz Aldrin. "The time has now come for us to start planning for the future; a future where we aren’t just talking about global payments," Marcus said in a statement. "What we once deemed to be science fiction has become a reality."

Figuring out payments in space will mean tackling three key areas, PayPal says: technology, business operations, and the regulatory and compliance framework. PayPal will focus on the technology. "That's where most of our expertise comes in," Najar said.

The technology problems around space money are significant. Getting online from space today is expensive. Long latency times between sending and receiving data create new possibilities for fraud. And for a company that already receives regular drubbings for its customer service, handling complaints filed in space promises to offer new public-relations challenges.

Still, someone will have to tackle questions like these eventually. "These questions are already relevant," Tarter said. Now it's up to PayPal to answer them.