Currency exchange company Travelex recently teamed up with the University of Leicester's National Space Centre to create a prototype currency for future space travellers.
Called QUIDs (Quasi Universal Intergalactic Denomination), the coins are constructed of "space qualified" polytetrafluoroethylene (Teflon) and rounded to prevent damage to space suits. Travelex claimed QUID's exchange rate at 8.68 Euros per, though it's not recognized as a legitimate currency by anyone.
While more science fiction than realistic, the currency raises some practical questions, particularly in light of the burgeoning space tourism industry. Can our current fixation on digital commerce work it situations where it's impractical to send transactions over millions or billions of miles? And with magnetic data vulnerable to rays, you might want to leave your debit card planetside. Who knows, maybe cash is the way to go?