The Mars One project is looking to build a community on Mars in 2023.  Presumably the people of Mars would not be governed by a country on Earth and as the community thrives they will need their own currency as a medium of exchange.  Since Bitcoin is also not backed by governments of any country then surely this is the obvious choice of currency for the people of Mars.  

http://www.bbc.co.uk/news/science-environment-22146456