The second phase of the Mars500 simulated mission to the Red Planet launched this on June 3, 2010, as six men -- a Frenchman, an Italian, one Chinese man and three Russians -- were locked inside a 19,500-cubic-foot facility outside of Moscow, where they will remain for the next 520 days.
The crew will remain completely isolated for that duration, going through the motions of a real manned mission to the Martian surface, including a 250 day journey just to get there, 30 days in orbit around mars, and 240 days for the return trip. During the 30 days in orbit around Mars, three of the crew members will "descend" to the surface in a landing module and two will actually conduct a spacewalk on a reconstructed Martian surface.
That's not to say the crew be totally cut off from their home planet. They will have access to email, though communications will be delayed by up to 40 minutes, just as they would be if the facility were humming through space millions of miles away.