The Mars500 project is about to start its next phase. They will be simulating a complete 18-month mission to Mars here on earth. The crew of six will be totally isolated in a simulator for the entire time. You can see an illustration of the simulator modules in this article:

Newlywed astronaut puts honeymoon on hold as he begins 18-month simulated Mars mission

The European Space Agency experiment, called Mars500, is designed to test how humans would cope during a 520-day mission to the Red Planet, with a 250-day outward trip, a 30-day stay on its surface, and a 240-day return flight.

Next week Sitev will be sealed into four windowless metal compartments, which will not be opened until the end of the simulated mission.

It means that all food and water supplies and other pieces of equipment will need to loaded before the door is bolted.

During nearly two years of isolation, the crew members – three Russians, a Chinese, a Frenchman and an Italian – will experience many of the conditions likely to be encountered by astronauts on a real space flight, except for radiation and weightlessness.

The following video provides an excellent overview of the mission along with shots of the simulator’s interior:

Much of the simulation will be run in just a part of the simulator, representing the trips out to Mars and back. For the 30-day portion simulating the actual time on Mars, the full simulator will be available to the crew.

In the United States, there is the Mars Desert Research Station, as described here:

You can see that this effort lacks a lot of the rigor found in the Mars500 simulation.

See also:
- How did they film the moon landing?
- How a Mars Mission will work, according to NASA
- why is it so hard to put men and women on Mars?