"Playing Mars"

An international trio of volunteers has simulated a Mars landing in Moscow, walking on a sandbox surface like the ones engineers use to prepare rovers for the real thing.
Russia's Alexandr Smoleevskiy, Diego Urbina of Italy and Wang Yue of China "landed" on the Red Planet mockup at the Institute of Biomedical Problems on Valentine's Day, as part of the Mars500 project. There's an earlier blog on the subject below. Here Urbina (left) and Smoleevskiy take their first steps on "Mars."

ESA/IBMP
The team is learning valuable lessons about what it will take to live and work in space on a real mission to Mars. The only problem is they aren't in space. Everything they do -- in the simulated main vehicle, the simulated lander and on the simulated surface, takes place in 1 g, a doorway away from Earth.
Now NASA is considering adding a little more realism to the mix on the International Space Station. Engineers are studying what it would take to to use volume on the ISS to do in Earth orbit pretty much what the Mars500 volunteers are doing on the ground - simulate a trip to Mars.

NASA
Details aren't available yet, but astronaut John Grunsfeld -- a member of the NASA Advisory Council with extensive spacewalking experience at the Hubble Space Telescope -- has some ideas. At a recent NAC meeting he suggested isolating a couple of station crew members in a module for six months to simulate a transit to Mars.
The primary analog to a real Mars mission would be weightlessness, and the hazards of the low Earth orbit environment. Additional realism could be added with delayed communications, perhaps limited to text, to simulate growing distance from a Mars mission control center on Earth.
If something breaks inside the simulated Mars ship, the crew would have to fix it or do without (within reason, of course - there still would be help on the other side of the hatch). And they would have to exercise to offset the effects of microgravity on their bodies, in preparation for the simulation's second phase -- what Grunsfeld calls "playing Mars."
Once the two Mars crewmen return to Earth, they would be whisked to a nearby Martian-surface mockup to continue the simulation. There would be air to breathe, and gravity, but it still would provide valuable data on how humans perform at exploration tasks after prolonged spaceflight.
For the next few years the only way down from the station for a mock Mars crew will be on Russia's Soyuz vehicle, which lands on the steppe of Kazakhstan. So if Grunsfeld has his way, don't be surprised if the simulated "Martians" turn out to be camels.

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