The Mars Society recently sent seven people to Devon Island in the Canadian Arctic to simulate a martian colony. For four months they lived in a “tin can” habitat, wore space suits when venturing outside, and ate freeze-dried food. They could communicate with Earth, but there was the same time delay Mars colonists would experience. They also gained 39 minutes each day, since Mars has longer days than Earth. Participants conducted science experiments, but also were experiment subjects: their sleep patterns were studied, as was their water use. The overall experience must have been good because one of the participants, Kim Binsted of the University of Hawaii, enthusiastically said she would volunteer for a real Mars mission.
A trip to Mars, however, will not be like a trip to the moon. What goes to Mars will most probably stay there...
The riskiest parts of space travel are the take off and landing, and by not coming back to Earth you reduce your risk by half. You also reduce the amount of zero gravity you are exposed to during space travel, which has significant hazards for health. Mars is the second safest place in the solar system, said Davies, and lava tube caves would make a good protected habitat.
Mars' atmosphere is 95% carbon dioxide; Earth's is less than 0.05%. Meaning, the atmosphere on Mars is dead, and Earth's is life. I can't understand how any scientist can imagine a macroscopic animal or plant existing outside of life.