If humans immigrate to Mars, why can they only survive for 60 days?

National Aeronautics and Space Administration (NASA) previously reported that humans can only survive for about 60 days if they want to immigrate to Mars. According to the data detected by Mars-1, the living environment on Mars is not suitable for human habitation at present, and at least several difficulties must be overcome.

If we really want to start the era of moving to Mars, then oxygen is a problem that cannot be ignored. The photosynthesis of plants on the earth produces oxygen, which can not meet the needs of human survival on Mars, but oxygen can also be made from chemicals according to chemical reactions, but the raw materials that can bring rockets are very limited, so the oxygen problem is a great difficulty. Secondly, at present, there is not a large amount of water resources found on Mars, and oxygen and water are also a major reason that hinders human beings from staying on Mars. The maximum amount of oxygen and water available for human survival is about 60 days.