their oxygen in the liquid state of matter in onboard tanks that keep the oxygen at cryogenic or super-cold temperatures to save space on the craft. The Russian space station MIR used special onboard generators to separate water into oxygen and hydrogen. On the Mercury, Gemini, and Apollo missions, the cabin atmosphere consisted of one hundred percent oxygen. This gave the cabin a pressure of 0.3 kg/sq cm (about 5 lbs/sq in). However, on the space shuttle and the MIR space station, the atmosphere is a mixture of oxygen and nitrogen to provide an atmospheric pressure of 1.01 kg/sq cm (14.5 lbs/sq in), which is slightly lower than that of sea level. Before an astronaut could go on space walks, astronauts and cosmonauts had to breathe pure oxygen to rid their bloodstreams of nitrogen. This eliminated the chance that the space walker would get decompression sickness because of the different pressures from the space suit and the cabin. Since the suit had a pressure of 0.30 kg/sq. cm, the sudden decompression would cause nitrogen bubbles to form in the bloodstream and other bodily organs and would result in a painful and potentially lethal condition. This atmospheric mixture is planned to be used in the International Space Station.A problem with micro gravity and weightlessness is that in long duration missions in this type of environment creates problems with the muscles weakening. In space, muscles do not have to exert much force to move and in turn get weaker. This creates a problem with a mission to Mars, the long duration in a weightless environment will weaken the muscles and when craft lands on Mars, the crew will have a difficult time adjusting to the new environment and completing their jobs. To make this problem less severe, scientist are working on a way to create artificial gravity. This will make the environment in which the astronauts travel in more like that of Earth, so when the crew lands on Mars, they will have...
