Thinking Ahead NASA hopes to put people on Mars within the next several decades. Because of the different orbits of Earth and Mars, the window of opportunity for travel between the two planets occurs only once every two years. That means that anyone traveling to Mars would have to stay there for a long time. The prospect of an extended stay on Mars prompts a number of concerns, among them the health effects of galactic cosmic radiation, found nearly everywhere in space. The magnetic field surrounding the Earth deflects the radiation, but Mars does not have such a field.
Radiation can cause illness or even death, depending on the dosage and length of exposure.
Therefore, astronauts will need a material they can use to build shelters and laboratories that also will shield against radiation. The lighter the material is in terms of mass, the better its shielding properties, and research has shown that liquid hydrogen is the best possible shield, Kiefer said. So the next best thing is a solid polymer, or chemical compound, that contains a lot of hydrogen. Obviously, Mars topsoil isn't easy to get on Earth. Chemical analysis of soil samples obtained by probes has shown that Mars topsoil is similar to that on the moon.