Planet solar wind around itself called the magnetosphere, which the wind cannot penetrate. The magnetosphere can be much larger than the planet itself. In contrast, non-magnetized planets have only small magnetospheres induced by interaction of the ionosphere with the solar wind, which cannot effectively protect the planet. Of the eight planets in the Solar System, only Venus and Mars lack such a magnetic field. In addition, the moon of Jupiter Ganymede also has one. Of the magnetized planets the magnetic field of Mercury is the weakest, and is barely able to deflect the solar wind. Ganymede's magnetic field is several times
Mars Radiation Environment Experiment be experienced by future astronauts and it helped determine possible effects of Martian radiation on human beings. Space radiation comes from cosmic rays emitted by our local star, the Sun, and from stars beyond the Solar System as well. Space radiation can trigger cancer and cause damage to the central nervous system. Similar instruments are flown on the Space Shuttles and on the International Space Station (ISS), but none have ever flown outside Earth's protective magnetosphere, which blocks much of this radiation from reaching the surface of our planet. In the autumn of 2003 after a series of particularly strong