11. Higher Radiation Than the ISS
The International Space Station (ISS) orbits within Earth’s magnetic field, providing significant radiation protection for astronauts. On Mars, exposure is much greater—about 2.5 times higher than on the ISS, according to ESA’s ISS radiation research. This stark contrast underscores how leaving Earth’s natural shields behind elevates the risks, demanding much more robust countermeasures for Martian exploration.