Mars One aims to establish a permanent human settlement on Mars in 2023, requiring no return mission.
The absence of a return mission reduces the radiation exposure from galactic cosmic rays. These cosmic rays are hard to shield against without the use of a prohibitive shielding mass, which would require more than 10 times the standard spacecraft shielding. Reducing the time spent traveling through space — and, thus, the exposure from the cosmic rays — is significant, as these rays are the source of 95 percent of the radiation exposure, according to a recent paper published May 31 in the journal Science.