I think it depends how far you are going for something like exploring another solar system uncrewed would be the way to go atleast until the future just have computers do it however for the matter of our solar system crewed are definitely the way to go.
Radiation on Mars:
Clearly, the high level of radiation on Mars will present many problems for future manned missions, but radiation-contaminated water is not one of them.
The type of radiation present on Mars is not due to any radioactive materials present on the Red Planet, but is due to regular exposure to cosmic rays and solar wind, plus it receives occasional lethal blasts that occur with strong solar flares.
Contamination versus Exposure:
However, a body of water exposed to radiation is not necessarily contaminated with radioactive material.
For water to be contaminated, radioactive material must be present; either floating on or dissolved in the water. Since cosmic and solar radiation is delivered in the form of rays, it simply passes through the water and does not contaminate it or make the water radioactive.