The astronauts who run a mission to Mars will be faced with many obstacles. Not only radiation, microbes can also be a big threat for the astronauts.
The scientists analyzed data from a 17-month experiment of spacecraft simulation conditions on missions to Mars. They found that a capsule filled with microscopic life could potentially harm the health of Martian astronauts.
Yes there is microbes also on the MIR space station that is eating the structure up. It's over a long period of time though.