Ultimately, the twins study gives NASA a catalog of things to monitor on future missions to see if other astronauts react the same way. Astronauts on future missions will be able to do some of this testing in space instead of freezing samples for scientists back home, Mason said.
Immune issues sound familiar to Dr. Jerry Linenger, an American astronaut who spent more than four months on the Russian space station Mir. He said he was never sick in orbit, but once he came back to Earth “I was probably more sick than I was in my life.”
Astronauts launch into orbit with their own germs and get exposed to their crewmates’ germs and then after a week with nothing else new in the “very sterile environment” of a space station “your immune system is really not challenged,” Linenger said.
A human mission to Mars, which NASA hopes to launch in the 2030s, will take 30 months, including time on the surface, Kundrot said.
Radiation is a top concern. The mission would expose astronauts to galactic cosmic radiation levels higher than NASA’s own safety standard. It’s “just a little bit over,” he said.
On Earth and even on the space station, Earth’s magnetic field shields astronauts from lots of radiation. There would be no such shielding on the way to Mars and back, but tunnels or dirt-covered habitats could help a bit on Mars, Kundrot said
Kelly, who turns 55 next week, said he’d go to Mars. He said a trip that long “wouldn’t be worse than what I experienced. Possibly better. I think the big physical challenge, radiation aside, will be a mission where you are in space for years.”