As travel to Mars becomes closer to reality, new research is exploring the risks associated with the deep space journey.
The first study on how exposure to deep space radiation could impact the human body during a mission to Mars shows that there could be an increased risk of leukemia.
The study, published in the journal Leukemia, was conducted by researchers at Wake Forest Institute for Regenerative Medicine with funding from NASA.
Senior researcher Christopher Porada told CBC News that the impact of deep space radiation isn't something the scientific community knows a lot about.
To date, research on how space travel impacts human physiology has focused on the effects of zero gravity, he said.
"Astronauts would be exposed for a long period of time to these new types of radiation that we don't know what the effects may be," said Porada, who's also an associate professor of regenerative medicine.
Porada's team looked at the combined effects of two kinds of radiation in deep space, solar energetic particles — which are also a factor in space travel closer to earth — and galactic cosmic ray radiation, found in deep space.
Cosmic radiation is made up of heavy metal nuclei that contain relatively low levels of radiation but have extremely high energy particles, he said. This increases the radiation risk because those high-energy particles release more radiation than the ones used in X-rays.
"The energy [in the particles] is so high there isn't type of shielding that could can be put on the ship that could protect astronauts from radiation."
Another challenge is that the protection in place for solar radiation, especially aluminum, can increase exposure to cosmic radiation, Porada said. Parts of the hull designed to protect it and the astronauts from the effects of the sun act as a kind of conductor for the cosmic radiation.
In order to test how a human would respond to deep space radiation, Porada's team calculated the total radiation expected from a 400-day round-trip to Mars and used a particle accelerator at NASA to create a beam of radiation and expose human stem cells to the simulated radiation, he said.
Once exposed to radiation, the stem cells were implanted into mice so researchers could track the effects.
Porada is quick to point out that instead of the stem cells being exposed to radiation over a months-long journey to Mars, they received the radiation in the span of a few minutes.
"It's certainly more damaging in the short run to give a huge blast of radiation in a small time period," Porada said. "Some studies suggest if you take the same dose protracted over a long period of time more of the cells may survive, but may have mutations."
Another possible difference in the outcome is when the human cells are exposed to radiation. In Porada's research, human stem cells received radiation and were then put into mice. Similar research at Columbia University found that human stem cells implanted into the mice prior to radiation exposure didn't develop leukemia.
"We are having an ongoing dialogue to try to figure out what may be causing the differences between the results," Porada said.
One of the next steps in research on deep space radiation will be how to mitigate the risks, he said.
Research is already underway to test how dietary supplements could help protect astronauts from the radiation, Porada said.
There is also research into creating protection for a space craft that mimicks the earth's magnetosphere so astronauts aren't exposed to the radiation while in transit to Mars.
"[It's about] knowing that there may be a risk, but finding ways to get around this risk so the mission can go ahead," Porada said.