Astronauts exploring the solar system on a Mars mission might experience brain damage because of exposure to space radiation, a new study suggests.

If the results are confirmed by other research, they could have implications for the feasibility of NASA's planned Mars mission, set to take place sometime in the 2030s.

In the study, published Friday in the journal Science Advances, scientists bombarded mice with doses of charged particles that simulate those that astronauts would be exposed to on a trip to Mars. The researchers' goal was to see how the brains of the rodents changed afterward, and the results weren’t exactly heartening for future space explorers.

Charles Limoli, a radiation oncology professor at the University of California at Irvine, and his team of researchers found that the mice weren't as curious and became confused after they were blasted with radiation. The mouse brains were also physically altered by the radiation.

The researchers involved in the study concluded that astronauts' cumulative radiation exposure during a Mars mission, which would likely take up to three years, might have cause them to have difficulty focusing or performing certain tasks. The source of the particularly harmful radiation exposure isn't the Sun, but rather galactic cosmic rays — charged particles mostly sent out into the universe during the explosions of dying stars. (Radiation from the Sun can also be dangerous, but it is easier to protect astronauts from.)

“This is not positive news for astronauts deployed on a two- to three-year round trip to Mars,” Limoli said in a statement.

“Performance decrements, memory deficits, and loss of awareness and focus during spaceflight may affect mission-critical activities, and exposure to these particles may have long-term adverse consequences to cognition throughout life.”

Why does radiation matter?

Scientists have long been interested in understanding the ways that these galactic cosmic rays affect the human body.

“NASA recognizes the importance of understanding the effects of space radiation on humans during long-duration missions beyond Earth orbit, and these studies and future studies will continue to inform our understanding as we prepare for the journey to Mars,” NASA spokeswoman Stephanie Schierholz told Mashable via email.

NASA has instituted a threshold for the level of radiation an astronaut can be exposed to in his or her lifetime because of the elevated cancer risk that comes with radiation exposure. This limit complicates the agency’s mission to send humans to Mars by the 2030s. A two-to-three-year mission to the Red Planet would potentially expose astronauts to an amount of radiation well above the current amount allowed under NASA guidelines, according to earlier research that was conducted in part with the help of the Curiosity Mars rover.

Not so fast…

But the new study, which was part of NASA's Human Research Program, won't necessarily scrub a Mars mission.

Cosmic radiation experiments are notoriously hard to conduct because it’s very difficult to create the same conditions on Earth that an astronaut would experience in space during a Mars voyage. The mice in the new study were subjected to relatively high doses of radiation over a short period of time, whereas astronauts on a trip to Mars would be exposed to a low-dose of cosmic rays constantly during the mission.

“On a Mars mission, the dose would be accumulated over the full period of roughly 1,000 days at a very low rate,” Southwest Research Institute scientist Cary Zeitlin told Mashable. “In the lab, a comparable dose can be given, but it has to be done in a short span of time, perhaps a few hours or less. There's simply no other way to do the studies.”

“Does that difference invalidate these results? Not at all,” Zeitlin added. “They've convincingly demonstrated that a low dose of high-energy heavy ions causes physical changes in the brain that are linked to behavioral changes. That point alone justifies further investigation.”

Even the International Space Station isn’t an ideal place to perform cosmic ray exposure experiments. The ISS is somewhat protected from that kind of radiation because of its proximity to Earth.

Artist's conception of a NASA astronaut on Mars. Image: Pat Rawlings/NASA

Mice vs. humans

It’s also difficult to use mice as an analogue for human space travelers when it comes to radiation experiments.

“The main question than is how different are humans?” Francis Cucinotta, a co-author of the new study told Mashable via email. “The types and extent of damage in mice and humans will be the same but we don't know if humans have better CNS [Central Nervous System] repair or redundancy etc. The dose, dose rate and other experimental conditions were excellent in this study but the extrapolation from mice to humans is a major question still to be addressed.”

Some studies also point to the idea that rodents are less susceptible to the ill effects of radiation than people could be, according to Robert Hienz, a behavioral biologist at Johns Hopkins University in Baltimore.

“It's also possible that human exposures might result in greater cognitive deficits than those seen in rodent studies,” he added.

The human body is also able to repair itself when exposed to some radiation; however, research on how people behave when exposed to cosmic radiation for extended periods of time is still thin.

It’s also possible that very low doses of radiation over long periods of time could produce “more severe effects” than high, fast doses because it’s possible that those low, slow doses don’t trigger the body’s repair mechanisms, Hienz added.

“At higher doses, these mechanisms are triggered, so the damage is minimized,” Hienz told Mashable in an email conversation. “All of this is rather speculative, however, since so few studies exist in this area.”

How to solve the problem

Scientists are also looking for ways to mitigate the risks posed by long-term exposure to cosmic rays. Some researchers are working to develop more robust spacecraft systems or even medical methods for reducing the harmful effects of radiation on the human body during spaceflight.

In other words, it might be possible for Mars-bound astronauts to take medication to counteract the radiation.

“We are working on pharmacologic strategies involving compounds that scavenge free radicals and protect neurotransmission,” Limoli said. “But these remain to be optimized and are under development.”