Thousands of people have volunteered for a potential mission to Mars, but if any of them end up making the trip, they might lose a few brain cells along the way.
New research finds that exposure to cosmic rays during the long journey, expected to take about six to eight months, can damage the brain and lead to dementia-like impairment.
"This is not positive news for astronauts deployed on a two- to three-year round trip to Mars," Charles Limoli, professor of radiation oncology at the UC Irvine School of Medicine, said in a news release. "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."
Limoli said that while certain parts of the spacecraft could be shielded, the brain-dulling particles would still get on board.
"There is really no escaping them," he said.
Astronauts in the International Space Station don't face the same risks as they are protected by the Earth's magnetosphere. However, once outside that protective zone, exposure to cosmic rays -- many of which are remnants of supernova explosions -- becomes a problem.
To mimic that exposure, Limoli and a team of researchers exposed mice to the accelerated charged particles found in cosmic rays. Six weeks after exposure, the mice were found to have inflammation in the brain, which blocked signals among neurons, according to the study published on May 1 in the journal Science Advances.
These alterations in the brain led to changes in how the mice behaved. On tests of memory and learning, mice exposed to cosmic rays were more easily confused and lost their tendency to explore new situations.
“These sorts of cognitive changes could manifest during the mission and could be a real problem,” Cary Zeitlin of the Southwest Research Institute in San Antonio, who was not involved in the study, told the Wall Street Journal.
Zeitlin's research focuses on radiation detected by the Mars Science Laboratory during its 2011-2012 journey to the red planet, and found that it was exposed to the equivalent of a full-body CT scan every five or six days, the paper reported.
While the researchers behind the new study say the length of a trip to Mars would be enough to expose humans to brain-damaging levels of cosmic rays, others aren't convinced.
“The dose rates they are using are approximately a million times greater than what astronauts would experience on a trip to Mars,” Robert Zubrin of the Mars Society told The Space Reporter. Zubrin told NBC News the bigger problem is long-term weightlessness.
"If NASA is concerned about the health of astronauts, the first thing is to address artificial gravity," Zubrin was quoted as saying.
Although NASA did not comment directly on the new study, spokesperson Stephanie Schierholz did release the following statement: “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."
This doesn't mean a manned trip to Mars is out of the question. But it does mean that there's more to the journey than just designing a spacecraft to get people there and back again.
The UC Irvine researchers believe there may one day be a medication to help protect the brain from the type of damage seen in their study.
"But these remain to be optimized and are under development," Limoli said.