the long term effects of space travel could spell trouble for astronauts
attempting to fly to Mars.
of Mars at the boundary between darkness and daylight, with an area including
Gale Crater beginning to catch morning light, in this handout image provided by
Many things would be difficult about conducting a manned mission to Mars,
from designing a spacecraft that could make the 34-million-mile journey, to
stocking and fueling it, to keeping its astronauts from getting flabby and
On Friday, researchers hut light on another potential obstacle: reckoning
out a way to protect travelers’ brains from the damaging effects of cosmic rays
in outer space.
When University of California, Irvine neuroscientist Charles Limoli and
colleagues exposed mice to radiation similar to that astronauts would encounter
far beyond Earth, the animals experienced changes in their brains that impaired
their performance on tests of learning and memory, the team reported in an
article — “What happens to your brain on the way to Mars” — in the journal
The researchers’ results suggested that astronauts could suffer cognitive
impairment during an extended journey through space.
“Over the course of a two- to three-year mission, the damage would
accumulate,” Limoli said. “To mitigate it, we need to understand it.”
Six weeks later, back in California, they tested the mice’s learning and
memory by placing them in pens with toys, letting them get used to their
surroundings, and then making changes such as introducing a new toy. Mice that
had been exposed to the radiation were less aware of or curious about the
changes in their environment than controls that had not been irradiated — a
sign that they had cognitive deficits.
To test the effects of space radiation on the brain, the researchers took
mice to the NASA Space Radiation Laboratory at the Brookhaven National
Laboratory in New York, which attempts to simulate radiation conditions in
space. They exposed the animals to oxygen and titanium ions, atoms with their
electrons stripped away that are similar to the charged particles in cosmic
“A smart animal will recognize the
change,” Limoli said.
When the researchers later studied the animals’ brain tissue, they found
that mice that performed poorly on the tests also had less dense branching in
their brain cells, due to damage from the radiation. The structural changes
would impede the brain’s ability to transmit signals and process information.
Limoli got involved in the NASA-backed research as an outgrowth of his work
on the effects of radiation on brain cancer patients. Radiation therapy
forestalls brain cancer progression, he said — but it can take a tremendous
toll on the central nervous system, causing depression, anxiety and mood
disorders, and deficits in learning and executive function. Pediatric patients
can lose 20 to 30 I.Q. points after receiving radiation treatments to the
“Doctors have gotten really good at curing cancer, but maintaining a good
quality of life has been a problem,” Limoli said. “This is an unmet medical
Astronauts flying to Mars and getting hit by cosmic rays, which are the
remnants of supernova explosions, wouldn’t get anything close to the high doses
of radiation that cancer patients receive, but they “might be prone to
mistakes,” Limoli thought.
To counteract that threat during planning for a possible mission, scientists
might come up with more advanced shielding options — perhaps embedded in
helmets — or drug treatments that might ameliorate radiation’s impacts on the
brain, similar to the ones Limoli is exploring for cancer patients.