Pretend, for a moment, that you’re one of the first travelers taking a trip to Mars. What would be on your mind? Surely the journey itself will be stressful, and you’ll probably be juggling a number of things in your brain every waking second, not to mention worrying about what life will be like when you finally arrive on the Red Planet.

A new study published in the journal eNeuro suggests that these totally reasonable anxieties may be boosted by radiation exposure during the flight through space, raising concerns over human suitability for deep-space missions.

The study focuses on low-dose radiation exposure experiments in mice, and the researchers argue that their simulation is not only realistic but also rather frightening as NASA takes the first steps towards hashing out crewed missions to Mars.

“As NASA prepares for a mission to Mars, concerns regarding the health risks associated with deep space radiation exposure have emerged,” the researchers explain. “Using a new, low dose rate neutron irradiation facility, we have uncovered that realistic, low dose rate exposures produce serious neurocognitive complications associated with impaired neurotransmission.”

For the experiment, the team exposed lab rodents to months of low-intensity radiation. After six months of exposure, the animals exhibited “striking neurobehavioral and electrophysiological defects,” according to the researchers. A crewed trip from Earth to Mars will likely take anywhere from six to eight months.

Past research has demonstrated that radiation exposure can cause cognitive changes, but there’s been little research into the specific effects of low-dose radiation like the kind that space travelers could be faced with during extended missions to Mars and beyond. This new study suggests that the risk of cognitive issues is significant and that exposure to radiation in space may dramatically increase anxiety.

Protecting travelers from the dangers of space will be NASA’s top priority as it inches closer to sending humans to another planet. Ensuring a spacecraft has the protective capabilities to keep the crew healthy (and happy) will be a major challenge, and radiation exposure will most definitely have to be accounted for.