Until a few decades ago, no human could have stayed away from the loving embrace of gravity. As the era of space exploration begins, it is still unclear how long it will take to stretch the body without gravity. A new analysis of astronauts from the University of Oregon Health and Science shows that their brains undergo structural changes from exposure to microgravity, and that these changes can persist long after they return to Earth. But there is a limit to how much the brain can change.
There is growing interest in the way human biology deals with space travel. We have been focusing on low-Earth orbits for decades, and even the Apollo-era moon missions were conducted within a few days. With NASA’s long-term presence in lunar orbits and spacecraft magnets like Elon Musk talking about humans exploding on Mars, issues such as aging, brain function and radiation exposure in space have become hot topics.
Working with a team of U.S. doctors, the team performed MRI scans on 15 astronauts. They collected the scans six months before their mission to the International Space Station and then another set of scans six months after their return. The researchers were interested in perivascular space – the space around blood vessels that is believed to help balance cerebrospinal fluid in the brain. These spaces are essential for a process known as the glimphatic system that clears metabolic proteins that otherwise make and cause damage.
For the first time ISS astronauts, the team discovered a larger perivascular space in the brain a few months after returning from space. This same process occurs on Earth as the brain ages, suggesting that the time spent in microgravity may be accelerated. However, experienced astronauts have shown somewhat different results. Their perivascular spaces have not changed since their mission, which suggests two things. First, their brains may have reached some sort of “homeostasis” in increasing perivascular space. Second, spaces are not shrinking to a “normal” shape over time. The team did not notice any cognitive or physical impairment from these changes.
It is still unclear how long-lasting stability in space can alter the brain, but this study provides good evidence that short trips do not cause increasing damage to the glimphatic system. That’s just a potential problem, though. Since people spend more time away from the only home we know, we may find human biology much more or less powerful. If this happens later, Elon Musk’s dream of colonizing Mars within a decade could be shattered.