Amid a lot of talk about crewed missions to the moon and the coming era of much longer crewed missions to Mars and beyond there’s one thing that doesn’t get discussed enough—and that’s gravity. More specifically, the importance of gravity to humans and the need to develop spacecraft with artificial gravity.
That’s underscored today by the publication in the journal Scientific Reports today of a new study of 30 astronauts that reveals long spaceflights take such a toll on the human brain that a three-year break between missions should be considered by space agencies.
The study found physiological changes in the brains of astronauts that were at their most dramatic among those who stayed in space the longest—though changes may plateau after six months.
How spaceflight changes the human brain
The absence of gravity expands cavities in the brain called ventricles, which provides protection, nourishment and waste removal to the brain. The longer you stay in space, the more they expand. For astronauts in space for longer than six months it may take three years for the ventricles to shrink back to normal size, says the report.
“We found that the more time people spent in space, the larger their ventricles became,” said Rachael Seidler, a professor of applied physiology and kinesiology at the University of Florida and an author of the study. “Many astronauts travel to space more than one time, and our study shows it takes about three years between flights for the ventricles to fully recover.”
Ventricular expansion is the most enduring change seen in the brain as a result of spaceflight. The problem, of course, is the absence of gravity. It causes fluid to shift upward, pushing the brain higher within the skull and causing the ventricles to expand.
Space tourism declared safe
Space tourists need not worry since short trips appear to cause little physiological changes to the brain. “The biggest jump comes when you go from two weeks to six months in space,” said Seidler. “There is no measurable change in the ventricles’ volume after only two weeks.”
Some other good news is that there appears to be little further change to the size of ventricles after six months. “We were happy to see that the changes don’t increase exponentially, considering we will eventually have people in space for longer periods,” said Seidler.
In theory that may mean trips to Mars—most of which would take 800 to 1,000 days to complete—would be no more damaging than spending six months in space.
But there’s a problem.
Recovery position
Data came from 30 astronauts:
- Eight traveled to space for two weeks.
- 10 traveled to space for six-months.
- Four traveled to space for just under a year.
In seven astronauts who had less than three years between missions the size of their ventricles appeared not to shrink back to their normal size, suggesting a three-year break is needed.
NASA astronaut Mark Vande Hei returned from 168 days in space on February 28, 2018 only to launch once again on April 9, 2021—just over three years later—on a 355 day mission. There are three other NASA astronauts who have spent more than 300 days in space in recent years.
Although the study’s authors reported that ventricular enlargement tapered off after six months, beyond a year in space there is no data. “We don’t yet know for sure what the long-term consequences of this is on the health and behavioral health of space travelers,” said Seidler, “so allowing the brain time to recover seems like a good idea.”
It makes the once-in-15-years opportunity in 2033 to send a relatively short 570 days mission on a flyby of Mars and Venus seems like a necessary step in sending humans on long space flights.
Wishing you clear skies and wide eyes.
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