For nearly two decades, the International Space Station has circled high above us with a crew on board. These astronauts and cosmonauts from a variety of different countries come together to conduct experiments aimed at improving life not just for the humans down below, but for future travelers that might one day make similar journeys into the unforgiving vastness of space. The science tied to that endeavor, in fact, rarely stops when these men and women return to earth after their tenure in the heavens comes to a close. Scientists have long striven to better understand the effect space can have on the human body — and there’s no better way to learn than to study the very humans who have lived in that environment.

One such study, conducted under the purview of Russia’s NASA equivalent, Roscosmos, has spent years collecting data on the brains of active cosmonauts both immediately after their return from rotations aboard the ISS and again seven months later. In order to qualify for the study, each cosmonaut needed to spend 189 days in space (about six months), allowing the human body enough time to acclimate to its environment in space and then allowing seven more months to see how well the body rebounds from that shift.

The results of the study were troubling for anyone that hopes to one day see the human race venturing deeper into space: it seems that some deformation of the brain, caused by exposure to microgravity, may be permanent.

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