We’ve known for some time that space affects your muscles and bones. It forces astronauts to run on a treadmill while in space, proving that no matter how far away you are from Earth, you’ll never escape your Equinox membership. A new study suggests that space travel may be having a more profound and unexpected effect on the bodies of astronauts: it’s rapidly aging them.

No, it’s got nothing to do with time dilation. This isn’t Interstellar.

In a new study published in Cell Stem Cell, led by UC San Diego biochemist Jessica Pham, researchers sent some human hematopoietic stem and progenitor cells (HSPCs) aboard SpaceX missions. They let them hang out on the International Space Station for up to 45 days.

Under the stress of microgravity and cosmic radiation, these cells that produce and m

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