It’s long been known that exposure to radiation damages DNA, but a new study has found an additional risk for astronauts: DNA replication is more prone to errors in microgravity.

Scientists tested whether enzymes accurately copy DNA in cells during microgravity — the weightlessness produced during the freefall of a jet on a parabolic flight pattern. When the so-called “vomit comet” descends more than 2 miles in 20 seconds, the near-weightlessness replicates conditions in space. Accurate DNA replication in space is crucial for astronauts and the future of space travel.

“So-called DNA polymerases are essential enzymes that copy and repair DNA. Inevitably, they aren’t perfect: even under optimal conditions, they sometimes make mistakes. Here, we show that DNA polymerases derived from the bacterium E. coli are considerably more prone to errors under microgravity, such as occurs in space,” said Aaron Rosenstein of the University of Toronto, corresponding author of the study published in Frontiers in Cell and Developmental Biology.