NASA says that new evidence shows that Jupiter’s moon Europa was probably once spinning on a titled axis. And they say this explains one of the great mysteries of Europa—why its long, straight cracks have changed over time. Tidal forces cause Europa’s surface to stretch and shrink in accordance with its proximity to Jupiter, resulting in the cracks we see. But scientists have never understood why they crack in different directions. New data from the Galileo spacecraft indicates that the moon may have once had a titled axis, which would have changed the orientation of the pole over time and created the seemingly random cracks.