Humans hoping to launch themselves to another planet or even into the Sun are sadly out of luck -- for now. But in a few billion years, when the Sun becomes a red giant and destroys our terrestrial oceans, future folk will hypothetically be able to make their homes elsewhere. Saturn and Jupiter's icy moons -- Enceladus and Europa, respectively -- have topped the list for future Earthling getaways. But new research suggests that these worlds might not be so habitable, even after their icy surfaces melt.