Armageddon is probably not going to be tomorrow, and neither is a zombie apocalypse, but fast-forward a few billion years and the sun will eventually morph into a fiery red giant that mercilessly dries up our oceans and turns all Earth’s human inhabitants into dry bones.
That is, unless we figure out somewhere else to take off to several billion years in advance.
If this all sounds like an interplanetary version of The Walking Dead, it kind of is. What we will need to survive as a species if our planet gets burned out is somewhere else with a decent water supply. And when the sun gets that monstrous, there are icy worlds it will inevitably melt. Enter Enceladus and Europa.
Escaping to a formerly subzero planet whose ice ends up melting into water sounded like a doomsday plan until a team of scientists proved otherwise, with research recently published in Nature Geoscience. Using 3D global climate models to simulate the fate of frozen worlds similar to those moons after an F- or G-type star (like the sun) starts its death throes, they found that at such insane levels of heat, our G-type star will have no issues melting all that ice—and vaporizing it. Meaning, an insta-transition from an “icehouse state” to a “greenhouse state” without a habitable phase.
Even with this grim prospect, the human race isn’t doomed. Yet.
“There’s a couple caveats,” said Ramses Ramirez, a research associate in the Carl Sagan Institute at Cornell University, who co-authored this and another study on the future phenomenon. “This really only applies to F and G stars, so stars like [our] Sun or a little brighter than our Sun.”
Humans who would rather not be charbroiled in the future may still be able to rocket away to icy exomoons around cooler K- and M-type stars that have a lower luminosity than our own. When the ice on such moons melts, there is a much higher chance for habitability. Ramirez noted that if a melted Europa and Enceladus had doppelgangers orbiting such stars, they would probably be a safe zone.
Anyone anxious that our species will end up extinct if we can’t find a habitable exomoon shouldn’t give up on Europa and Enceladus just yet. The model is exactly that—a model—and the history of our solar system shows that icehouse states haven’t exactly changed into greenhouse states overnight. Earth has been a fireball at some points and a snowball at others. Mars (as anyone who has any prospects of taking a SpaceX rocket there someday probably knows) was supposedly flowing with liquid water until it dried up and froze. Then there’s that speculation about a possible subsurface ocean on Europa.
There are still too many uncertainties to totally eliminate Europa or Enceladus as prospects for future Earthling escapes, so at least for now, as scientists delve deeper into this research, let’s just fantasize about colonizing Mars.