Hidden oceans beneath an icy surface aren’t a wild idea; in our own Solar System, Saturn’s moon Enceladus and Jupiter’s moons Europa and Ganymede all have worldwide oceans of liquid water sloshing around beneath miles of icy crust. Those icy moons get much of their internal heat from the tidal pull of the gas giants they orbit, but Ojha and his colleagues say heat from radioactive elements decaying in a planet’s interior could also do the trick.
Our own planet proves it’s possible. Beneath Arctic permafrost in parts of Canada, and beneath the ice of Antarctica, lie lakes of chilly — but liquid — water. Heat produced by radioactive elements in Earth’s crust keeps the water warm enough not to freeze.
“There is even some evidence to suggest that this might even be happening currently in the south pole of Mars,” says Ohja.
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