Haritha’s Reviews > Imagined Life: A Speculative Scientific Journey among the Exoplanets in Search of Intelligent Aliens, Ice Creatures, and Supergravity Animals > Status Update

Okay this is nuts: it seems Pluto has an ocean of water under its surface, but we can't figure out what's keeping it liquid. Pluto is not large enough to have a hot core, and there is no large body nearby to provide tidal forces like the moons of Jupiter and Saturn. Trefil & Summers simply point out this mystery, and then move on. 😳