Ocean worlds are a group of planetary bodies in our outer solar system known to have liquid water oceans. Rather than existing inside the narrowly defined “Goldilocks Zone,” where water is required to exist on the surface, they contain vast oceans beneath a thick ice crusts. Many of them also have rocky seafloors like we have on Earth, raising the possibility that they could support chemosynthetic life similar to what we find at hydrothermal vents, cold seeps and other forms of seafloor fluid flow on Earth—both known and yet to be discovered.