They found that Callisto’s ionosphere alone cannot explain all existing observations, but that a subsurface ocean in combination with the ionosphere can. Further exploring which scenarios best fit the data, the researchers predicted that the ocean is likely at least tens of kilometers thick, as measured from the top of the liquid ocean to its seafloor, and encased beneath a solid ice shell that itself could range from tens to hundreds of kilometers thick.

Life on Callisto would have a worldview not unlike that of the Krikkiters.