Why is the size of a moon often not the best indicator of its scientific priority?

Smaller moons can provide faster and cheaper data through methods like plume sampling.

In planetary science, there is a distinct paradox where the largest bodies are not always the most urgent targets for exploration. While large moons like Ganymede are fascinating, their sheer size and thick crusts make direct study difficult and expensive, requiring complex drilling or landing missions. Conversely, smaller moons like Enceladus offer high scientific return for less investment. Because these smaller bodies can naturally expose their internal composition through activity like geysers or plumes, they provide a much easier window into their subsurface oceans. This capability allows researchers to gather critical data on potential habitability and chemical makeup much more quickly and cost-effectively than they could with larger, more isolated targets.