Hey Bill Nye! Why Don't Gas Giants Have Gas Moons?

A very small person asks a very big question: why aren't the moons of gaseous planets also made of gas?

It took a very small person to ask a big question, one that planetary scientists pondered for a long time. There are four gas giants in our solar system – Jupiter, Saturn, Uranus and Neptune – but why are their moons not made of gas? They’re solid, unlike the planets they orbit.

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