How do we know that there is a salty ocean underneath Europa’s icy surface?

Question

Europa is one of Jupiter’s moons and apparently has a “water-ice crust”, “salty ocean of liquid water”, and a “rocky sea floor”. How could we know this much information in great detail from a telescope?

In: 101

Answer 1

I know some icy moons like Enceladus shoot water out of their surface, and we use spectroscopy to find out what’s in the water. I looked it up and there’s a theory that Europa has some too. But it makes sense they’d be harder to spot, Europa has over 10x stronger surface gravity than Enceladus.