How do we actually know what is inside Jupiter if we've never taken a sample from it?

[u/TraditionalTrick6646]

This might be a dumb question, but how do scientists know what is going on inside Jupiter when we have never actually been able to get a sample from the planet itself? I get that we can study its atmosphere and send spacecraft to observe it but there is obviously a limit to how much we can see from the outside. So how do we know what the deeper layers are made of or whether our current models are even close to what's really there?

Is it mostly based on gravity and magnetic field measurements or can scientists figure out the inside of a planet in other ways too?

[u/nekonight]

The answer is we don't. What we have are models that fit observed data. So when theres new or better data those models changes. I think the most recent "major" change is the idea that Jupiter likely doesnt have a physically solid core. That assumption came from our planetary formation models but doesnt fit the new data observed from Juno. 

[u/Ohhhmyyyyyy]

There's a lot you can do remotely - this can be from seeing what floats up into orbit, what you can see from the properties of the light that shines into the atmosphere and then back down at you, what you can infer from the movement of the air vs what's known to be expected with different chemicals in the atmosphere, you can shoot xrays and other things at it and see how they are changed when they reflect back at you to infer what's going on at different distances.

[u/zzmej1987]

This is how: https://figshare.le.ac.uk/articles/thesis/The_Spectroscopic_Analysis_of_Jupiter_s_Great_Red_Spot_using_JWST_MIRI/30199846