The gas giants have always been a mystery to us. Due their dense and swirling clouds, it is impossible to get a good look inside them and determine their true structure. Given their distance from Earth, it is time-consuming and expensive to send spacecraft to them, making survey missions few and far between. And due to their intense radiation and strong gravity, any mission that attempts to study them has to be do so carefully.
What's at the centre of a gas giant?
Juno's View of Jupiter's Turbulent Poles
What is Jupiter Made Of?
Why do the gas giant planets have so much gravity when they do not have solid cores like the terrestrial planets? Or do they have solid cores?
Jupiter's Core vs. Earth's Core
We've been to Jupiter before but haven't looked into its mysterious soul
NASA's Juno orbiter has sent back Jupiter photos “like nothing we have seen or imagined before” - Vox
Does Jupiter have a solid core of anything or is it truly just a large ball of gas? : r/askscience
Jupiter: Anatomy of a Gas Giant