Mars is such a cool planet! Heck.... All of the planets are pretty awesome if you think about it. I find it odd that all of our planets are so close together, but so unalike. The only thing they have in common with regard to characteristics, is that some of them are small rocky planets, and others are huge ‘gas planets’. I’ve always wondered what the inner parts of the gas planets look like. I understand that under the clouds of gas, they have liquid gases and metals, with a small core.
I believe the theory is that much of Jupiter’s core is a form of metallic hydrogen.
The most intriguing suggestion I heard about gas giants is that the core may be carbon, under intense pressure. The theory is that the core of Jupiter could be a diamond the size of Earth.