Question

, What's the inner core of the Jovian planets made of?
Question

Answer 1

"Jovian planets" usually means the giant planets in our solar system: Jupiter, Saturn (the gas giants) and Uranus, Neptune (the ice giants). Their inner regions are not like Earth's solid iron core; instead they have dense, high-pressure mixtures of heavier elements. In brief:

- Jupiter and Saturn
- Outer envelope: mostly molecular hydrogen and helium.
- Deep interior: hydrogen is compressed into a metallic, electrically conducting fluid.
- Central region/core: a dense concentration of heavier elements — rock (silicates, metals) and “ices” (water, ammonia, methane) — probably mixed with or surrounded by metallic hydrogen. Models and Juno/Cassini gravity data indicate the core may be compact or partly diluted/extended rather than a sharp solid ball; typical estimates are on the order of a few to a few tens of Earth masses in heavy elements.

- Uranus and Neptune
- Thinner H/He envelopes and much larger amounts of heavier volatiles.
- Interior dominated by a hot, dense “icy” mantle (water, ammonia, methane) in exotic high‑pressure states (ionic or superionic phases), overlying a rocky/metallic central core. The core is likely a mixture of rock and metal rather than pure iron.

All of this is subject to uncertainty because we infer interiors from gravity, magnetic fields, and models; direct sampling is impossible. Under the extreme pressures and temperatures inside these planets, materials behave very differently than at Earth‑surface conditions.