Found lower in the comments section, credit to u/phatsakis:
Its up for debate what Jupiter's core really consists of, here's the Juno mission's page on it:
WHAT’S IN JUPITER’S CORE?
According to most theories, Jupiter has a dense core of heavy elements that formed during the early solar system. The solid core of ice, rock, and metal grew from a nearby collection of debris, icy material, and other small objects such as the many comets and asteroids that were zipping around four billion years ago. These bits of matter clumped together due to their mutual gravity, becoming larger chunks called planetesimals, which, in turn, collided and stuck together to form Jupiter’s core.
Soon, the core grew big enough so that it had enough gravity to attract even hydrogen and helium, the lightest elements that exist. More and more gas accumulated until it became what we now know as Jupiter. Although most scientists agree on this general story, many details remain unknown. For example, we’re still not sure where all the icy matter comes from.
Another theory, however, suggests that there’s no core at all. Instead, Jupiter formed from the large cloud of gas and dust that surrounded the Sun soon after its birth. As this cloud cooled and condensed, gas and dust particles lumped together so that some regions were denser than others. One of these dense splotches was able to gravitationally pull more and more gas and dust together, swelling into a full-fledged planet.
By measuring Jupiter’s gravitational and magnetic fields, Juno will be able to determine whether a core exists. If it does, exactly what the fields look like will depend on how big it is. Different theories make different predictions about the core, and knowing the size will help determine which theory – if any – is more likely to be correct.
If Juno finds no evidence of a core, then that could strengthen the condensed-cloud theory. Another possibility is that Jupiter once had a core, but it has since eroded away. It could also be that whatever Juno finds won’t fit any theory, and scientists will have to come up with completely new ideas.
Also found in another comment section, by /u/astromike23
For the interior of Jupiter, let's imagine taking a descent from cloud-tops down to the core based on our best guesses of what lies below.
You start falling through the high, white ammonia clouds starting at 0.5 atmospheres, where the Sun is still visible. It's very cold here, -150 C (-240 F). Your rate of descent is roughly 2.5x that of Earth, since gravity is much stronger on Jupiter.
You emerge out the bottom of the cloud deck somewhere near 1 atmosphere. It's still somewhat bright, with sunlight filtering through the ammonia clouds much like an overcast day on Earth. Below, you see the second cloud-deck made of roiling brown ammonium hydrosulphide, starting about 2 atmospheres.
As you fall through the bottom of this second cloud deck, it's now quite dark, but warming up as the pressure increases. Beneath you are white water clouds forming towering thunderstorms, with the darkness punctuated by bright flashes of lightning starting somewhere around 5 atmospheres. As you pass through this third and final cloud-deck it's now finally warmed up to room temperature, if only the pressure weren't starting to crush you.
Emerging out the bottom, the pressure is now intense, and it's starting to get quite warm, and there's nothing but the dark abyss of ever-denser hydrogen gas beneath you. You fall through this abyss for a very, very long time.
You eventually start to notice that the atmosphere has become thick enough that you can swim through it. It's not quite liquid, not quite gas, but a "supercritical fluid" that shares properties of each. Your body would naturally stop falling and settle out somewhere at this level, where your density and the atmosphere's density are equal. However, you've brought your "heavy boots" and continue your descent.
After a very, very long time of falling through ever greater pressure and heat, there's no longer complete darkness. The atmosphere is now warm enough that it begins to glow - red-hot at first, then yellow-hot, and finally white-hot.
You're now 30% of the way down, and have just hit the metallic region at 2 million atmospheres of pressure. Still glowing white-hot, hydrogen has become so dense as to become a liquid metal. It roils and convects, generating strong magnetic fields in the process.
Most materials passing through this deep, deep ocean of liquid metallic hydrogen would instantly dissolve, but thankfully you've brought your unobtainium spacesuit...which is good, because it's now 10,000 C (18,000 F). Falling ever deeper through this hot glowing sea of liquid metal, you reflect that a mai tai would really hit the spot right about now.
After a very, very, very long time falling through this liquid metal ocean, you're now 80% of the way down...when suddenly your boots hit a solid "surface", insomuch as you can call it a surface. Beneath you is a core weighing in at 25 Earth-masses, made of rock and exotic ices that can only exist under the crushing pressure of 25 million atmospheres.
You check your cell phone to tell you friends about your voyage...but sadly, it melted in the metallic ocean - and besides, they only have 3G down here.
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u/jdreckie7 Dec 29 '20
What would happen if you were to “land” on Jupiter ? Just go straight through ?