# Planets with Rock Cores? **URL:** \ **Category:** Factual Questions\ **Created:** [October 25, 2001, 4:13pm UTC](https://boards.straightdope.com/t/planets-with-rock-cores/89573 "2001-10-25T16:13:16Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![don\_willard](https://avatars.discourse-cdn.com/v4/letter/d/a88e57/32.png) [@don\_willard](https://boards.straightdope.com/u/don_willard)\ **Post date:** [October 25, 2001, 4:13pm UTC](https://boards.straightdope.com/t/planets-with-rock-cores/89573/1 "2001-10-25T16:13:16Z")
Do Jupiter, Saturn, Uranus, and Neptune have rock cores inside? Are they all slush of water and then rock farther down? I heard that Uranus has a solid core the size of the earth and the rest is slush and then gas. I just have a hard time knowing the size of these planets when they don’t state it in terms of the solid part, as with earth and the other inner planets. Suppose you towed Jupiter in toward the sun, the frozen part would melt and then they wouldn’t count the atmosphere of gases, they would say oh it is the size of the solid part. Thus I’m getting the idea that it is just by custom that they count the gas and layer of frozen liquid when they give the size of the outer planets because the gas is what is illuminated and makes the planet look bigger from our earth telescopes! Then there is the problem of Pluto… ---
**Author:** ![saepiroth](https://avatars.discourse-cdn.com/v4/letter/s/b5ac83/32.png) [@saepiroth](https://boards.straightdope.com/u/saepiroth)\ **Post date:** [October 25, 2001, 7:00pm UTC](https://boards.straightdope.com/t/planets-with-rock-cores/89573/2 "2001-10-25T19:00:33Z")
uh, jupiter has a solid core, thoug i don’t know if it becomes rock at the depths. simply because of the planet’s size, it has compressed the hydrogen gas that composes it into a pure metallic state. ergo, a good bit of the planet is solid hydrogen metal. however, it really should have some sort of nickel and rock core, if only so it could act as an accumulation point for all the gas. so, it has a solid core, but there’s a chance that the whole thing will boil away if it is drawn to mercury’s orbit. or it might not. IANAAstronomer, though. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [October 25, 2001, 7:30pm UTC](https://boards.straightdope.com/t/planets-with-rock-cores/89573/3 "2001-10-25T19:30:23Z")
Okay, it’s been almost half an hour and I’m still laughing my ass off. Maybe _this_ is what you meant to say, **saepiroth** : > [@](#): > > The gas planets do not have solid surfaces, their gaseous material simply gets denser with depth (the radii and diameters quoted for the planets are for levels corresponding to a pressure of 1 atmosphere). What we see when looking at these planets is the tops of clouds high in their atmospheres (slightly above the 1 atmosphere level). > > Jupiter is about 90% hydrogen and 10% helium (by numbers of atoms, 75/25% by mass) with traces of methane, water, ammonia and “rock”. This is very close to the composition of the primordial Solar Nebula from which the entire solar system was formed. Saturn has a similar composition, but Uranus and Neptune have much less hydrogen and helium. > > Our knowledge of the interior of Jupiter (and the other gas planets) is highly indirect and likely to remain so for some time. (The data from Galileo’s atmospheric probe goes down only about 150 km below the cloud tops.) > > Jupiter probably has a core of rocky material amounting to something like 10 to 15 Earth-masses. > > Above the core lies the main bulk of the planet in the form of liquid metallic hydrogen. This exotic form of the most common of elements is possible only at pressures exceeding 4 million bars, as is the case in the interior of Jupiter (and Saturn). Liquid metallic hydrogen consists of ionized protons and electrons (like the interior of the Sun but at a far lower temperature). At the temperature and pressure of Jupiter’s interior hydrogen is a liquid, not a gas. It is an electrical conductor and the source of Jupiter’s magnetic field. This layer probably also contains some helium and traces of various “ices”. From [http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html](http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html) Hope this helps. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 25, 2001, 8:52pm UTC](https://boards.straightdope.com/t/planets-with-rock-cores/89573/4 "2001-10-25T20:52:01Z")
One of the main reasons that nobody ever talks about the size of a gas giant’s core is that nobody knows. Ask five planetologists, you’ll get at least six different answers. On the other hand, we can say just where the visible top of the clouds is. There’s also the matter that most of the mass is in the gas, not the solid. There’s _something_ out there beyond the asteroids that has a tenth of a percent of the mass of the sun, and it’s not a piece of rock. ---
**Author:** ![saepiroth](https://avatars.discourse-cdn.com/v4/letter/s/b5ac83/32.png) [@saepiroth](https://boards.straightdope.com/u/saepiroth)\ **Post date:** [October 25, 2001, 10:43pm UTC](https://boards.straightdope.com/t/planets-with-rock-cores/89573/5 "2001-10-25T22:43:52Z")
oops. kill me for my insolent and ignorant errors. here’s the sword… ```auto [} ::::::::::;;;;;;;;;;;;;;;;;;;;;;;;;;/ [} ``` ---
**Author:** ![Cargogal](https://avatars.discourse-cdn.com/v4/letter/c/48db29/32.png) [@Cargogal](https://boards.straightdope.com/u/Cargogal)\ **Post date:** [October 25, 2001, 10:48pm UTC](https://boards.straightdope.com/t/planets-with-rock-cores/89573/6 "2001-10-25T22:48:46Z")
I think most planets have more of an easy listening core. [ducks and runs]