<p>The reason the hydrogen and helium (that make up most of the mass of planets like Jupiter) remain as gases and don't condense is essentially the same as any other gas. So I could ask "why don't the nitrogen and oxygen in the atmosphere of the Earth condense?"</p>

<p>The reason is that the temperature and pressure in the planet's atmospheres do not favour the formation of a solid. Hydrogen and Helium both have very low boiling points, and even under extreme pressure they tend to remain as a gas.</p>

<p>Further inside the planet the pressure does become sufficent to cause the hydrogen to condense into a liquid, or more properly a supercritical fluid (as at these high pressures the distiction between a gas and a liquid is blurred.  The temperatures are too high for solid hydrogen to form.</p>

<p>There are a couple of things I don't fully understand about your question, which may point to misconceptions. For example most of the mass of Jupiter is in the form of gas, and so most of the gravity comes from the gas, and not from the core (solid or otherwise).</p>

<p>There are layers in the atmosphere of Jupiter. The outer layers are actually rather similar to those in Earth's atmosphere. There is a turbulent troposphere and a stable stratosphere, with a warmer exosphere extending into space. Inside there are layers of supercritical hydrogen and helium and deep inside the pressures cause the hydrogen to behave like liquid metal.</p>

<p>Studying the gravity field (by careful observations of orbiters) is one of the principle ways that we can investigate the internal structure of Jupiter. This suggests that the heavier elements are not concentrated in the core, but mixed in the internal layers, suggesting that the planet has undergone some kind of extreme event in during its formation.</p>

CC BY-SA 4.0
2020-02-16T11:52:27.993Z
2020-02-16T11:52:27.993Z
James K
<p>It has been postulated that Gas Giants have a solid core and an obvious gaseous atmosphere.  Question:  As the gas is a state of matter and gravity draws all matter inward, is the reason the gas is not drawn towards the core and condensed into a solid because the extent of the effect that the gravity has on the gas proportional to the mass of that gas.  Additionally, wouldn't this create a series of unique gaseous layers and wouldn't the depth of those unique layers be contingent on the layers composition.  Also, could the gravitational effect on the known layers be used to determine the composition of the core.  </p>

CC BY-SA 4.0
2020-02-16T13:39:35.523Z
Re *Additionally, wouldn't this create a series of unique gaseous layers and wouldn't the depth of those unique layers be contingent on the layers composition.* This is a common misconception. If this were the case, the Earth's atmosphere would comprise an unbreathable 2 meter thick layer of carbon dioxide at the bottom, above which would lie an equally unbreathable 56 meter thick layer of argon, above which would lie thick layers of pure oxygen and then pure nitrogen. That obviously is not the case.
David Hammen
CC BY-SA 4.0
2020-02-16T17:02:32.017Z
Saturn is *measured* to have a solid core of around 10-20 Earth masses.
ProfRob
<gravity>
Gas Planets composition and gravitational effects
Kevin Whitesides
# Gas Planets composition and gravitational effects

(Asked by: username_0 on 2020-02-16)

It has been postulated that Gas Giants have a solid core and an obvious gaseous atmosphere. Question: As the gas is a state of matter and gravity draws all matter inward, is the reason the gas is not drawn towards the core and condensed into a solid because the extent of the effect that the gravity has on the gas proportional to the mass of that gas. Additionally, wouldn't this create a series of unique gaseous layers and wouldn't the depth of those unique layers be contingent on the layers composition. Also, could the gravitational effect on the known layers be used to determine the composition of the core.

**Tags:** gravity

> **Comments:**
> **username_1**: Re *Additionally, wouldn't this create a series of unique gaseous layers and wouldn't the depth of those unique layers be contingent on the layers composition.* This is a common misconception. If this were the case, the Earth's atmosphere would comprise an unbreathable 2 meter thick layer of carbon dioxide at the bottom, above which would lie an equally unbreathable 56 meter thick layer of argon, above which would lie thick layers of pure oxygen and then pure nitrogen. That obviously is not the case.  
> **username_2**: Saturn is *measured* to have a solid core of around 10-20 Earth masses.  

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## 1 answers

### Answer by username_3 on 2020-02-16. Score: 4

The reason the hydrogen and helium (that make up most of the mass of planets like Jupiter) remain as gases and don't condense is essentially the same as any other gas. So I could ask "why don't the nitrogen and oxygen in the atmosphere of the Earth condense?"

The reason is that the temperature and pressure in the planet's atmospheres do not favour the formation of a solid. Hydrogen and Helium both have very low boiling points, and even under extreme pressure they tend to remain as a gas.

Further inside the planet the pressure does become sufficent to cause the hydrogen to condense into a liquid, or more properly a supercritical fluid (as at these high pressures the distiction between a gas and a liquid is blurred. The temperatures are too high for solid hydrogen to form.

There are a couple of things I don't fully understand about your question, which may point to misconceptions. For example most of the mass of Jupiter is in the form of gas, and so most of the gravity comes from the gas, and not from the core (solid or otherwise).

There are layers in the atmosphere of Jupiter. The outer layers are actually rather similar to those in Earth's atmosphere. There is a turbulent troposphere and a stable stratosphere, with a warmer exosphere extending into space. Inside there are layers of supercritical hydrogen and helium and deep inside the pressures cause the hydrogen to behave like liquid metal.

Studying the gravity field (by careful observations of orbiters) is one of the principle ways that we can investigate the internal structure of Jupiter. This suggests that the heavier elements are not concentrated in the core, but mixed in the internal layers, suggesting that the planet has undergone some kind of extreme event in during its formation.


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