<p>You could just have <a href="https://www.google.co.uk/search?hl=en&amp;q=colour%20of%20gas%20giants&amp;meta=&amp;rlz=1I7ADBF_en-GB&amp;gws_rd=ssl" rel="nofollow noreferrer">Googled this question</a>.</p>
<p>Post #5 from the <a href="https://forum.cosmoquest.org/forum/science-and-space/space-astronomy-questions-and-answers/87928-?p=2386747#post2386747" rel="nofollow noreferrer">first hit</a>:</p>
<blockquote>
<p>First off, by &quot;wondering what colors different gas giants can be&quot;, you
are presumably asking about their light spectra through the visible
range of wavelengths (380-720 nm), right?**</p>
<p>Light interacts primarily with electrons. It is scattered or absorbed
in the presence of electrons, which come in a variety of &quot;phases&quot;.
Here are the most relevant:</p>
<ol>
<li>free within an ionized gas (can absorb in the presence of the
electric field of an ion)</li>
</ol>
</blockquote>
<blockquote>
<ol start="2">
<li>attached to atoms and ions</li>
</ol>
</blockquote>
<blockquote>
<ol start="3">
<li>attached to molecules</li>
</ol>
</blockquote>
<blockquote>
<ol start="4">
<li>attached to molecules that have condensed into solid state aerosols and grains, or liquid droplets.</li>
</ol>
<p><strong>The most important thing to take away from this is that every type of
material, in terms of composition and &quot;phase&quot;, absorbs and scatters
light uniquely.</strong></p>
<p>The prevalence and importance of each of the above four &quot;phases&quot;
depend on (a) the elemental composition of the giant planet's
atmosphere (defined as that layer responsible for light
reflected/emitted by planet), and (b) its equation of state (how
pressure changes as a function of density and temperature). The first
of these provides the raw materials, and the second arranges them in
&quot;phase&quot;. Very roughly speaking, one may assign decreasing temperatures
(T) to the above 4 &quot;phases&quot; moving down the list 1--&gt;4. Pressure (P)
also plays a role, and in general one may place the above phases on a
P-T diagram. Physics and Chemistry are at work to determine what kind
of &quot;stuff&quot; is present as a function of depth through the giant planet
atmosphere. One rule of thumb is that chemistry is much more effective
at higher temperatures (to a point) and/or in the presence of
moderately energetic light.</p>
<p>Next, before proceeding, go back and read the <strong>bold statement</strong>, above.</p>
<p>To finish off this overly long post: Two giant planets of equal bulk
compositions will almost certainly appear differently if their P vs. T
profiles differ, or if their atmospheric compositions differ (e.g.,
due to convective mixing from the interior, mixing due to wind
currents, heterogeneous settling of heavier matter towards the center
over time). Two giant planets of equal bulk compositions, but
differing ages will appear differently, since a planet's interior
cools over time, affecting P-T relation within the planet as well as
its thermally emitted spectrum. The intensity and spectral shape of
the light incident from the parent star will affect the P-T diagram,
the chemistry and phase of the matter, the thermally emitted spectrum,
as well as the distribution of photons available for scattering.</p>
</blockquote>
<p>From the <a href="http://coolcosmos.ipac.caltech.edu/ask/203-Why-do-the-planets-have-different-colors-" rel="nofollow noreferrer">second hit</a>:</p>
<blockquote>
<p>Jupiter is a giant gas planet with an outer atmosphere that is mostly
hydrogen and helium with small amounts of water droplets, ice
crystals, ammonia crystals, and other elements. Clouds of these
elements create shades of white, orange, brown and red. Saturn is also
a giant gas planet with an outer atmosphere that is mostly hydrogen
and helium. Its atmosphere has traces of ammonia, phosphine, water
vapor, and hydrocarbons giving it a yellowish-brown color. Uranus is a
gas planet which has a lot of methane gas mixed in with its mainly
hydrogen and helium atmosphere. This methane gas gives Uranus a
greenish blue color Neptune also has some methane gas in its mainly
hydrogen and helium atmosphere, giving it a bluish color</p>
</blockquote>

CC BY-SA 3.0
2015-02-05T13:24:16.330Z
Your google search results almost certainly differ from mine, or from Joshua (the person who asked the question). Don't assume your first hit is my first hit, or Joshua's. See [Reasons your Google search results are different than mine](http://themetaq.com/articles/reasons-your-google-search-results-are-different-than-mine) for more info.
David Hammen
CC BY-SA 3.0
2015-02-06T18:28:34.303Z
So what? Did you or the OP do a Google search? What were your hits, where they all about the colour of hot air balloons? Are you telling me that your Google search turned up noting about the colours of gas giants? Your hits may well differ, your first hit may be irrelevant, what you do is look at the hits until you find one which is relevant, I doubt you will have had to look far. The only significant difference between mine and others' searches might well be the fierceness of ad blocking. Effective use of Google is a very low grade type of research and everyone should learn how to do it.
Conrad Turner
CC BY-SA 4.0
2015-02-05T06:04:09.820Z
2022-02-02T18:08:35.320Z
2022-02-02T18:08:35.320Z
Conrad Turner
<p>The simple answer is that the composition in terms of elements doesn't matter for the colour, since that is determined by the molecular composition as well as state (pressure and temperature) of the visual layers (which contain a small but significant fraction of other elements than H and He). Given the differences in the giant planets temperature and pressure, this molecular composition is most likely different.</p>

CC BY-SA 3.0
2015-02-05T22:31:19.787Z
2015-02-05T22:31:19.787Z
Walter
<p>As I understand it, Jupiter, Saturn, Uranus, and Neptune are all made primarily from varying proportions of hydrogen and helium.  Despite this, Jupiter is very red, Saturn is yellow, and Uranus and Neptune are blue.  Why the difference in colors for planets with similar chemical makeups?  Or do they not have similar chemical makeups?</p>

<p>If such an explanation is available, I would like specific descriptions of why each planet is colored the way it is.</p>

<solar-system><jupiter><gas-giants><saturn><uranus>
Why are gas giants colored the way they are?
NeutronStar
# Why are gas giants colored the way they are?

(Asked by: username_0 on 2015-02-05)

As I understand it, Jupiter, Saturn, Uranus, and Neptune are all made primarily from varying proportions of hydrogen and helium. Despite this, Jupiter is very red, Saturn is yellow, and Uranus and Neptune are blue. Why the difference in colors for planets with similar chemical makeups? Or do they not have similar chemical makeups?

If such an explanation is available, I would like specific descriptions of why each planet is colored the way it is.

**Tags:** solar-system, jupiter, gas-giants, saturn, uranus

---

## 2 answers

### Answer by username_1 on 2015-02-05. Score: 1 | Accepted answer

You could just have [Googled this question](https://www.google.co.uk/search?hl=en&q=colour%20of%20gas%20giants&meta=&rlz=1I7ADBF_en-GB&gws_rd=ssl).

Post #5 from the [first hit](https://forum.cosmoquest.org/forum/science-and-space/space-astronomy-questions-and-answers/87928-?p=2386747#post2386747):

> First off, by "wondering what colors different gas giants can be", you
> are presumably asking about their light spectra through the visible
> range of wavelengths (380-720 nm), right?\*\*
>
> Light interacts primarily with electrons. It is scattered or absorbed
> in the presence of electrons, which come in a variety of "phases".
> Here are the most relevant:
>
> 1. free within an ionized gas (can absorb in the presence of the
>    electric field of an ion)

> 2. attached to atoms and ions

> 3. attached to molecules

> 4. attached to molecules that have condensed into solid state aerosols and grains, or liquid droplets.
>
> **The most important thing to take away from this is that every type of
> material, in terms of composition and "phase", absorbs and scatters
> light uniquely.**
>
> The prevalence and importance of each of the above four "phases"
> depend on (a) the elemental composition of the giant planet's
> atmosphere (defined as that layer responsible for light
> reflected/emitted by planet), and (b) its equation of state (how
> pressure changes as a function of density and temperature). The first
> of these provides the raw materials, and the second arranges them in
> "phase". Very roughly speaking, one may assign decreasing temperatures
> (T) to the above 4 "phases" moving down the list 1-->4. Pressure (P)
> also plays a role, and in general one may place the above phases on a
> P-T diagram. Physics and Chemistry are at work to determine what kind
> of "stuff" is present as a function of depth through the giant planet
> atmosphere. One rule of thumb is that chemistry is much more effective
> at higher temperatures (to a point) and/or in the presence of
> moderately energetic light.
>
> Next, before proceeding, go back and read the **bold statement**, above.
>
> To finish off this overly long post: Two giant planets of equal bulk
> compositions will almost certainly appear differently if their P vs. T
> profiles differ, or if their atmospheric compositions differ (e.g.,
> due to convective mixing from the interior, mixing due to wind
> currents, heterogeneous settling of heavier matter towards the center
> over time). Two giant planets of equal bulk compositions, but
> differing ages will appear differently, since a planet's interior
> cools over time, affecting P-T relation within the planet as well as
> its thermally emitted spectrum. The intensity and spectral shape of
> the light incident from the parent star will affect the P-T diagram,
> the chemistry and phase of the matter, the thermally emitted spectrum,
> as well as the distribution of photons available for scattering.

From the [second hit](http://coolcosmos.ipac.caltech.edu/ask/203-Why-do-the-planets-have-different-colors-):

> Jupiter is a giant gas planet with an outer atmosphere that is mostly
> hydrogen and helium with small amounts of water droplets, ice
> crystals, ammonia crystals, and other elements. Clouds of these
> elements create shades of white, orange, brown and red. Saturn is also
> a giant gas planet with an outer atmosphere that is mostly hydrogen
> and helium. Its atmosphere has traces of ammonia, phosphine, water
> vapor, and hydrocarbons giving it a yellowish-brown color. Uranus is a
> gas planet which has a lot of methane gas mixed in with its mainly
> hydrogen and helium atmosphere. This methane gas gives Uranus a
> greenish blue color Neptune also has some methane gas in its mainly
> hydrogen and helium atmosphere, giving it a bluish color

> **Comments:**
> **username_2**: Your google search results almost certainly differ from mine, or from Joshua (the person who asked the question). Don't assume your first hit is my first hit, or Joshua's. See [Reasons your Google search results are different than mine](http://themetaq.com/articles/reasons-your-google-search-results-are-different-than-mine) for more info.  
> **username_1**: So what? Did you or the OP do a Google search? What were your hits, where they all about the colour of hot air balloons? Are you telling me that your Google search turned up noting about the colours of gas giants? Your hits may well differ, your first hit may be irrelevant, what you do is look at the hits until you find one which is relevant, I doubt you will have had to look far. The only significant difference between mine and others' searches might well be the fierceness of ad blocking. Effective use of Google is a very low grade type of research and everyone should learn how to do it.  

---

### Answer by username_3 on 2015-02-05. Score: 3

The simple answer is that the composition in terms of elements doesn't matter for the colour, since that is determined by the molecular composition as well as state (pressure and temperature) of the visual layers (which contain a small but significant fraction of other elements than H and He). Given the differences in the giant planets temperature and pressure, this molecular composition is most likely different.


---

