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This is a drawing which illustrates the composition of Neptune's atmosphere relative to possibilities for other planets.
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An Overview of Neptune's Atmospheric Composition

The atmosphere of Neptune is very similar to that of Uranus, and unlike that of Saturn and Jupiter. On Jupiter and Saturn, the atmosphere is mostly composed of the simple molecules hydrogen and helium. The atmosphere of Neptune contains a greater percentage of the more complex molecules such as methane gas, ethane gas, acetylene, and diacetylene. These constituents collectively are known as "hydrocarbons".

Hydrocarbons form hazes of smog high in the upper atmosphere. There are clouds of methane ice low in the troposphere.

One of the reasons these molecules are the primary constituents of the atmosphere of Neptune is that Neptune evolved from the more complex hydrocarbons, and ices, rather than solely from hydrogen and helium.


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Neptune's Smog Hazes

This image of Neptune uses false colors to bring out the hazes of smog, which can be seen in red along the limb of Neptune, at the edge of the picture. These hazes of smog are found at very high altitudes,...more

An Overview of Neptune's Atmospheric Evolution

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The Environment of Neptune

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Neptune Clouds, overview

Like Jupiter and all the giant planets, Neptune's appearance shows a striped pattern of clouds. Other cloud shapes seen over time include a small dark spot, the "scooter" and the Great Dark Spot. The Great...more

An Overview of Neptune's Atmosphere

Neptune's atmosphere shows a striped pattern of clouds. This cloud pattern is very similar to that of Jupiter and Saturn. Neptune even has a Great Dark Spot similar to Jupiter's Great Red Spot. The structure...more

Neptune's Present Great Dark Spot

This image shows the new Great Dark Spot of Neptune, which was discovered using the Hubble Space Telescope. The image shown here, shows a "hole" in the clouds of Neptune in pink, in the northern hemisphere,...more

Neptune's Cirrus Clouds

This image shows some cirrus clouds, extending for many kilometers across the disc of Neptune. These clouds are somewhat high up, for they can be seen to cast shadows on the lower clouddeck, which is 35...more

How the Solar System may have formed out of the Primordial Nebula

The solar system contracted, or shrank together, out of a spinning cloud of hydrogen and helium gas. This spinning cloud had a certain amount of momentum, which caused it to flatten, somewhat the way a...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA