Jupiter and Saturn contain mostly hydrogen and helium. Uranus and Neptune contain a greater fraction of heavier materials associated with compounds such as water, ammonia and methane. The cutaways are simplified categories, not measurements of exact layer thickness. All four giants have substantial atmospheres.
Space · Discover & try
What makes a planet rocky or giant?
Reading level 4 of 5 · FluentChange
Word help
Terrestrial
A rocky planet such as Earth or Mars.
Gas giant
A giant planet dominated by hydrogen and helium.
Ice giant
A giant with a larger fraction of heavier compounds; not a ball with a frozen outer surface.
Watch · Try · Explain
See how it works
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Original conceptual cutaways; layer fractions and planet sizes are not to scale.
What to look for
- Compare surface with atmosphere.
- Compare the two giant categories.
- Look for a rocky world with thick clouds.
Explain what you noticed
A newly described planet has a solid rocky surface beneath a thick atmosphere. Which conclusion follows?
Keep this idea: A planet’s composition and structure matter more than its colour.
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Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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