Why is Neptune blue?
Show answer & explanation
Answer: Methane absorbs red light
Distance from sun — Wrong. Distance doesn't determine color. Neptune is blue because atmospheric methane absorbs red light, reflecting blue.
Frozen nitrogen on surface — Wrong. Neptune is a gas/ice giant with no solid surface—frozen nitrogen on a 'surface' doesn't exist. The blue color comes from atmospheric methane absorbing red light.
Methane absorbs red light ✓ — Correct! Neptune's atmosphere contains methane (CH₄). Methane molecules absorb red and infrared wavelengths, reflecting blue and green. Result: striking blue appearance. Uranus also has methane but appears lighter blue-green (less atmospheric activity). Neptune has deeper blue, possibly from unknown chromophore. Ice giants (Neptune, Uranus) differ from gas giants (Jupiter, Saturn)—more ices, less hydrogen/helium!
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