What can astronomers tell us about the different colors on the surface of Jupiter's moon Europa?

We can use the colors of Europa’s surface to tell us about the chemical compounds that make up the surface — and subsurface — of the jovian moon. Even before the first spacecraft made a close visit to Europa, astronomers on Earth used telescopes to study the moon and were able to use a technique called spectroscopy to determine that Europa’s surface is composed mostly of water ice.

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