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Glossary Definition: Spectra - Windows to the Universe

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This image shows spectral information collected from the Earth's moon.
Click on image for full size


Minerals of a planet's surface, and molecules of an atmosphere give off light of various colors. Some rocks emit more light in the blue end of the spectrum than the red, and so on. These colors are very hard to see without special cameras. The colors are different for each individual mineral or molecule, and is called that mineral or molecule's spectra. Thus the spectra of a mineral or molecule is like a human fingerprint, and can be used to identify it.

When studying the planets, scientists use special cameras which can collect separate colors of light. Instruments such as these help scientists determine what a planet is made from. Such an instrument is called a spectrometer.

The picture shows what information is gained from spectra. (The colors of the picture have been falsely changed). Pink is very old pulverized ground, oranges and blues are lava flows, light blue are areas which are rich in minerals which have come from meteorites.

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