Place in atmosphere changes moon's color

"Why is the moon sometimes yellow-orange and not all the time?" asked Sierra Friebolin, 10, a fifth-grader at Adler Park School in Libertyville.

Have you heard of ROY G BIV? That's an acronym for the colors in the light spectrum -- red, orange, yellow, green, blue, indigo and violet.

Colors we see come from light, and light comes from the sun. Color is the visible part of the electromagnetic spectrum.

"The Earth's atmosphere absorbs and scatters different colors of light in different amounts," said Geza Gyuk, director of astronomy at the Adler Planetarium in Chicago. "The more of our atmosphere the moon has to travel through, the more orange or red it becomes. This is the same reason the sun is red at sunset. At 'moonset' or 'moonrise,' the moon is yellow, gold, orange or sometimes even red."

Gyuk said the moon does not produce light. "It's entirely reflected from the sun. The silvery color of the moon most of the time is a reflection of the white color of the sun."

Gyuk said the moon's color can be dramatic during a lunar eclipse. "When the moon enters the Earth's shadow, it still gets some light from the sun." The alignment of sun, Earth and moon gives the appearance of the sun setting behind the Earth. The light from this "sunset" makes the moon appear dark or blood red.

When you look at the moon you can see dark splotches that might remind you of the features on a face.

"Different parts of the moon are differently colored. The large blotches called "maria" are huge flood plains of lava that were produced when an asteroid impact on the moon punched through the crust and the molten magma inside filled the resulting impact crater." Gyuk explained that lighter-colored areas are highlands and are the moon's original crust.