Jupiter, Io and Europa

Wallpaper Description:

Voyager 1 took this photo of Jupiter and two of its satellites (Io, left, and Europa) on February 13, 1979. Io is about 350,000 kilometers (220,000 miles) above Jupiter's Great Red Spot; Europa is about 600,000 kilometers (375,000 miles) above Jupiter's clouds. Although both satellites have about the same brightness, Io's color is very different from Europa's. Io's equatorial region show two types of material—dark orange, broken by several bright spots—producing a mottled appearance. The poles are darker and reddish. Preliminary evidence suggests color variations within and between the polar regions. Io's surface composition is unknown, but scientists believe it may be a mixture of salts and sulfur. Europa is less strongly colored, although still relatively dark at short wavelengths. Jupiter is about 20 million kilometers (12.4 million miles) from the spacecraft.

NASA / JPL