9. Jupiter: a giant primitive planet
Jupiterís mere wisp of a ring
In 1979 Ė after much debate about the likelihood of finding a ring around Jupiter Ė a search was carried out with a camera on Voyager 1, and a narrow faint belt of material was found encircling the planet in its equatorial plane near the same distance that the energetic particles had disappeared. The ring was not previously observed from Earth because it was too faint and close to the bright planet. Since its discovery, Jupiterís main ring has been detected by Earth-based telescopes sensing infrared radiation, and fully confirmed by the inquisitive eyes of the Galileo spacecraft.
The outer edge of the main ring lies just inside the orbit of the tiny moon Adastea, just 15 thousand meters in size and too small to be seen from Earth. It was discovered by the Voyager spacecraft, as was another tiny moon, named Metis, which is embedded near the bright midpoint of the main ring. The dust generated by meteorite impact on Adastea and Metis can easily escape the small gravity of these moons, accounting for the dense accumulation of particles in the main ring. Some of the microscopic particles are small enough for electromagnetic forces to overpower the effects of Jupiterís gravity, pumping them into the inner halo that is seen above and below the main ring.
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Copyright 2010, Professor Kenneth R. Lang, Tufts University