It was not known that Jupiter had a ring, or for that matter, that any planet other than Saturn had a ring, until the Voyager Spacecraft tour. It was suspected that other planets had rings, and in March 1979, Voyager I flew past Juipiter and confirmed that Jupiter did indeed have a thin delicate ring.
Not only is Jupiter's ring about 100 times less obvious as Saturn's ring system, it is also composed of dark, reddish material. This meant that the particles that made up the ring were not ices, such as Saturn's were, but must be rocky bits instead. Voyager 2 images showed that the ring particles were also very small, most about 10 micrometers or less in diameter.
There is a slight cloud of particles that extend above and below the ring itself, on the side toward Jupiter, the cloud extends down to the cloud tops of the planet itself. These dust particles may be acquiring an electrostatic field and then being pulled out of the ring by Jupiter's magnetic field.
The ring lies inside Jupiter's Roche limit, that area near a planet where a moon would be torn apart by the planet's gravitational forces. This may indicate that the ring is composed of material from a moon that never formed. What is curious is that the ring material is cannot be old. Material is constantly being removed from the ring, either pulled down to Jupiter, or blown away from forces in the magnetosphere. So there must also be a supply of particles for the ring.
A likely source of "ring stuff' would be from pieces of other moons that have been chipped away by meteoritic impacts. There is a small 36 km moon called Adrastea which orbits Jupiter just at the edge of the ring. There is even a moon called Metis which orbits inside the ring itself. These moons also serve a purpose in keeping ring particles inside the ring.
Copyright © 1997 Kathy A. Miles and Charles F. Peters II