Because of better spatial resolution, different phase coverage, and superior signal-to-noise, Galileo's thirteen clear images of Jupiter's ring system taken during a single pass through the planet's shadow improve substantially upon Voyager data. In addition two Adrastea images fortuitously included the rings at phase angles around 83(deg) . By assuming a circular and equatorial main ring, and using the position of a star found in one ansa image, we fix the main ring's outer radius at 128940+/-50 km, slightly less than Voyager's value of 129130+/-100 km, and very close to Adrastea's orbit (128980 km). The ring's halo rises gradually starting near the 3:2 vertical Lorentz resonance at 122733 km. The gossamer ring, discovered in a single Voyager image, is clearly visible out to the frame's edge at 2.3 RJ. The main ring exhibits a marked drop in brightness at 127849+/-50 km, lying almost atop Metis's orbit at 127978 km. The ansa images also show apparent azimuthal structure: longitudinally alternating bright and dim patches. As previously noted in Voyager images, the brightnesses of the near and far arms differ by 10% or more. In contrast to Voyager, Galileo images show the near arm to be brighter. Galileo's shallow viewing angle (0.5(deg) above the ring plane) through the diaphanous ring may play a role in brightness variations. Results will also be presented describing the morphologies of the halo and gossamer ring, as well as phase functions for the ring's components.
AAS/Division for Planetary Sciences Meeting Abstracts #29
- Pub Date:
- July 1997