Jupiter's Ring System Resolved: Physical Properties Inferred from the Voyager Images.
Abstract
The 25 Voyager images represent nearly all of the data now in existence on Jupiter's insubstantial ring system. We have developed techniques which allow a surprising amount of information to be extracted from these data. Our analysis involves precise determination of the geometry and smear in each image, and uses pixel averaging methods which permit vast improvement in signal over noise. In addition, contrast enhancement via computer graphics has made it possible to see many subtle features in the frames which had been previously overlooked. The Jovian ring system consists of three components: the bright ring, vertically-extended halo and external "gossamer" ring. The interior disk reported by previous investigators is absent. The bright ring has an abrupt (< 200 km wide) outer boundary centered at orbital radius 129130 100 km, and a broader inner boundary at (TURN)122000 km. It reveals fine structure on scales of a few hundred km, some of which is associated with the embedded satellites Adrastea and Metis. It contains a large population of micron-sized grains, which obey a power-law size distribution n(r) (PROPORTIONAL) r('-p), with p = 2.5 (+OR-) 0.5. Here n(r)dr is the number of particles per unit ring area with radii between r and r + dr. These grains account for an optical depth (tau) = 1-6 x 10('-6) for r < 100 (mu)m. The ring also contains a separate population of larger bodies, which are rough, dark and red, and have an optical depth (TURN)3 x 10(' -6); these act as sources for the tinier grains. The halo is a crudely toroidal cloud of material, running from the ring's inner boundary roughly halfway down to the Jovian cloudtops. It is symmetric about the ring plane, and extends for (TURN)10('4) km above and below it. Its particle size distribution is not markedly different from the micron-sized population in the bright ring. In addition, we have discovered a much fainter ring, which extends outward from the main ring to an orbit of (TURN)210,000 km, though with ever-decreasing brightness. Its mean intensity is (TURN)5% that of the main ring, and its only notable feature is a (TURN)20% brightness enhancement at synchronous orbit.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1985
- Bibcode:
- 1985PhDT.........2S
- Keywords:
-
- Physics: Astronomy and Astrophysics;
- Halos;
- Imagery;
- Jupiter Rings;
- Planetology;
- Image Enhancement;
- Image Processing;
- Optical Density;
- Particle Size Distribution;
- Radii;
- Voyager 1 Spacecraft;
- Lunar and Planetary Exploration