Jupiter (Galileo) Saturn (Cassini) Uranus (Hubble) Neptune (Voyager)
Everything You Need to Know about Ring Dynamics Newton: Force = Mass x Acceleration Law of Gravity Collisions Light-scattering Physics
Main ring Dark side = High “phase angle”: emphasizes tiny dust grains
“Halo” “Gossamer ring” discovery
Dusty rings must be sustained by source bodies Two “Gossamer” rings Dusty rings must be sustained by source bodies (seen or unseen)
A B C D F Encke Gap Cassini Division Lit side = Low “phase angle”: emphasizes large bodies
Earth! Enceladus F Unique high-phase view! G E
“Geysers” on Enceladus = the source of the E ring
Cassini On-line Resources Cassini Main Site http://saturn.jpl.nasa.gov/ The latest raw images (cool!) http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm Imaging Team Web Site http://ciclops.org/
The “Opposition Surge” on Saturn’s rings. This appears exactly opposite to the direction to the Sun, at phase angle 0°. The size of the surge is a measure of how rough the particles are.
The main rings of Uranus Imaged by Voyager 2 Low phase = big particles epsilon lambda delta gamma eta beta alpha 6, 5, 4
The rings of Uranus at high phase > dust belts!
Uranus in HST
Long exposures reveal rings
Overlaying frames shows moons
Processing shows new rings! nu ring Mab & the mu ring
Adams ring Leverrier ring Fraternité Egalité Liberté Courage
Neptune’s Changing Arcs The arcs can now be detected by Hubble and ground-based telescopes. Since 1989, the leading arcs have advanced forward and faded. Gravity effects of the nearby moon Galatea help to confine the arcs …but the model is in trouble!
Fun with Rings (1) Vertical Ripples
D ring ripples that have been winding up since 1984!
Fun with Rings (2) Satellite “Wakes”
Wavy edge of Encke Gap suggests an embedded moon. Perturbed central ringlet Color enhancement reveals “spiral” structure.
The discovery of Pan in a sequence of five Voyager images
direction to Pan A spectacular view of the Pan wake from Cassini
Pan Imaged at Fine Resolution by Cassini
The Discovery of Daphnis in the Keeler Gap: The wake is highly distorted
Saturn’s Pathological F Ring Fun with Rings (3) Saturn’s Pathological F Ring
Ophelia Cordelia Two moons “shepherd” the epsilon ring of Uranus
Distant Voyager approach image: Is the F ring shepherded too? Pandora Prometheus
A Selection of Cassini Images
Prometheus produces a “wake” pattern just like Pan
The aftermath of a ring impact?
A recent, new feature 200 km inward from the central ring
2007: A Good Year ahead for Ring Science…
Cassini Extended Mission July 2008–June 2010 Sample Tour Science planning is proceeding. Note that this period includes the equinox on August 11, 2009!
New Horizons at Jupiter February 28, 2007
The first images of Jupiter from New Horizons Range is 1 AU
Sample planned images during the New Horizons flyby