# Presentation: 431283

## Slide 1

## 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

## Slide 4

## Main ring

- Dark side = High “phase angle”: emphasizes tiny dust grains

## “Halo”

- “Halo”

- “Gossamer ring” discovery

## Two “Gossamer” rings

- Dusty rings must be sustained by source bodies
- (seen or unseen)

## Slide 8

## A       B      C

- Encke Gap

- Cassini Division

- D

- F

- Lit side = Low “phase angle”: emphasizes large bodies

## E

- G

- Enceladus

- Earth!

- Unique high-phase view!

- F

## “Geysers” on Enceladus

- “Geysers” on Enceladus
- = the source of the E ring

## Cassini On-line Resources

- Cassini Main Site
- _[http://](http://saturn.jpl.nasa.gov/)__[saturn](http://saturn.jpl.nasa.gov/)__[.](http://saturn.jpl.nasa.gov/)__[jpl](http://saturn.jpl.nasa.gov/)__[.](http://saturn.jpl.nasa.gov/)__[nasa](http://saturn.jpl.nasa.gov/)__[.](http://saturn.jpl.nasa.gov/)__[gov](http://saturn.jpl.nasa.gov/)__[/](http://saturn.jpl.nasa.gov/)_
- The latest raw images (cool!)
- _[http://](http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm)__[saturn](http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm)__[.](http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm)__[jpl](http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm)__[.](http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm)__[nasa](http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm)__[.gov/multimedia/images/raw/index.cfm](http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm)_
- Imaging Team Web Site
- _[http://ciclops.org/](http://ciclops.org/)_

## The “Opposition Surge”on Saturn’s rings.

- The “Opposition Surge”on Saturn’s rings.
- This appears exactlyopposite to the directionto the Sun, at phaseangle 0°.
- The size of the surge isa measure of how rough the particles are.

## Slide 14

## gamma

- eta

- lambda

- epsilon

- beta

- alpha

- 6, 5, 4

- delta

- The main rings of Uranus
- Imaged by Voyager 2
- Low phase = big particles

## The rings of Uranus at high phase

-   > dust belts!

## Slide 17

## Uranus in HST

## Long exposures reveal rings

## Overlaying frames shows moons

## Processing shows new rings!

- Mab & the mu ring

- nu ring

## Slide 22

## Liberté

- Fraternité

- Egalité

- Courage

- Leverrier
- ring

- Adams
- ring

## Slide 24

## 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

## Enhanced Galileo image of Jupiter’s main ring

- A “wireframe” diagram showing vertical ripples in a ring

## 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.

- Color
- enhancement
- reveals “spiral”
-  structure.

- Perturbed
- central
- ringlet

## The discovery

- of Pan
- in a sequence
- of five
- Voyager images

## A spectacular

- view of
- the Pan wake
- from Cassini

- direction to Pan

## Pan Imaged at Fine Resolution by Cassini

## The Discovery of Daphnis in the Keeler Gap:

- The wake is highly distorted

## Fun with Rings (3)

- Saturn’s Pathological F Ring

## Ophelia

- Cordelia

- Two moons “shepherd” the
- epsilon ring of Uranus

## Pandora

- Prometheus

- Distant Voyager approach image:
- Is the F ring shepherded too?

## Saturn’s Famous

- “Braided” Ring!

## 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...

- 2007: A Good Yearahead 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

## 2003

- 2005

- 2007: Equinox!

- Edge-on viewing:
-  the main rings go dark
-  search for “shepherds”
-  see the dust rings better

## Slide 49

## Remember what Amalthea and Thebe do at Jupiter!

## December, 2007:

- the best ring viewing geometry
- till 2022!