Ring World 1. Mass EarthSaturn 195.2 (x 10 24 kg) 5.97568 2.

Ring World

1

Mass

Earth Saturn

1 95.2

(x 1024 kg) 5.97 568

2

Size

Earth Saturn

Radius 1 9.45

Equatorial 6378 60,268

Polar 6357 54,364

Oblateness 0.3% 9.8%

Look for the flattening in the next photo.

3

4

Earth Our Moon

5

Density

Earth Saturn

100% 12.5

kg/m3 5515 687

Saturn has the lowest density of all the planets and moons.

Saturn would float in water!

6

7

Large Magnetosphere

• Saturn’s magnetosphere is about 1/5th as large as Jupiter’s.– This is expected because Saturn has a

thinner conducting mantle of metallic H than Jupiter has.

• It’s 20x weaker than Jupiter’s field.– It’s actually only 68% as strong as Earth’s!

8

9

Magnetosphere

• Jupiter’s magnetosphere is tipped slightly to its rotation, and is complex in structure

• Saturn’s magnetosphere is aligned almost perfectly with its rotation (axisymmetric), and its structure is very simple.

• Interesting feature: a ring current.

10

Evidence for Saturn’s Magnetic Field! 11

Equatorial Ring Current

• Saturn’s moons Enceladus, Dione, and Tethys are enclosed in a torus of ions (like Jupiter’s Io).

• This torus is outside the major rings (but inside the thin, tenuous E ring).

• A current of about 10 million amps flows through this outer ring.

12

13

Chemical Composition

• 96.3% H 3.25% He (by volume)

• Traces of methane (CH4), ammonia (NH3), water, ammonium hydrosulfide (NH4SH)

• Like Jupiter, there is a mantle of metallic H under a gaseous H envelope.

• Rocky / metallic core

14

15

Saturn’s Orbit

• Average distance from the sun:

1.43 billion km (9.6 A.U.)

• Perihelion: 1.35 billion km

• Aphelion: 1.51 billion km

• Orbit Eccentricity: 0.056 (slightly more eccentric than Jupiter’s orbit)

16

Orbit (2)

• Orbital Period: 29.5 years– Orbital Velocity: 9.7 km/s

• Inclination of orbit to ecliptic: 2.5o

17

18

Saturn’s Rotation

• Rotational Period: 10.66 hours (10h 40m)

• Saturn has zonal winds, like Jupiter, but the colors are more muted.

• The rotational axis is tilted 26.7o to the ecliptic. This makes for a periodic tilt in the rings as viewed from the earth.

19

20

Notice the rotational storm.

21

A red oval similar to Jupiter’s GRS.22

23

apod.nasa.gov/apod/ap090111.html24

The Rings !

• 2 (3) rings visible to the naked eye.

– separated by visible gaps.

• 3 more rings visible telescopically

• A new ring appears to be forming!

25

26

Pan orbits within the Encke Division27

28

29

Movie

Dustyring“spokes”

30

Rings are Dynamic, not Static

• Dusty spokes indicate that the rings may be able to change on a short time frame.

• There are also periodic “ripples” in part of the rings…evidence of a collision between the rings & a comet or asteroid.

31

32

BraidedF ring

The ringisn’t reallybraided,but hasspiralsaround it.

33

Here’s a site with more info about the spiralaround the F ring.

http://www.aim.ufr-physique.univ-paris7.fr/CHARNOZ/homepage/SPIRAL/spiral_uk.htm

34

Shepherd Moons

• Collisions between ring particles should remove kinetic energy from some particles, transfer kinetic energy to others.

– Slower particles should fall into Saturn.– Faster particles should leave the ring.

– Net: the rings should spread out and dissipate.

35

The gravityof theshepherdmoonsfocuses therings.

36

37

Barelydiscerniblenew ring(with 2 newtiny moons)

38

The Larger Moons

• They’re all ice balls, but they’re not all the same.

• Mimas Enceladus Tethys• Dione Rhea Titan• Iapetus

• All of these moons are in synchronous rotation (leading vs. trailing hemisphere differences)

39

40

MimaswithHerschelCrater

Mimas isabout thesize ofOhio

1150 kg/m3

41

42

Enceladus

43

Bluish “tiger stripes”

South Pole

Geysers of water & water vapor erupt fromEnceladus’ south pole region.

Hot spots have been discovered here by Cassini.44

45

Tethys hasa giganticcanyonwhich nearlycircles themoon.

Ithaca Chasma

46

Dione, leading hemisphereat left, trailing at right.

47

Dione

Direction ofmovementthrough space.

48

Rhea

49

Rhea also hasthose strangelighter stripeson its trailinghemisphere.

50

Titan 5150 km diameter 1880 kg/m3

Ganymede 5262 km dia. 1940 kg/m3

How can Titan have a thick atmosphere, when Ganymede doesn’t?

Atmosphere of N2

heavily laden withhydrocarbons:methane ethane

Very smoggy

51

Titan hasa complexlayeredatmosphere

52

Titan’s atmosphere is 95% N2, 10X denser thanEarth’s, and extends 600 km above the surface.

53

54

Some liquidflows ontitan’ssurface.

55

The shoreline of an ethane lake.

56

The darker areas are lakesof liquid methane and ethane.

57

At Titan’s surface, theTemperature is about95K (-290oF)

58

59

Iapetussooty leading hemispherebright trailing hemisphere

equatorial ridge

What’s thesource ofthe soot?

60

Hyperion – a captured comet?apod.nasa.gov/apod/ap090118.html 61

Missions to Saturn

• Pioneer 11– Launched 1973, flyby 1979.– Transmitted low-resolution photos of Saturn,

rings, moons.

• Voyager 1– Launched 1977, flyby 1980– Transmitted 900+ photos of the moons.– Discovered complexity of rings & nature of

Titan’s atmosphere.62

Missions to Saturn (2)

• Voyager 2– Launched 1977, flyby 1981– 1150 photographs of the moons

• Cassini Orbiter with Huygens probe to Titan’s surface.– Launched 1997, arrived in orbit July 1, 2004.

63

Cassini’s Mission• Cassini is designed to photograph and

map Saturn & its moons in visible, infrared, and ultraviolet wavelengths.

• It has a magnetometer, magnetic imager, and plasma imager to closely study Saturn’s magnetic field.

• Huygens probe landed on Titan on January 14, 2005.

64

65

66

67

68

69

http://nssdc.gsfc.nasa.gov/planetary/factsheet/saturnfact.htmlhttp://hpd.botanic.hr/ast/astronomija/sunsust/saturn/saturn.jpghttp://media.nasaexplores.com/lessons/04-305/images/saturn-tub.jpghttp://saturn.jpl.nasa.gov/multimedia/images/saturn/IMG000476-br500.jpghttp://www.esa.int/esapub/bulletin/bullet92/images/b92kohf18.gifhttp://www-spc.igpp.ucla.edu/personnel/russell/papers/sat_mag.htmlhttp://www.gather.com/uploads/3096224743839048/fullhttp://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2176http://www.whfreeman.com/ENVIRONMENTALGEOLOGY/EXMOD36/F3622.JPGhttp://homepage.ntlworld.com/mjpowell/Astro/saturn-orbit-1993-2020.gifhttp://imgsrc.hubblesite.org/hu/db/1994/53/images/a/formats/full_jpg.jpghttp://pds.jpl.nasa.gov/planets/captions/saturn/redcloud.htmhttp://pds.jpl.nasa.gov/planets/captions/saturn/fring.htmhttp://science.nasa.gov/headlines/y2002/images/rings/ringnames_big.gifhttp://science.nasa.gov/headlines/y2002/12feb_rings.htmhttp://rst.gsfc.nasa.gov/Sect19/Sect19_18.htmlhttp://www.universetoday.com/am/uploads/2004-0909ring-full.jpghttp://hal.physast.uga.edu/~jss/1010/ch11/http://www.spaceflightnow.com/cassini/061011dring.htmlhttp://www.aim.ufr-physique.univ-paris7.fr/CHARNOZ/homepage/SPIRAL/spiral_uk.htmhttp://astrogeology.usgs.gov/Projects/BrowseTheSolarSystem/gifs/dione2.gifhttp://esamultimedia.esa.int/images/Science/huygens31150.jpg

http://esamultimedia.esa.int/images/cassini_huygens/PIA06983_H.jpghttp://antwrp.gsfc.nasa.gov/apod/image/0501/landing_huygens_01_h3.jpghttp://antwrp.gsfc.nasa.gov/apod/ap060131.htmlhttp://lexikon.astronomie.info/saturn/titan/FlugplanHuygens.htmlhttp://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1105http://www.windows.ucar.edu/tour/link=/saturn/space_missions.htmlhttp://saturn.jpl.nasa.gov/spacecraft/images/sc-components-litho.jpghttp://solarsystem.nasa.gov/multimedia/gallery/Cassini_Enc.jpg