Chapter 8 Jovian Planets Systems

1
Chapter 8Jovian Planets Systems

• Chapter Outline
• A Different Kind of Planet
• A Wealth of Worlds Satellites of Ice and Rock
• Jovian Planet Rings

3/21/2006 1014 AM
2
8.1 A Different Kind of Planet

• What are Jovian planets made of?
• What are Jovian Planets like on the inside?
• What is the weather like on Jovian planets?

3
Jovian Planets
4
Jovian Planet Formation

• Beyond the frost line, planetesimals could
  accumulate icy materials.
• Hydrogen compounds (H2O, CH4, NH3) were
  significantly more abundant than the rocky
  materials.
• Thus as Jovian planets grew larger they could
  capture more and more of the H and He gases until
  solar radiation expelled most of it into
  interstellar space.

5
What are Jovian planets made of?

• Jupiter and Saturn almost all H and He, very
  little metallic and rocky materials (less dense)
• Uranus and Neptune hydrogen compounds (water, methane, ammonia),
  with some metallic and rocky materials (more
  dense)

Why are they different?
6
Understanding Jovian Planet Sizes and Densities
How radius of a hydrogen/helium planet depends on
the planets mass.
Adding mass eventual compresses the planet to
higher densities.
7
Jupiters Interior Structure
Pressure
Temperature
Density
8
Interior Structures of the Jovian Planets
All four have cores equal to about 10 Earth
masses of rock, metal, and hydrogen compounds.
They differ primarily in the hydrogen/helium
layers surrounding the core.
9
Jupiters Magnetosphere
Artist Conception
Magnetic Field Lines
Io
Europa
Galilean Satellites
Charged Particle Belt Formed by Io
Ganymede
Callisto
10
Magnetic Fields Conformation of Interior
Structure

• Magnetic axis inclined to rotational axis
• Jupiter 10o, Saturn 0o, Uranus 59o, Neptune
  47o, Earth 10o
• Jupiter, Saturn, Neptune magnetic axis oriented
  opposite that of Earth
• Magnetic center not geometric center for Uranus
  and Neptune

11
Differential Rotation
Polar rotation period 9h 55m 41s
Equatorial rotation period 9h 50m 28s

• Solid body rotation - particles far from axis of
  rotation have same rotation period as ones near
  to axis
• Terrestrial planets
• Differential rotation - particles far from axis
  of rotation have different rotation periods from
  ones nearer to axis
• Jovian planets

Jupiter rotates differentially
12
Composition of Jovian Atmospheres
13
Cloud Patterns in Jovian Atmospheres
14
Dynamics of Jupiters Atmosphere

• Three features
• Light-colored zones
• Dark-colored belts
• Light and dark ovals
• Observed streaming in atmosphere
• Complex interactions on boundaries between belts
  and zones
• Note waves on the boundaries between belts and
  zones

Light-colored zone
Light and dark ovals
Dark-colored belt
15
Jupiters Great Red Spot

• Great Red Spot has been observed since 1665
• Thermally driven storm
• Vortexing motions
• Smaller ovals observed to move around spot
• Smaller ovals are also vortex motion

?20,000 km
?10,000 km
16
Jupiters Atmospheric Structure

• Earths rotation makes storms spin.
• Jupiters fast rotation stretches storms into
  bands that surround the planet.
• High east/west winds (up to 400 km/hr).

17
Jupiters Belts and ZonesWarm and Cool Material
18
Vertical Structure in Jupiters Atmosphere
Probable white-colored clouds (high altitude)
composition is frozen NH3 and H2O crystals
Probable brown, red, and orange-colored cloud
(lower altitude) composition is frozen sulfur
compounds, possibly phosphorus
19
Jupiters Atmospheric Structure
Temperature and pressure profiles from radio and
infrared measurements indicating 3 major cloud
layers. Galileo spacecraft data suggests cloud
layers do not uniformly cover planet. There are
some relatively clear areas.
20
Saturns Atmosphere
Polar rotation period 10h 40m

• Differential rotation as does Jupiter
• Atmosphere does have belts and zones
• Hazy above cloud layers make banded structure
  less distinct

Equatorial rotation period 10h 14m
21
Uranus Atmosphere
Infrared

• From great distances appears as bland,
  featureless, blue-green planet
• Higher abundance of CH4 than Jupiter and Saturn
• Does have clouds, but high altitude haze obscures
• NH3 H2O frozen out, thus no NH3, NH4SH, or H20
  clouds

Visible
Cloud Features
22
Neptunes Atmosphere
Exaggerated Color Contrast Image

• Similar composition to Uranus
• Clouds more visible than Uranus

Great Dark Spot
Methane ice crystal clouds
Cirrus Clouds
South Pole
Multi-Spectral Visible Image
23
8.2 A Wealth of Worlds Satellites of Ice and Rock

• What kinds of moons orbit the Jovian planets?
• What makes Jupiters Galilean satellites unusual?
• What makes Titan different from other satellites?
• Why are small icy moons more geologically active
  than small rocky planets?

24
Why are the largest and the majority of the
naturally occurring satellites associated with
the Jovian planets?

• The availability of the icy planetesimals being
  more numerous in the vicinity of the Jovian
  planets should have lead to them having more
  satellites.
• The strong gravitational fields of the Jovian
  planets should have enhanced their ability to
  form and retain more and larger satellites.

25
Large and Medium Satellites

• Formed in orbit around Jovian planets.
• Circular, equatorial orbits with satellite moving
  in same direction as planets rotation.

26
Galilean Satellites of Jupiter
Io
Ganymede
Callisto
Europa
27
What makes Jupiters Galilean satellites unusual?

• Io has volcanoes.
• Europa may have an ocean under its ice.
• Ganymede and Callisto may also have sub-surface
  oceans.

but theyre so small comparable to the Moon and
Mercury! Shouldnt they be cold and dead?
28
Galilean Satellite - Io
29
Since Io is about the size of the Moon, should
not it have lost its primeval heat long ago as
did the Moon? So why is the interior thought to
be molten?

• Some radioactive materials may provide some
  heating of the interior by natural radioactive
  decay (fission).
• Primary heating source is likely to be
  gravitational/mechanical through frictional
  dissipation of mechanical energy provided by
  Jupiter.

30
Tidal Heating
Io is distorted and stretched as it orbits Jupiter
But why is its orbit so elliptical?
31
Orbital Resonances
Every 7 days, these 3 satellites line up as
shown.
Gravitational tugs add up over time, making all 3
orbits elliptical.
32
Galilean Satellite - Europa

• Numerous streaks and cracks are typically 20 to
  40 km wide
• Upper inset shows details of dust covered surface
• Lower inset shows details of crater

33
Europa Also Heated by Tidal Friction
34
Galilean Satellite - Ganymede

• Huge, dark, circular region called Galileo Regio,
  remnant of ancient crust
• Lighter areas are younger than dark areas
• Bright shiny areas probably indicate presence of
  water ice

35
Galilean Satellite - Callisto

• Numerous craters on surface
• Series of circular rings on left marking region
  called Valhalla
• Numerous craters suggest surface is geologically
  inactive

36
Saturns Titan
Hubble Space Telescope infrared image showing
surface features
This image was returned 1/14/ 2005, by ESA's
Huygens probe after its successful descent to
land on Titan.

• Thick opaque atmosphere of N2, CH4, and other
  hydrocarbons

Enceladus Voyager 2 Visible Image
37
Saturns Medium-Sized Satellites
38
8.3 Jovian Planet Rings

• What are Saturns rings like?
• Why do the Jovian planets have rings?

39
Why would a ring system form about each of the
Jovian planets and not another satellite?

• Availability of particles at the time of
  formation and strong gravitational fields of
  Jovian planets account for ring system.
• Close proximity of the particles to the planet
  must be part of the answer as to why the
  particles did not coalesce into another satellite.

40
Saturns Ring System

• 1995 rings almost edge-on to Earth
• Note thinnest of rings

Hubble Visible Image
Titan

• Above sizes and designations for major rings
• Cassini division is 4500 km apparent gap between
  B ring and A ring
• Note rings not solid as Saturn can be seen
  through rings

Tethys
3 Months Later
Dione
41
Numerous Thin Ringlets in Saturns Ring System
Computer Enhanced Ultraviolet and Visible Image
Voyager 2 Visible Image

• Ring particles vary in size from 1 cm to 5 m
• Most abundant are 10 cm size particles
• Constitutes small amount of matter (100 km
  satellite)
• Ring particles are dirty ice fragments from
  formation period (scattering)
• Dust particles fill Cassini and Encke divisions

42
Jupiters Ring System

• Rings closer to planet than satellites
• Composed of tiny rock fragments (not highly
  reflecting)
• Probably being continually replenished by
  material from Io
• Radiation pressure from Jupiter and Sun should
  move them away

6000 km
Sharp outer edge
Fuzzy inner edge with material extending down to
cloud tops
Voyager 2 Visible Image
43
Uranus Ring System
HST Visible Image
Voyager 2 Visible Image
Looking back toward Sun shows fine-grain dust
scattering Streaks are star trails seen through
rings
44
Neptunes Ring System

• Thin, dark ring system similar to that of Uranus
• Two main rings
• Faint inner ring
• Particle sheet extends toward planet

45
The Big Picture

• Jovian planets may lack solid surfaces on which
  geology can work, but they are dynamic bodies
  with winds, huge storms, strong magnetic fields,
  and interiors in which materials behave in
  unfamiliar ways.
• Despite their relatively frigid temperatures,
  many Jovian satellites are geological active by
  virtue of their icy compositions. Ironically, it
  was cold temperatures in the solar nebula that
  led to icy compositions and hence geological
  activity.
• Ring systems owe their existence to small
  satellites formed about the Jovian planets
  billions of year ago. The rings are composed of
  particles liberated from those satellites
  surprisingly recently.
• Understanding the Jovian planets forced us to
  modify many of our earlier ideas, in particular
  by adding the concepts of ice geology, tidal
  heating, and orbital resonances.