The Jovian Planets. Saturn. Jupiter. Small Core /Atmosphere Ratio Rings Lots of Satellites

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1 Jupiter Saturn The Jovian Planets Small Core /Atmosphere Ratio Rings Lots of Satellites Uranus Neptune

2 Spacecraft Missions to the Jovian Planets Three Major Missions Pioneers 10 & 11 (launched 1972) Voyagers 1 & 2 (launched 1977) Galileo (launched 1989) Difficulties with sending probes to Jovian planets Energy source: solar panels + internal radioactive generators needed Distance from Earth: autonomous Destruction of spacecraft by debris: asteroids, rocks, etc. Trajectory: gravity assisted

3 Flight Paths of Voyager Spacecraft Gravity-assisted Trajectories

4 Trajectory video Cassini Spacecraft (arrival date to Saturn 2004)

5 Where are the Voyager Spacecraft? Deep Space Network Antenna locations Voyager 1 & 2 continue to transmit signals back to Earth They are continuously monitored by the Deep Space Network

6 Present mission Find the edge of the Solar System (Video)

7 The Jovian Planets How do we determine the nature of their interiors? Mass, radius, rotation rate, heat balance, atmospheric composition, gravitational effects on moons Composition Primarily Hydrogen & Helium, plus methane, ammonia, water ice, etc Dense core: required to account for gravitational field; composed of things denser than Hydrogen & Helium (Silicon, metals, heavy volatiles?) Note: The behavior of Hydrogen & Helium at high temperatures & pressures is not well understood

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9 Sizes of Jovian planets compared to the Earth 317 M earth 90 M earth 14 M earth 17 M earth

10 Properties of Jupiter Note: Hydrogen and Helium are colorless. Composition: 75% hydrogen, 24% helium + methane, ammonia, water ice Average Distance from the Sun: 0.7 light hours Rotation Rate 9 h 55 m 30 s Magnetic Field 9 h 50 m 30 s Equatorial Clouds 9 h 55 m 41 s High Latitude Clouds Orbital Period: 11.9 Earth years Axis Tilt: 3.1 Number of Moons: ~ 61

11 Moons are being found at a regular rate around the Jovian planets Technique is similar to Kuiper Belt search

12 The moon Io and Jupiter

13 Properties of Saturn Note: tan smog that overlies clouds below gives Saturn its color. Average Distance from the Sun: 1.3 light hours Rotation Rate 10 h 39 m 24 s Magnetic Field 10 h 14 m Equatorial Clouds 10 h 40 m High Latitude Clouds Orbital Period: 29.5 Earth years Axis Tilt: 27 (i.e., Seasons: UV + Methane Ethane in the Summer Number of Moons: ~ 31 Equator is 10% wider than pole-to-pole

14 The Jovian planets have equatorial bulges Rotation Rates ~ hours Gravity makes planets spherical Rotation makes planets bulge at the equator (Note: This keeps rings/satellites aligned with equator)

15 Jupiter & Saturn are about as large as planets can be

16 Internal Heat Sources Jupiter & Saturn radiate twice as much heat as they receive from the Sun Earth radiates 0.005% as much energy as it receives from the Sun Source of heat from Jupiter is the slow contraction of the planet Gravitational potential energy kinetic energy thermal energy Source of heat from Saturn is Helium rain At lower temperature & pressure of Saturn, liquid helium does not dissolve with liquid hydrogen Deficit of Helium relative to Hydrogen has been measured in the outer atmosphere of Saturn

17 Probing Jupiter s Atmosphere The Galileo Probe (video)

18 1995: Galileo probe dropped into Jupiter s atmosphere

19 (UV) Troposphere: turbulent clouds due to the Greenhouse effect cold enough for water to condense, etc

20 Jovian Atmosphere Comparison

21 Internal structure of Jupiter

22 Belts & Zones Strong Coriolis forces divide circulation cells into bands Convection results in bands of different color Zones: rising, cooling air out of which ammonia condenses into clouds Belts: falling air depleted in clouds; allows clouds below to be seen

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24 The Great Red Spot Storm that has persisted for at least 300 years Size: twice as wide as the Earth Why are such storms so long-lived? No solid surface to sap away energy (as happens on the Earth)

25 Magnetic Fields

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27 Auroras of Jupiter Ultraviolet Flux tube connecting satellites to Jupiter

28 Rings Composition: mixture of rocks of varying sizes comprised mostly of water ice (high albedo) Dimensions of Saturn s rings: 270,000 km x 10s of meters Roche zone: tidal forces ~ binding gravitational forces Note: smaller rocks are held together by gravitational & electrostatic forces, & thus can survive

29 Jupiter s Rings Jupiter s rings are less prominent than Saturn s Why? Smaller particles

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31 Features in Rings Gaps are present in the rings. They are created by Gap Moons that nudge particles out of particular orbits Spokes: particles levitated out of ring plane by forces associated with the magnetic fields

32 Origin of Rings Moon that strayed too close Tidal forces prevented a Moon from ever forming there

33 Formation of Jovian Planets & Satellites Ice & Rock cores build Mass ~ 10 Earth Masses Hydrogen & Helium from surrounding solar nebulae were gravitationally captured Planets that are massive & cold enough can retain hydrogen & helium Solid grains in surrounding nebula form satellites