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The Giant Planets Jovian Planets
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The Giant Planets Four giant (or “Jovian”) planets:
Planet Distance Orbital from Sun Period Jupiter AU yrs Saturn Uranus Neptune All have: rings one or more large satellites many small satellites (probably lots undiscovered) Jovian Planets
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Exploration of the Giant Planets
Most information from space probes Moons, rings, weather, magnetic fields Technically difficult Far away, long flight times Hazards: meteors, cold, radiation Jovian Planets
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Past and current spacecraft
Pioneer 10 and 11 (early 1970s) Voyagers 1 and 2 (1977 to 1989) Galileo (Jupiter and moons) Atmospheric probe Dec to 21 Sept. 2003 Cassini (Saturn and rings) At Saturn since 2004 Huygens atmospheric probe to Titan (largest moon)—landed Jan. 14, 2005 Jovian Planets
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Jupiter, the Giant Jovian Planets
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Jupiter: largest of all
Mass: 318 times Earth Radius: 11 times Earth (flattened at poles) Density: 1.3 gm/cm3 (Earth: 5.5) Mostly hydrogen, helium, little rock or iron Rotation: 10 hours (faster at equator than at poles, not a solid surface) Jovian Planets
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Jupiter's atmosphere Visible disk is clouds
Frozen ammonia plus hydrocarbons (“smog”) Pattern of light, dark bands Driven by internal heat (convection and rotation) Oval patterns are storms like hurricanes Jovian Planets
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a true-color picture of Jupiter
light and dark bands in latitude (along the direction of rotation) are smog-like clouds ovals are giant storms like hurricanes stretched out by rapid rotation Jovian Planets
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(more on Jupiter’s atmosphere)
The Great Red Spot First seen in 1630, little changed since 40,000 km long, 14,000 km wide Red due to hydrocarbons and phosphorus Jovian Planets
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The Great Red Spot (a long-lived storm)
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Figure 8.10a enhanced color image from your textbook
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(more on Jupiter’s atmosphere)
Composition of atmosphere Voyager, and esp. Galileo probe Element % mass Hydrogen 86 Helium 14 Others (ammonia, methane) Very much like Sun’s composition Jovian Planets
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Interior Structure of Jupiter
Three clues: Average density: 1.3 gm/cm3 Composition like Sun Observations of infrared light: Jupiter radiates almost twice the energy it receives from Sun, so Jupiter must have internal heat source Jovian Planets
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Interior Structure (cont.)
Internal layers (best guess model) Atmosphere (1000 km thick) includes the clouds, what we see Liquid hydrogen + helium (20,000 km) Metallic hydrogen (35,000 km) Iron and rock core (10-20 times Earth’s mass) Jovian Planets
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A model of Jupiter’s interior 1 bar is the pressure
Figure 8.3 (density of liquid water) 1 bar is the pressure of the air we breathe A model of Jupiter’s interior
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A model of Jupiter’s interior
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Jupiter’s magnetic field and radiation belts
Space probes found strong field, 10 times Earth’s Generated by metallic liquid hydrogen layer and rapid rotation (a “dynamo”) Makes big, intense radiation belts Electrons and protons from Sun trapped on magnetic field Hazard to spacecraft like Galileo Jovian Planets
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Jupiter’s radiation belt and magnetic field
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Jupiter’s satellites and ring
At least 63 moons, 1 ring known 4 largest seen by Galileo (in 1610) Voyager, Galileo probes found great variety Jovian Planets
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Jupiter’s Galilean satellites
Satellite Period Density Mass (days) (gm/cm3) (Moon=1) Io Europa Ganymede Callisto Composition varies a lot (note range of densities) Jovian Planets
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The Galilean Satellites and the Great Red Spot
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The Galilean Satellites (in order from Jupiter)
Io Mostly rock (note density) Active volcanoes! (molten sulfur) Heated by tidal forces from Jupiter Elliptical orbit, gets squeezed each time Surface: very young, constantly renewed by volcanic outflows (seen by Galileo spacecraft) Jovian Planets
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Slides of Io Full-view images Closeup of active volcano Lava flow
Enhanced and true color Lava flow Active eruption; note glowing lava Left, Io in eclipse with glowing gases over active volcanoes Jovian Planets
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Images of Io from Galileo spacecraft
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Active eruption; note glowing lava
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Galilean satellites (cont.)
Europa Mostly rock (note density) Thin, icy crust, with long complex cracks Surface: rel. young, few impact craters Eroded since 3 billion years ago Galileo spacecraft found evidence of liquid water ocean under icy crust! Possible life in the water??? (NASA wants to go ice fishing) Jovian Planets
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Slides of Europa Enhanced color view Closeup of crossing cracks
Note many long cracks Closeup of crossing cracks Super closeup, looks like ice flows Who lost a mitten? What made this structure? Chaotic icy blocks Two models of Europa’s inside Warm icy slush (a giant Eegee’s ! ) Real liquid water under ice Jovian Planets
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Enhanced color view of Europa Note many long cracks
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Closeup of crossing cracks
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Super closeup, looks like ice flows
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Who lost a mitten? (What made this structure?)
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Chaotic icy blocks Jovian Planets
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Two models of Europa’s inside (1) Warm icy slush (a giant Eegee’s
Two models of Europa’s inside (1) Warm icy slush (a giant Eegee’s ! ) (2) Real liquid water under ice Jovian Planets
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Continuing our tour of Jupiter’s Galilean satellites… Io Europa
Ganymede Callisto Jovian Planets
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Galilean satellites (cont.)
Ganymede Largest moon in solar system Density implies Rocky core, size of our Moon Thick mantle of water ice (brittle, because very cold: C) 1/3 of surface heavily cratered Old, over 4 billion years Rest smooth or grooved terrain (but ice, not rock) Jovian Planets
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Ganymede: a strange mix of dark, light areas
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Grooves in surface of Ganymede—”tectonic” activity in ice!
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Galilean satellites (cont.)
Callisto Icy, like Ganymede Heavily cratered over whole surface (shallow craters in ice, not rock) Unchanged since end of heavy impact cratering 4 billion years ago Oldest surface in Solar System Atmospheres No atmospheres in outer 3 Galilean moons Io has thin atmosphere of volcanic gases, with sulfur compounds Jovian Planets
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Callisto, cratered all over-- so entire surface is old, never melted
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Slides of Ganymede, Callisto, and the Ring
Strange mix of dark, light areas Callisto, cratered all over Entire surface is old, never melted Portraits of the Galilean satellites In order of size: Ganymede, Callisto, Io, Europa Ring, backlit by Sun Jovian Planets
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Portraits of the Galilean satellites In order of size: Ganymede Callisto Io Europa
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