The Giant Planets Jovian Planets

The Giant Planets Four giant (or “Jovian”) planets: Planet Distance Orbital from Sun Period Jupiter 5 AU 12 yrs Saturn 9 29 Uranus 19 84 Neptune 30 164 All have: rings one or more large satellites many small satellites (probably lots undiscovered) Jovian Planets

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

Past and current spacecraft Pioneer 10 and 11 (early 1970s) Voyagers 1 and 2 (1977 to 1989) Galileo (Jupiter and moons) Atmospheric probe Dec. 1995 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

Jupiter, the Giant Jovian Planets

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

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

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

(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

The Great Red Spot (a long-lived storm) Jovian Planets

Figure 8.10a enhanced color image from your textbook

(more on Jupiter’s atmosphere) Composition of atmosphere Voyager, and esp. Galileo probe Element % mass Hydrogen 86 Helium 14 Others 0.1 (ammonia, methane) Very much like Sun’s composition Jovian Planets

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

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

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

A model of Jupiter’s interior Jovian Planets

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

Jupiter’s radiation belt and magnetic field Jovian Planets

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

Jupiter’s Galilean satellites Satellite Period Density Mass (days) (gm/cm3) (Moon=1) Io 1.6 3.4 1.2 Europa 3.6 3.0 0.7 Ganymede 7.2 1.9 2.0 Callisto 16.7 1.8 1.5 Composition varies a lot (note range of densities) Jovian Planets

The Galilean Satellites and the Great Red Spot Jovian Planets

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

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

Images of Io from Galileo spacecraft Jovian Planets

Active eruption; note glowing lava Jovian Planets

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

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

Enhanced color view of Europa Note many long cracks Jovian Planets

Closeup of crossing cracks Jovian Planets

Super closeup, looks like ice flows Jovian Planets

Who lost a mitten? (What made this structure?) Jovian Planets

Chaotic icy blocks Jovian Planets

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

Continuing our tour of Jupiter’s Galilean satellites… Io Europa Ganymede Callisto Jovian Planets

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: -130 C) 1/3 of surface heavily cratered Old, over 4 billion years Rest smooth or grooved terrain (but ice, not rock) Jovian Planets

Ganymede: a strange mix of dark, light areas Jovian Planets

Grooves in surface of Ganymede—”tectonic” activity in ice! Jovian Planets

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

Callisto, cratered all over-- so entire surface is old, never melted Jovian Planets

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

Portraits of the Galilean satellites In order of size: Ganymede Callisto Io Europa Jovian Planets