Saturn Astronomy 311 Professor Lee Carkner Lecture 18

Which of the following is a major component of Jupiter’s clouds? a)Water b)Ammonia c)Molecular hydrogen d)a and b only e)a, b, and c

In what region does Jupiter generate its strong magnetic field? a)Rock/ice core b)Liquid metallic hydrogen mantle c)Molecular hydrogen atmosphere d)Dust ring e)Alternating cloud bands

What causes the vertical motion of Jupiter’s belts and zones? a)Convection b)Rotation c)Ionization d)The Coriolis force e)Liquid metallic hydrogen

As we go deeper into Jupiter, we find, a)The temperature increases b)The colors of the clouds change c)The composition of the clouds change d)b and c only e)a, b, and c

Saturn -- King of the Titans   He was overthrown by Jupiter who became king of the gods  Saturn’s symbol is the sickle

Viewing Saturn from Earth   First viewed through a telescope by Galileo   Modern telescopes reveal a series of rings and cloud patterns in Saturn’s atmosphere

Saturn Facts  Size: 9.5 Earth diameters   Orbit: 9.5 AU   Description: smaller, more distant Jupiter with rings

Viewing Saturn from Space   Hubble Space Telescope has provided many images   Orbiting Saturn to study it long term  Dropped a probe (Huygens) into Titan’s atmosphere

Path of Cassini

Saturn’s Atmosphere  Saturn has belts, zones, ovals and storms, but they are less distinct than on Jupiter   Nothing like the Great Red Spot   Saturn sometimes has storms that burst up from below

Composition of Atmosphere  We believe that Saturn has an atmospheric structure similar to Jupiter’s   Middle layer of Ammonium Hydrosulfide (NH 4 SH)   We don’t see all of the layers as clearly as we do on Jupiter

Saturn’s Dullness  The temperature of Saturn’s atmosphere increases more slowly with depth than Jupiter because:   Due to weaker gravity the layers are more spread out  As a result    Upper layers obscure the deeper layers

Saturn and Jupiter’s Atmospheric Structure

Saturn’s Heat   Saturn is smaller than Jupiter and should have radiated much of its heat away by now   Theory: the helium condensed into droplets and fell towards the core liberating gravitational energy   Calculations seem to support this

Saturn’s Interior  Saturn has a very low density (690 kg/m 3 )   This means it must have a large core (26% of the mass)   Saturn is much less massive than Jupiter so there is less gravity to compress the hydrogen   Due to slower rotation, less liquid hydrogen and blocking of charged particles by the rings

Internal Structure of Jupiter and Saturn

Saturn’s Rings  Saturn’s rings appear very bright but very thin from Earth   Rings reflect 80% of light that hits them   The inner rings moves faster than the outer rings   Size = 1cm to 5m (average ~10 cm)

Rings and Tides   This is the region where the tidal force pulling the material apart is stronger than the gravitational force holding it together

Structure of the Rings   Rings are separated by gaps or divisions with relatively few particles   The size and composition of particles vary from ring to ring   F ring has many small, dark particles

Diagram of Saturn’s Rings

Moons and the Rings  Several moons have orbits within the rings   Moons may also be a source of ring material  Examples of moons effecting the rings:   The Encke gap has a small moon, Pan, in it 

Next Time  Read Chapter

Summary  Saturn is the second largest planet and the second closest gas giant to Earth  Saturn is similar to Jupiter with key exceptions mostly due to less mass and smaller gravity  cloud layers are more spread out in depth  less distinct cloud bands  larger core  less liquid metallic hydrogen

Summary: Rings  Made up of many distinct rings and ringlets  Composed mostly of icy particles of various sizes and reflectivity  Ring structure shaped by moons  Rings cannot form a larger body due to tidal forces