The Fathers of the Gods: Jupiter and Saturn

Transcription

1 The Fathers of the Gods: Jupiter and Saturn

2 Learning Objectives! Order all the planets by size and distance from the Sun! How are clouds on Jupiter (and Saturn) different to the Earth? What 2 factors drive weather on the Gas Giants?! Compare and contrast the Great Red and White Spots! How does Jupiter s interior make a strong magnetic field? Does Jupiter s gravity and magnetism affect its moons?! Compare Jupiter and Saturn to each other and to Earth (size, seasons, interior, atmosphere, magnetic field)! Compare the Galilean moons to Titan and Enceladus. Each has one characteristic that makes it special! What are Saturn s rings made of? Is Saturn the only planet with rings?

3 The Outer Planets Inner Planets: Terrestrial or rocky Outer Planets: Jovian or Gas Giants

4 Jupiter Facts! Jupiter has at least 69 moons, the 4 most massive ( the Galilean Moons ) were discovered by Galileo Radius 11.2 Earth Surface gravity 2.5 Earth Mass 318 Earth Distance from Sun 5.2 AU Eccentricity Tilt 3.1 Year 11.9 Earth years Solar day 9 hrs 56 mins

5 Jupiter, King of the Planets! An atmosphere unlike Earth s! 90% Hydrogen, 10% Helium, ~0.3% other stuff! Similar to the Sun s composition! Rich chemistry! 0.3% contains methane, ammonia, other hydrocarbons, water, etc.! mph winds are commonplace! Incredible pressures! Increasing temperatures with depth

6 Driving Jupiter s Weather! On Earth, solar heating drives weather! On Jupiter, internal heat drives weather! Jupiter radiates ~70% more heat than it receives from the Sun! This heat is from Jupiter contracting under its own gravity! Convection then leads to cloud bands! Jupiter s strong rotation produces compact bands parallel to Jupiter s equator

7 The Outer Atmosphere! Watch the motion of the clouds:

8 The Great Red Spot! A huge storm 16,000 km across! A little larger than the Earth! Probably first observed over 300 years ago Cassini images Voyager 1 image

9 Other storms on Jupiter! Jupiter s poles are covered by constant storms! Many cyclones are visible in this (enhanced color) image of Jupiter s south pole from the Juno mission! The largest are about 1000 km in diameter J. Spencer Juno image

10 Jupiter s Interior! Average density only ~30% greater than water! ~25% that of the Earth s average density! By 20,000 km below the surface, the pressure is 3 million times that on the Earth s surface! Hydrogen is a liquid metal at this pressure! Core of rock & ice ~10-50 Earth masses

11 Jupiter s Magnetosphere! Liquid metal hydrogen generates a magnetic field! 14x stronger than the Earth s field! Over 4 million km across! A ring of ionized (electrically charged) particles surrounds Jupiter! These particles are stripped from Jupiter s moon Io by Jupiter s very powerful magnetic field

12 Saturn Facts! Saturn has at least 62 moons Equatorial radius 9.45 Earth Surface gravity 1.06 Earth Mass 95.2 Earth Distance from Sun 9.55 AU Eccentricity Tilt 26.7 Year 29.5 Earth years Sidereal day 10 hrs 33 mins

13 Driving Saturn s Weather! Like Jupiter, Saturn s atmosphere is mostly hydrogen and helium! As on Jupiter, Saturn s internal heat drives weather!saturn radiates over twice as much energy back into space as it receives from the Sun! Like Jupiter, Saturn is still contracting!as it contracts, heat is produced! As on Jupiter, storms are produced between cloud bands!no long-lasting storm like the Great Red Spot

14 The Great White Spot! A seasonal storm!!unlike Jupiter, Saturn has seasons! An ammonia bubble that forms in summer in Saturn s northern hemisphere! Lasts a few months!gets wrapped around the planet by the equatorial winds

15 Saturn s Interior! Similar structure to Jupiter!But Saturn is less massive, so less selfgravity!the interior is less compressed! Liquid metallic hydrogen creates a magnetic field!but not a strong one!slightly weaker than the Earth s field

16 !Jupiter has over 69 moons! Most are small! Some are captured asteroids!the 4 largest are the Galilean moons! Io, Europa, Ganymede and Callisto! Discovered by Galileo (one of the first uses of the telescope as a tool in astronomy) Jupiter s Moons Io Europa Ganymede Callisto

17 All Stirred Up! The Galilean moons have weak magnetic fields! Tidal and magnetic forces from Jupiter stir the interior of Jupiter s moons! Leads to warm & liquid interiors! Liquid conducting cores + rotation = magnetic fields! Also, this heating is what makes Io volcanic and allows water to stay in liquid form under Europa s surface

18 ! The innermost Galilean moon! The most volcanically active body in the Solar System! Volcanoes spew molten sulfur-loaded magma! Constantly repaved surface - very few impact craters Io Pillan Patera eruption Before & after

19 Europa! Icy crust ~10 to 30 km thick! Cracks and fissures on the surface likely some upwelling of water in impact craters! Evidence for a deep (~100 km) liquid water ocean beneath the crust Galileo Spacecraft

20 Ganymede! Largest moon in the Solar System! Partly ancient surface, partly younger surface! Younger surfaces are about the age of the Moon s maria! Compared to our Moon:! 50% larger! That s 10% larger than Mercury!! 100% more massive! 40% less dense! Interior more differentiated than Callisto, probably has an iron core

21 Callisto! Farthest of the Galilean Moons from Jupiter! Ancient surface, covered with craters! Compared to our Moon:! 40% larger! About Mercury s size! 50% more massive! 45% less dense! Surface is made of dirty ice! Interior is rocky, mixed with ice

22 Saturn s Famous Rings! Two main rings! (A and B)! Several fainter rings! (C through G)! The rings are thin! Only roughly tens to hundreds of meters thick! Made of ice-covered rocks and ice pellets! Note that Jupiter also has a weak ring system! In fact, all of the Gas Giants have rings

23 Titan! Saturn s largest moon! Bigger than Mercury! The second largest in the Solar System! Dense nitrogen and methane atmosphere (like smog)! The only moon in the Solar System to have a dense atmosphere! Liquid/ice hydrocarbons?! Organic compounds > life?! Probably not too cold: 95 K! May be a freeze of the chemical composition of the ancient Earth

24 Enceladus! Saturn s Sixth-largest moon! About 10x smaller in radius than Titan! Covered in ice! Smoothness suggests that ice in Enceladus southern regions is recently deposited! Geologically active! Dozens of water-rich geysers venting from beneath the surface!

25 Next Time The Edge of Town