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Transcript
The Fathers of the Gods: Jupiter and Saturn 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 Jupiter’s Galilean moons and Saturn’s moon Titan. Each has one characteristic that makes it special What are Saturn’s rings made of? Is Saturn the only planet with rings? The Outer Planets Inner Planets: “Terrestrial” or “rocky” Outer Planets: “Jovian” or “Gas Giants” Jupiter Facts! Jupiter has over 65 moons, the 4 most massive (“the Galilean Moons”) were discovered by Galileo Radius Surface gravity Mass Distance from Sun Eccentricity Tilt Year Solar day 11.2 Earth 2.5 Earth 318 Earth 5.2 AU 0.048 3.1° 11.9 Earth years 9 hrs 56 mins Jupiter, King of the Planets An atmosphere unlike Earth’s 90% Hydrogen, 10% Helium, ~0.3% other stuff Very Rich similar to the Sun’s composition chemistry 0.3% contains methane, ammonia, other hydrocarbons, water, etc.. 500-600 mph winds are commonplace Incredible pressures Increasing temperatures with depth 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 The Great Red Spot A huge storm 25,000 km across Three Earths would fit inside Probably first observed over 300 years ago Cassini images Voyager 1 image 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 Jupiter’s Magnetosphere Liquid metal hydrogen generates a magnetic field 14x stronger than the Earth’s field Over 4 million km across J. Spencer A ring of ionized (electrically charged) particles surrounds Jupiter Stripped from Jupiter’s moon Io by Jupiter’s very powerful magnetic field Saturn Facts! Saturn has over 60 moons Equatorial radius Mass Eccentricity Year 9.45 Earth 95.2 Earth 0.056 29.5 Earth years Surface gravity 1.06 Earth Distance from Sun 9.55 AU Tilt 26.7° Sidereal day 10 hrs 33 mins 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 is contracts, heat is produced As on Jupiter, storms are produced between cloud bands No long-lasting storm like the Great Red Spot 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 Saturn’s Interior Similar structure to Jupiter’s 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 Jupiter’s Moons Jupiter has over 65 moons Most are small Some are captured asteroids The 4 largest are the Galilean moons Callisto, Ganymede, Europa, and Io Discovered by Galileo (early use of telescope) Io Europa Ganymede Callisto All Stirred Up The Galilean moons have weak magnetic fields Tidal and magnetic forces from Jupiter stirs 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 Io Innermost Galilean moon Most volcanically active body in the Solar System Volcanoes spew molten sulfur-loaded magma Constantly repaved surface - no impact craters Pillan Patera eruption Before & after Europa Icy crust 10 to 30 km thick Cracks and fissures on surface – upwelling? Evidence for a deep (~100 km) liquid water ocean beneath the crust Galileo Spacecraft Ganymede Largest moon in the Solar System Partly ancient surface, partly younger surface Younger surfaces about the age of the Moon’s maria Compared to our Moon: 50% larger 10% larger than Mercury! 100% more massive 40% less dense Interior more differentiated than Callisto, probably has an iron core 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 Saturn’s Famous Rings Two main rings (A and Several fainter rings (C B) 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 Titan Saturn’s largest moon bigger than Mercury second largest in Solar System Titan’s atmosphere Dense nitrogen/methane atmosphere (like smog) Only Solar System moon that has 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 Next Time The Edge of Town