12a. Jupiter Jupiter & Saturn data Jupiter & Saturn seen from the Earth Jupiter & Saturn rotation & structure Jupiter & Saturn clouds Jupiter & Saturn atmospheric motions Jupiter & Saturn rocky cores Jupiter & Saturn magnetic fields Discovering Saturn’s rings Structure of Saturn’s rings Rings & shepherd satellites

Jupiter Data (Table 12-1)

Jupiter Data: Numbers Diameter: 142,800.km 11.19 . Earth Mass: 1.9 . 1027 kg 317.8 . Earth Density: 1.3 . water 0.24 . Earth Orbit: 7.8 . 108 km 5.20 AU Day: 9h.50m 30s 0.41 . Earth Year: 11.86 years 11.86 . Earth

Jupiter Data: Special Features Jupiter is the closest Jovian planet to the Sun Jupiter is the largest Jovian planet Jupiter is ~2.5 . mass of all other planets combined Jupiter has no solid surface Jupiter has a very colorful & dynamic atmosphere Great Red Spot, belts & zones… Jupiter’s interior probably consists of three layers… Atmosphere: Liquid molecular hydrogen Mantle: Liquid metallic hydrogen Core: “Metal” & “rock” Jupiter has 4 large & 12 small known moons Io is the most volcanically active body known

Jupiter As Seen From Earth The first telescopic observer of Jupiter Galileo Galilei 1610 Immediately noticed the four largest moons of Jupiter Recognized the similarity between them and the planets More recent telescopic observers Robert Hooke 1664 Noticed the Great Red Spot in Jupiter’s southern hemisphere It has persisted in some form until now Cassini 1690 Cloud bands drawn out by Jupiter’s very fast axial rotation Used these to determine 9h 50m 28s equatorial Jovian day Discovered Jupiter’s differential axial rotation Jupiter rotates fastest as its equator

Jupiter is Made of Low-Mass Gases Jupiter is mostly hydrogen & helium The numbers By mass ~ 71% H2 ~ 24% He ~ 5% others By atoms ~ 91% H2 ~ 8% He ~ 1% others The evidence Easily obtained spectra of CH4 (methane) & NH3 (ammonia) Cold H2 & He are extremely difficult to detect UV spectra in 1960 Jupiter does have a rocky & metallic core This may have been the “seed” for the rest of Jupiter

Spacecraft Images Show Cloud Details Pioneer 10 & Pioneer 11 fly-bys 1973 & 1974 First close-up images of Jupiter Spectacular images of Galilean moons, esp. volcanic Io Voyager 1 & Voyager 2 fly-bys 1979 Spectacular close-up images of Jovian storm systems Additional details of most Jovian moons Galileo atmospheric probe & orbiter 1995 Descended through a clear area in Jupiter’s clouds Severely crippled yet still in operation in October 2002 Cassini 2000 The primary mission is to Saturn Imaged Jupiter during its gravity-assist [slingshot] fly-by Simultaneous observations by Galileo

Patterns In Jupiter’s Clouds

Jupiter Seen From Far & Near Earth-based telescope Voyager 1 spacecraft

Five Historic Views of Jupiter

Jupiter’s Great Red Spot Solar System champ Longest lasting storm system Since 1664 Largest storm system ~ 25,000 mi Basic characteristics Imbedded in Jupiter’s southern hemisphere Much higher than surrounding clouds Circulates counterclockwise Characteristic of a high pressure system Similar to high pressure systems in Earth’s atmosphere Size varies considerably From ~ 1 to ~3 times Earth’s diameter Color varies considerably From deep red to light pink

Voyager 2 & Jupiter’s Great Red Spot

Jupiter & Ganymede: A Family Portrait

Three Factors Affect Cloud Motions Insolation Incoming solar radiation Jupiter’s orbit is ~ 5.2 AU from the Sun ~ 3.7% as much energy per m2 as Earth Jupiter’s albedo is 0.44 compared to Earth’s 0.39 Effectively reduces solar energy to ~ 3.3% of Earth Sunlight is absorbed directly by Jupiter’s atmosphere Jupiter’s internal heat Jupiter emits ~ 2x as much energy as it gets from sunlight Residual heat from Jupiter’s formation New heat from He condensation Heat of condensation Differential axial rotation Multiple convection cells in Jupiter’s atmosphere Drawn out into bands parallel to Jupiter’s equator Adjacent bands move in opposite directions Zonal winds

Spectroscopy of Jupiter’s Atmosphere Three primary cloud layers Upper layer ~ 20 km below Tmin Ammonia (NH3) ice crystals Middle layer ~ 40 km below Tmin Ammonium hydrosulfide (NH4SH) ice crystals Lower layer ~ 60 km below Tmin Water (H2O) ice crystals Major cloud features Belts & zones Belts are bands of descending air Relatively low & warm Zones are bands of ascending air Relatively high & cool Brown & white ovals White ovals lie relatively high in Jupiter’s atmosphere Smaller versions of the Great Red Spot Brown ovals lie relatively low in Jupiter’s atmosphere

Jupiter’s Upper Atmospheric Structure

Jupiter’s (Low) Belts & (High) Zones

Jupiter’s Cloud Colors Distinctive “Earth tones” Yellow, brown, pink, red… These vary over time & space Source of colors All three cloud layers are white if pure Spectroscopy reveals no substantial impurities Jupiter’s moon Io is extremely active volcanically Io has abundant sulfur compounds Io has the same colors as Jupiter’s clouds Io spews matter into space near Jupiter Jupiter’s cloud colors may come from Io’s eruptions

Jupiter’s Deep Atmosphere: S-L 9 Comet Shoemaker-Levy 9 16-22 July 1994 23 visible fragments entered Jupiter’s atmosphere All less than ~ 1 km in diameter Entry speed of ~ 60 km . sec–1 ~ 130,000 mph Satellites orbit Earth at ~ 8 km . sec–1 Largest fragment energy equivalent of 6 . 108 megatons 10,000°C fireballs rose 3,000 km above the clouds Hopes for eruptions of deep atmospheric layers Confounded by uncertainties about comet’s composition

S-L9: The String of Pearls Comet

Comet Shoemaker-Levy 9 Hits Jupiter

Jupiter’s Deep Atmosphere: Galileo Galileo atmospheric probe 7 December 1995 Only spacecraft to ever enter Jupiter’s atmosphere Entry speed of ~ 49 km . sec–1 ~ 106,000 mph Decelerated to ~ 40 km . hr–1 in 3 minutes ~ 25 mph Descended by parachute for ~ 1 hour Reached a depth of ~ 200 km & 24 x Earth’s air pressure Important findings Relatively rare but extremely powerful lightning Nearly constant winds of ~ 650 km . hr–1 Much faster than solar-driven high altitude winds This wind energy must come from Jupiter’s interior Cloud layer measurements The Galileo Probe had bad luck & entered a clear warm spot Traces of NH3 & NH4SH clouds but no sign of H2O clouds Atmospheric gases Virtually identical to the Sun Only one-half the expected amount of atmospheric H2O vapor

The Galileo Probe Timeline

Oblate Shape Reveals a Rocky Core Even small telescopes reveal Jupiter’s oblate shape Distinctly larger equatorial than polar diameter ~ 6.5 % difference for Jupiter ~ 0.34% difference for Earth Axial rotation spins equatorial material away Centrifugal effect Planetary core mass modifies the centrifugal effect Metallic & rocky inner core Estimated to be ~ 2.6% of Jupiter’s mass Only ~ 8 x Earth’s mass yet ~ 86% Earth’s diameter Liquid “ices” outer core Primarily water (H2O), methane (CH4) & ammonia (NH3) Estimated to be ~ 3,000 km thick

Jupiter’s Four-Layer Internal Structure

Metallic Hydrogen & Magnetosphere Radio observations of Jupiter 1950’s Evidence of electric currents Different types of radio emissions Thermal emissions Blackbody radiation Non-thermal emissions Wavelengths of a few meters Decametric radiation Powerful electric currents in Jupiter’s ionosphere Wavelengths of a few tenths of a meter Decimetric radiation Extremely fast electrons in a very strong magnetic field Jupiter’s magnetic field is ~ 14 x Earth’s magnetic field Possible causes Hydrogen is a liquid metal above 1.4 . 106 atmospheres This pressure is reached ~ 7,000 km below Jupiter’s clouds The “gas giant” Jupiter is mostly liquid metallic hydrogen

Jupiter’s Magnetosphere is Immense Spacecraft measurements Pioneer & Voyager Magnetosphere is ~ 3.0 . 107 km in diameter seen from the Sun ~ 210 times Jupiter’s diameter as seen from Earth ~ 2.5 times the Moon’s diameter as seen from Earth ~ 6.3 times the Moon’s area as seen from Earth Magnetosphere extends beyond the orbit of Saturn Jupiter’s magnetotail is ~ 6 AU long Emissions variations repeat every 9h 55m 28s Taken to be the core axial rotation rate of Jupiter Galileo Suffered extensive radiation damage in orbit around Jupiter Basic characteristics Jupiter’s magnetosphere is filled with plasma Solar wind gusts rapidly deflate Jupiter’s magnetosphere Size varies by a factor of 2

Jupiter’s Magnetosphere A schematic view A radio view

Important Concepts: Jupiter Jupiter data ~ 11.2 times Earth’s diameter ~ 318 times Earth’s mass ~ 2.5 times the mass of all planets Jupiter as seen from Earth Distinctly oblate shape Distinctive cloud bands & storms Four extremely obvious moons Distinctive features Axial rotation period of ~ 10 hours Solar System’s most colorful clouds Composed mostly of H & He Almost same composition as the Sun Jupiter’s cloud details Prominent cloud belts & zones Prominent spots Great Red Spot White & brown ovals Jupiter’s deeper atmosphere Comet Shoemaker-Levy 9 23 fragments < 1 km in diameter Galileo Probe spacecraft 1 tiny spacecraft for ~ 1 hour Jupiter’s four-layer internal structure Ordinary gaseous hydrogen & helium Helium & liquid metallic hydrogen Liquid “ices” (H2O, CH4 & NH3) Rocky & metallic core Jupiter’s magnetosphere Magnetic field strength ~ 14 x Earth’s Circulating liquid metallic hydrogen Very fast axial rotation Magnetic field size Width of ~ 210 x Jupiter’s diameter Length of ~ 6 AU (past Saturn’s orbit) Deflates quickly due to solar wind