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JUPITER GLG-190 - The Planets Chapter 9 LECTURE OUTLINE Introduction Atmosphere composition Weather Zones and Belts Storms Cloud Layers Internal structure Magnetic field Sign spotted in Edinburgh UK GAS GIANT (JOVIAN) PLANETS Orbit outside of asteroid belt Accreted in colder parts of solar nebula beyond “snow line” Mostly hydrogen and helium Thick cloudy atmospheres snow line TERRESTRIAL VS. JOVIAN PLANETS Compositional differences from inner planets shown by densities Jupiter: 1.33 g/cm3 (about same as Sun) Saturn: 0.7 g/cm3 (less than water) Uranus 1.30 g/cm3 Neptune: 1.76 g/cm3 Values for inner planets and Moon range from 3.3 to 5.5 g/cm3 Low densities indicate materials less dense than rock and metal gas, liquid, and ice BASIC JUPITER DATA Orbital radius of 5.2 AU Largest planet Diameter = 11 x Dearth Mass = 318 x Mearth (2.5x mass of all other planets combined) Low density: 1.33 g/cm3 (about same as Sun) Short day: 9h 55m Axial tilt 3.1° Strong magnetic field 63 confirmed satellites Four major moons: Io, Europa, Ganymede, Callisto Faint rings JUPITER: ALMOST A STAR? Jupiter is almost as large as a planet can be… At 13 MJupiter deuterium fusion into helium occurs in the core brown dwarf At 70-80 MJupiter hydrogen fusion into helium occurs in core low-mass star Gliese 229 A and B COMPOSITION OF UPPER ATMOSPHERE Spectroscopic results combined with Galileo atmospheric probe (right) measurements Mostly H + He (99%) Most measured elements are enriched relative to H (compared with Sun) Lower solar ratios of Xsun/Hsun loss of H during formation of Jupiter ATMOSPHERIC STRUCTURE Top of troposphere (0.1 bar) assigned altitude of “0 km” (right) Higher temperatures at low altitudes due to internal heat Altitudes and types of clouds differ… Ammonia (NH3) clouds highest/coldest Ammonium hydrosulfide (NH4SH) clouds intermediate levels (color from breakdown to form sulfur compounds?) Water ice clouds lowest/warmest ROTATION & SHAPE Jupiter is not solid atmosphere rotates faster at equator Rapid rotation and gas/liquid structure yield equatorial bulge 143,884 km (equatorial) vs. 133,709 km (polar) True rotation shown by measurements of rotation of magnetic field 9 hr and 55 m 29.7 s WEATHER OF JUPITER Alternating counter-flowing light zones and dark belts Rapid rotation rate wraps convention cells around planet Different colors see different depths into atmosphere Great Red Spot is top of large cyclone Equatorial zones and belts rotate faster than those at higher latitudes and at poles ZONES AND BELTS ON JUPITER Zones and belts are zonal jet streams Light colored zones Wind direction alternates between adjacent zones and belts Two always found next to each other Upward moving convective currents Cooling produces white clouds of ammonia/water ice Ice rains out Darker belts Downward sinking “dry” gases Lack of clouds allows view of lower, darker layers CLOUD BANDS JUPITER'S ATMOSPHERIC CIRCULATION Equatorial jet Rotation 9 hr 50 m Eastward winds 360 km/h High latitude winds Rotation 9 h 55 m (close to true rotation) East and westward winds 100 km/h max Polar vortex DETAILED STRUCTURES Boundaries of zones and belts have complex turbulence and vortex phenomenon Dominated by physics known as fluid mechanics Dense cold atmosphere behaves as fluid rather than gas Fluid mechanics predict two types of patterns Viscous flow: fluid slips past a second fluid of different density wave-like features form at boundary of two fluids Turbulent flow: stream of fluid breaks up into individual elements, called eddies (eddies can develop into cyclones) CYCLONES Energy to power turbulence in Jupiter's atmosphere comes from internal heat Cyclones develop due to very large Coriolis effect Gases at lower latitudes travel faster than at higher latitudes spin Cyclones are regions of local high or low pressure Direction of spin differs in two hemispheres Brown ovals are low pressure cyclones/storms in North White ovals are high pressure cyclones/storms in South Details of the circulation patterns of individual bands Merging of two storms in a band GREAT RED SPOT Large southern hurricane 18,000 x 12,000 km (2x size of Earth) At least 300 years old (persists because of large size?) Associated clouds are 8 km above neighboring cloud tops IMPACTS ON JUPITER Comet Shoemaker-Levy 9 Torn apart by Jupiter’s gravity Fragments penetrated below ammonia clouds before exploding form holes into lower hotter part of atmosphere Produced dark S- and C-rich clouds that dissipated after few months IR image showing 2 impact sites (lower left) Fragments of Shoemaker-Levy 9 JULY 20, 2009 IMPACT Anniversary of Apollo 11 landing on Moon Completely unexpected we lack of knowledge of distribution of small bodies in Solar System INTERNAL STRUCTURE No samples available theoretical models of interior Need to determine behavior of hydrogen and helium at high pressures and temperatures Correct for effects of pressure (conditions at Jupiter’s center: 25000 K and 100 Mbar) INTERNAL STRUCTURE Pressures high enough to form liquid metallic hydrogen (H) Electrons not bound to atoms in metallic structure move freely Convection currents in liquid metallic hydrogen produce strong magnetic fields Uppermost layer dominated by molecular hydrogen (H2) Other elements in small abundances HELIUM RAIN Dissolved He becomes immiscible in upper part of metallic hydrogen layer (region labeled Helium rainout) Forms liquid He droplets in He droplets sink deeper into interior Produces He depletion of upper atmosphere Neon dissolves in He droplets also sinks into interior Accounts for depletion of Ne seen in upper atmosphere CORE Rocky core needed to account for details of gravity field (otherwise no evidence for core) Core is probably 14-18x Mearth Data from Juno probe (launched Aug. 2011; arrive July 2016) will better constrain core size Inner part of core composed of silicate minerals, oxides, metals Inner part of core surrounded by layer of ices (methane, water, ammonia) All materials would have unknown structures at such extreme high pressures INTERNAL HEAT Infrared radiation (IR) measurements done by Voyager spacecraft and Hubble telescope Jupiter gives off 1.67x more heat than it gets from Sun Heat sources differ... Jupiter retains heat from contraction from protosolar nebula (may still be contracting) Potential energy released by helium rain also probably contributes heat, but to a much lesser extent JUPITER’S MAGNETOSPHERE Magnetic field 19,000x stronger than Earth’s Produced by electrical currents flowing inside metallic hydrogen interior Inclined 10 relative to rotational axis N and S poles swapped compared with Earth Huge magnetosphere Magnetotail extends out to orbit of Saturn Large sea of trapped, charged particles like Earth’s Van Allen Belts Vastly larger and more energetic aurorae than on Earth Sun (yellow) shown with Earth’s magnetosphere inside (to scale) RADIO EMISSIONS FROM JUPITER Two sources of radio emissions Thermal radiation Shorter wavelength radio waves produced by internal heat (cyan) Distribution of wavelengths followed Planck’s law Nonthermal radiation Longer wavelength radio waves produced by electrons spiraling in magnetic field synchrotron radiation SYNCHROTRON RADIATION Synchrotron radiation created when fast charged particle interacts with magnetic field Magnetic field causes particles to change direction by exerting force on them perpendicular to their movement direction Particles are accelerated along spiraling curved path and radiate radio waves AURORA Strong magnetic field captures charged particles from solar wind and ions ejected from Io Particles trapped in inner magnetic belts and reflected back and forth between north and south magnetic poles of Jupiter Auroras produced from this interaction Location of Io’s flux tube