the outer planets
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The Outer Planets
Cosmic Abundance of ElementsHydrogen H 1 1,000,000
Helium He 2 80,000
Carbon C 6 363
Nitrogen N 7 112
Oxygen O 8 851
Neon Ne 10 117
Sodium Na 11 2
Magnesium Mg 12 32
Aluminum Al 13 3
Silicon Si 14 45
Sulfur S 16 16
Argon Ar 18 1
Calcium Ca 20 2
Iron Fe 26 36
Nickel Ni 28 2
Major Constituents
Gas Formula Jupiter Saturn
Hydrogen H2 86% 92%
Helium He 14% 7%
Methane CH4 0.2% 0.2%
Ammonia NH3 0.02% 0.02%
Water H2O ~0.2% (?) ~0.4% (?)
Interiors: Big H2 Atmospheres
Jupiter vs Saturn
Jupiter’s Ammonia Clouds:
Belts: Dark bands
Zones: Bright bands
Great Red Spot
White Ovals
The GRS has lived at least 300 yrs. Ovals have been seen to survive tens of years
Jupiter’s clouds result from convection.
1) Hot air expands.
2) Lighter than the rest of the air, it rises.
3) As it rises, it cools and condenses forming clouds.
4) When it is cooler than the ambient air, it sinks.
Great Red Spot
Saturn’s Clouds
Uranus
Absorption of sunlight at red wavelengths by methane renders the planet blue.
Neptune
Neptune emits more energy from its interior than does Uranus. This energy drives weather. The colder temperatures cause methane to condense in the upper atmosphere – these are the clouds that we see.
Jupiter’s RingsSilicate dust, 10,000 times more transparent than window glass.
Moons
A typical, heavily cratered, terrain.
Saturn’s moon, Tethys
Their densities tell us that they are 1/2 rock & 1/2 ice.
Jupiter’s Moons
Europa
Few craters
A terrain containing elements that were recently dislodged can be seen to neatly fit together if rotated and translated in position.
Io
• Images\iovol_vgr.gif
Io
What fuels Io?
Each time Ganymede orbits once, Europa orbits twice, and Io orbits 4 times.
Plumes fountain 500 km above the Surface
Io’s surface is almost devoid of craters, for it is being repaved at a rapid rate.
The glow of warm lava.
A pool of lava (black) covered with sulfur deposits (orange). This is called Tupan Patera after the Brazilian thunder god.
Images taken from the Galileo spacecraft.
Io is hot
Lava flows on Io exceed 1500 K in temperature. Lavas this hot are not sulfur (which would evaporate immediately). This is hotter than present lavas on Earth (1300-1450 K). Instead these lavas are likely ultramafic (rich in Mg and Fe), similar to the lavas that occurred on early Earth.
Present hypothesis, a ~100 km thick crust floats on top of a worldwide ocean of magma 800 km deep.
Triton Neptune’s Largest Moon:
Triton
On Triton the main component of the atmosphere, nitrogen, exits in vapor pressure equilibrium.
That is, it exists as an ice on the surface and as vapor in the atmosphere, in the same way that water exists as liquid and ice on Earth’s surface and as a gas in the atmosphere.
The amount of gas depends on the temperature. Less exists at cooler temperatures.
This is seen on Earth with the condensation of water at dew point.
Atmosphere:
1.6x10-7 bar 38K Nitrogen
Summary
• Giant planets are large gas planets with nearly solar elemental abundances.
• They have small ice-rock cores. • Their moons are ½ rock and ½ ice. • Most moons display heavily cratered terrains. Io, Europa,
Triton and Titan are exceptions. • All jovian planets sport rings of differing thicknesses,
compositions & character. • Titan supports an atmosphere second only to Venus’
(considering bodies with proper surfaces). It is rich with organics, and its origin is unknown.
• The Cassini mission to the saturnian system is in route and functioning well.
Titan: a moon with an atmosphere
Saturn’s largest moon compared to Jupiter’s largest moons
GanymedeSize: 4800Mass: 1.5x1023
CallistoSize: 5268Mass: 1.1x1023
TitanSize:5150 kmMass: 1.3x1023
Observações da alta atmosferaObservações da alta atmosfera
Composition of Titan’s Composition of Titan’s stratospherestratosphere
MoleculeMolecule Abundance Abundance
NN22 65-98% 65-98%CHCH44 2-10% 2-10%HH22 0.2-0.6% 0.2-0.6%COCO 6-150 ppm 6-150 ppmCHCH33DD 5-180 ppm 5-180 ppmCC22HH66 13-20 ppm 13-20 ppmCC22HH22 2-5 ppm 2-5 ppmCC33HH88 0.5-4 ppm 0.5-4 ppmCC22HH44 0.09-3 ppm 0.09-3 ppmHCNHCN 0.2-2 ppm 0.2-2 ppmHCHC33NN 80-250 ppb 80-250 ppbCHCH33CC22HH 4-60 ppb 4-60 ppbCC44HH22 1-40 ppb 1-40 ppbCC22NN22 5-16 ppb 5-16 ppbCOCO22 1.5-14 ppb 1.5-14 ppb
Derived from radiative transfer analyses of Voyager, ISO and ground-based data.
Oceans?Oceans?CH4
C2H6
C2H2
haze
+ CH4 -> other hydrocarbons
Methane in atmosphere is depleted in107 years.
Either methane is supplied or we are witnessing Titan at a particular moment in its history.
Oceans containing methane explain the near saturated tropospheric conditions,provide a source for methane, and don’t requirea penchant for being lucky.
Flasar et al. Science 221, 55Lunine et al. Science 222, 1229
Ocean (CH4, C2H6, N2)
hν
Production RateProduction Rate
SpeciesSpecies FluxFlux Depth*Depth* PhasePhase
CC22HH66 5.8x105.8x1099 cm cm-2-2 s s-1-1 600 m600 m liquidliquid
CC22HH22 1.2x101.2x1099 cm cm-2-2 s s-1-1 100 m100 m solidsolid
CC33HH88 1.4x101.4x1088 cm cm-2-2 s s-1-1 20 m20 m liquidliquid
HCNHCN 2.0x102.0x1088 cm cm-2-2 s s-1-1 20 m20 m solidsolid
HazeHaze 1.5x101.5x10-14-14 g cm g cm-2-2 ss-1-1 60 m60 m solidsolid
Taken from Lunine et al. 1989. Based on Yung et al. 1984, Raulin (1984)
* Depth assuming global coverage & 4.5 Gyr of production
Expected Surface ScenarioExpected Surface ScenarioSagan & Dermott 1982Sagan & Dermott 1982
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Titan’s Surface
HST images
Peter Smith et al.
U. of Arizona
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Testing Cassini(Jet Propulsion Laboratory, California)
We can see the main antenna.
All the instruments (e.g. the cameras) are covered.
Huygens Probe,European SpaceAgency
We can see the shield that protects the instruments against the heatof entry into theatmosphere.
In 2005, the desent of Huygen’s into Titan’s atmosphere.
At 170 km altitude, Huygens releases the shield and beginsmeasurements.
Cassini-Huygens spacecraft, on a Titan IV rocket, waiting for takeoff.
15 October 1997
A perfect takeoff that saved fuel.
ISS Images
Huygens DIRS Descent Huygens DIRS Descent MovieMovie
View of Landing Site
Ice Mountains
Landing Site
Huygen’s Huygen’s DISR ImagesDISR Images
PI: Marty TomaskoPI: Marty TomaskoUniversity of University of
ArizonaArizona
Foreground stones are 6 inches
DISR
More DISRImages.
Washes flow Washes flow downhilldownhill
Tomasko et al. Nature 438, 765
Huygens aterrizou ~30km Huygens aterrizou ~30km
ao sul das dunasao sul das dunas
Imagem do Cassini Radar (no modulo orbital)
Sitio de aterrissagem
Larry Soderblom
Tropical DunesTropical Dunes
Washes in XanaduWashes in Xanadu
Cassini RADAR
Lakes
Seas
TitanTitan
60o N latitude line
~ 1 m of surface CH~ 1 m of surface CH44
~ 4 m of atmospheric CH~ 4 m of atmospheric CH44
Cassini Radar
2.7 km of water on the surface 2.5 cm of atmospheric water EarthEarth
Sotin et al. N
ature 435, 786 (2005)
CryovolcanismCryovolcanism
A Mystery about TitanA Mystery about TitanWhere is the ethane Where is the ethane
(C(C22HH66)?)?
N2, CH4
Atmosphere
C2H6
A Mystery about TitanA Mystery about TitanWhere is the ethane Where is the ethane
(C(C22HH66)?)?
N2, CH4
Atmosphere
C2H6
Titan’s Two Kinds of Clouds
40
20
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Ethane(C2H6)
Methane(CH4)
SummarySummary
Titan, Saturn’s largest moon, has an atmosphere10 times thicker than Earth’s.
This atmosphere is mainly of N2 and contains a lot of organic material.
Titan sports a methane cycle, with clouds, rain & seas.
Methane is the source of organic material in Titan’s atmosphere and on its surface.
It’s not entirely clear how and when Titan outgassed its methane, but the dearth of ethane suggests that it happened within 1 billion years.
The complexity of the organic chemistry is unclear.
Um Balão para Titã
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