the jovian planets and their moons - ursinus...
TRANSCRIPT
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The Jovian Planets and Their Moons
Jupiter
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Physical Properties of Earth and Jupiter
Jupiter Earth
E t i l R di 11 2 R 6378 kEquatorial Radius 11.2 REarth 6378 km
Mass 318 MEarth 5.976×1024 kg
Average Density 1.34 g/cm3 5.497 g/cm3
Surface Gravity 2.54 Earth gravities(at the base of the clouds)
9.8 m/s2
(at the base of the clouds)Escape Velocity 61 km/s 11.2 km/s
Surface Temperature -120 oC at the cloud tops -50oC to 50oC
Average Albedo 0.51 0.39 (mostly from clouds)
The length of a Jovian day is about 10 hours.
Falling
Rising
Belts – sinking, low pressure regions.Zones – rising, high pressure regions.
Why are belts dark and zones white?
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Jupiter’s Atmosphere
200
Clear hydrogen
-100 K Thickness of atmosphere is about 1000 km.
100
0
100
Alti
tude
(km
)
AmmoniaAmmonia
Ammonia Hydrosulfide
Water
150 K
200 K
270 K
No sharp boundary between gaseous atmosphere and liquid interior. Atmosphere gradually thickens and becomes liquid with transformation complete at a depth of about 1000 km.
-200
-100
-300
Water 270 K
600 K
Cloud colors due to ammonia hydrosulfide and photochemical reactions involving sulfur and phosphorus.
Motion of Zones and BeltsWind speeds ~ hundreds of km per hour.
Why such high wind speeds?
Why is the circulation in parallel bands?
Why does Jupiter emit
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Jupiter’s Great Red Spot – a cyclonic storm that has continued for more than 300 years.
Jovian Thunderstorms
Lightning flashes are as much as a thousand times as powerful as those on Earth.
What causes thunderstorms?
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Jupiter’s Aurora Oval
What causes aurorae?
Jupiter’s Magnetic Field
Jovian magnetic field is more than 10 times stronger than Earth’s magnetic field. Why?
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Internal Structure of Jupiter
Molecular Hydrogen
“Rocky” Core
Liquid Metallic Hydrogen
Jupiter’s Ring System
Jupiter’s rings are made of dark dust with a rocky composition. How do we know this?
Rings are not permanent butRings are not permanent but are replenished by dust knocked off satellites by micrometeorite impacts.
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Galilean Satellite Interior Models
Io Europa
GanymedeCallisto
r = 1820 kmρ = 3.55 g/cm3
r = 1565 kmρ = 3 g/cm3
2420 kr = 2640 kmρ = 1.9 g/cm3
r = 2420 kmρ = 1.79 g/cm3
Jupiter has more than 60 moons.Mercury: r = 2439 kmMoon: r = 1738 km
Io in Jupiter’s Shadow
Pillan Patera
Temperature pbetween 2600 and 3140oF.
Hottest terrestrial volcanoes have maximum temperatures of about 2240oF.
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Pele, Pillan Patera, and a New Volcano
Io is the geologically most active object in the solar system.
Pele
Pilan Patera A new eruption
Volcanic Plumes as high as 500 km.Eruptions powered by sulfur dioxide.
Source of Io’s Heat
• Heat of Formation? – No. Because of its small size, it cooled rapidly after it formed.
• Radioactive Decay? – No. A small object would have very little naturally radioactive material. The small amount of heat generated would be quickly lost.
• Tidal Heating. Yes. The continual flexing of a moon’s crust due to tidal interactions with the planet and/or other moons would effectively heat the moon, especially if its orbit is elliptical.
• PGanymed e = 2 PEuropa = 4 PIo.• Tides on Io as high as 100 m.`
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Io Flux Tube
Base of Io Flux Tube
Europa’s Surface
What does the smoothness of Europa’s crust tell us about its interior?
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Model of Europa’s Interior
Metallic CoreRelatively clean, icy crust
Liquid WaterRock
The Galileo probe measurements of the magnetic field induced in Europa by Jupiter’s rapidly rotating magnetic field demonstrate that under a brittle crust, there is a shell of salty water.
Ganymede
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Model of Ganymede’s Interior
Metallic Core
Icy Mantle
Icy Crust
Callisto
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Model of Callisto’s Interior
Crust – a Thin shell of mixture of ice and rock
liquid water
Mixture of ice and rockand rock
Saturn and its Moons
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Physical Properties of Jupiter and Saturn
Saturn Jupiter
E t i l R di 10 2 R 11 2 REquatorial Radius 10.2 REarth 11.2 REarth
Mass 95.2 MEarth 318 MEarth
Average Density 0.69 g/cm3 1.34 g/cm3
Gravity at the base of clouds
1.16 Earth gravities 2.54 Earth gravitiescloudsEscape Velocity 35.6 km/s 61 km/s
Surface Temperature -180oC at the cloud tops -120 oC at the cloud tops
Average Albedo 0.61 0.51
Saturn Compared with Jupiter
Cassini Division
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Jupiter SaturnJupiter
Comparison of the Atmospheres of Jupiter and Saturn
200 -200 K200
Clear hydrogen
-100 K
100
0
100
Alti
tude
(km
)
Clear Hydrogen
Methane Haze
100
0
100
Alti
tude
(km
)
AmmoniaAmmonia
Ammonia Hydrosulfide
Water
150 K
200 K
270 K
-200
-100
-300
Ammonia
Ammonia Hydrosulfide
Water
150 K
200 K
270 K
-200
-100
-300
Water 270 K
600 K
Oblateness
a ba−
ε =a
b
Rotation Axis
Planet OblatenessMercury 0
Venus 0
Earth 0 0034Earth 0.0034
Mars 0.009
Jupiter 0.0637
Saturn 0.102Note: In order for an object to move in a circle, it must experience a force toward the center of the circle. This force is called the “centripetal force”.
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What determines the internal temperature of a planet?
Primordial Internal Heator
Heat from Radioactive Decay
Sunlight
The planet’s albedo.
For Saturn, helium “rain” also heats up the interior. As the liquid helium droplets fall through the less dense liquid hydrogen, gravitational potential energy is converted into thermal energy.
Comparison of Internal Structures of Saturn and Jupiter
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Saturn and its Moons
Satellite Distance from Saturn (km)
Radius(km)
Mass(kg)
Mi 186 000 398 3 7 1019Mimas 186,000 398 3.7×1019
Enceladus 238,000 498 7.3×1019
Tethys 295,000 1060 6.2×1020
Dione 377,000 1120 1.0×1021
Titan 1,220,000 2575 1.3×1023
Iapetus 3,560,000 1440 1.6×1021
Titan’s Atmosphere
95% Nitrogen + CH4 + C2H6 + …
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Artist’s View of Huygens Descent to Titan’s Surface
Chunks of Ice on Titan’s Surface
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River Channels on Titan
Tethys
3 km deep crack
1060R km=
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Mimas
R = 196 km
Enceladus
Albedo = 0.9
R = 250 km
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Iapetus
R = 720 km
Dione
R = 560 km
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Problem 1: Calculate the period of revolution of Mimas around Saturn.
2 2 3GMP 4 a= π2 34 aP
GMπ
= M = 5.68×1026 kg a = 186,000 km
G = 6.67×10-11 Nm2/kg2G 6.67 10 Nm /kg
( )( )( )
2 5 3
211 26
2
4 1.86 10 10 mP
Nm6.67 10 5.68 10kg
−
π × ×=
⎛ ⎞× ×⎜ ⎟
⎝ ⎠
4P 8.2 10 s 0.95day= × =
Problem 2: Calculate Mimas’ average density.
MdensityV
= M = 3.7×1019kg 34V R3
= π ( )354 3.98 10 m3
= π ×
V =1.67×106 m319
16 3
3.7 10 kgdensity3.3 10 m
×=
×31100kg / m=
R = 398 km
False Color Image of Saturn’s Rings
C
CassiniDivision B
C
A
The radius of the inner edge of the Cassini division is 117,500 km. Particles at this distance have an orbital period of 0.476 day. How does this account for the existence of the Cassini division? What is the orbital period of Mimas?
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Shepherding Satellites
Saturn’s F ring
Shepherding Satellites
Coorbital Satellites(Janus and Epimetheus)
Dimensions of Janus: 110 km 80 km 100 kmDimensions of Epimetheus: 110 km 80 km 100 kmDimensions of Epimetheus: 110 km 80 km 100 km
Radius of Janus’ Orbit : 151,470 km
Radius of Epimetheus’ Orbit: 151,420 km
BF
A
A
FA on B
FB on A
A takes energy from B, and B gives energy to A.
B
B will eventually catch up to A, and the two moons will again exchange orbits.
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Uranus and Neptune
Physical Properties of Uranus and Neptune
Uranus Neptune
E t i l R di 3 98 R 3 81 REquatorial Radius 3.98 REarth 3.81 REarth
Mass 14.5 MEarth 17.1 MEarth
Average Density 1.29 g/cm3 1.66 g/cm3
Gravity at the base of clouds
0.919 Earth gravities 1.19 Earth gravitiescloudsEscape Velocity 22 km/s 25 km/s
Surface Temperature -220oC -216 oC at the cloud tops
Average Albedo 0.35 0.35
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Why is it blue?
Visual Image of Uranus Visual Image of UranusEnhanced to Show Bands
Internal Structure
hydrogen + helium
rocky slush
heavyelements
Diamonds in core?Source of excess thermal energy?
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Oberon
R = 775 kmLarge faultFlooded crater floors
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Titania
R = 805 km
No large craters
Umbriel
R = 585 km
Dark (albedo = 0.16)Heavily craterdAbsence of faults
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Ariel
R = 580 km
Lots of faultsBrightest surfaceSmoothed by floodingOrbital resonance withMiranda and Umbriel
Miranda
R = 242 km
Faults, ice-lava flowsRotated blocks of ice
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Uranus’ Rings
Thin layer of dark boulders.
Neptune
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Triton
Nitrogen frost.
Nearly circular orbit, but retrograde.Almost no craters.
Geysers and dark smudges.
Icy greenhouse effect.Tidal forces when captured (?) by Neptune?
Radius = 1360 km
Neptune’s Rings
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Nereid
Large, elongated orbit. Radius = 170 km
Twisted Ring in the Neptune Ring System