Download Jovians: General Characteristics

Jovians: General Characteristics
• Jovians are BIG - (99.5% total mass!)
• Jovians have Thick Atmospheres
• Jovians do NOT have Solid Surfaces
• Jovians have small rock/ice inner core
• Jovians have Rings
• Jovians have LOTS of Satellites
• Jovians rotate FAST (10-17 hours!)
Jovian Planets: Masses & Sizes
Planet
Mass
(kg)
Jupiter
Mass
(Earth
masses)
Radius
(km)
Radius
(Earth Radii)
1.898 x 1027 317.7
71,492
11.2
Saturn
5.69 x 1026
95.2
60,268
9.4
Uranus
8.682 x 1025 14.5
25,559
4.0
Neptune
1.024 x 1026 17.1
24,764
3.9
Structure of Gas Giants
(Atmospheric) Composition
Jupiter (and Saturn) are quite like the Sun:
(but very different from Earth)
Percent
by mass
Sun
Jupiter
Atmosphere
Saturn
Earth
Atmosphere Atmosphere
Hydrogen
74%
75%
92%
<1%
Helium
25%
24%
6%
5%
“Metals”
1%
1%
2%
94%
Density of Jovians ~1-2 g/cc (Earth ~ 5.5)
5
Jupiter & Saturn GLOW
Jupiter emits 2x as much energy as it receives
from the Sun!!
WHY??
Emission from Jupiter & Saturn
Conversion of Gravitational Potential Energy into Heat...
Just like PROTOSTARS!!
How did Jovians form??
Jupiter
Mass ~ 318 Earth Masses
Size - 11.2 Earth Radii (71,492 km)
Density - 1.33 g/cc
Jupiter is OBLATE
Orbital Period - 11.7 years
Orbital Distance - 5.2 AU
Rotation Period - 9.9 hours
“Surface” T (1 bar) - 165 K
Core T - >36,000 K
Obliquity - 3.1∘
New Horizons flyby
Jupiter - Bodacious B (Magnetic Field)
20,000x
stronger than
Earth!
passes through
Saturn’s orbit
Why so Strong?
What is Metallic H (& He)?
Molecular H & He
Metallic H & He
images fr. Burkhard Militzer
High pressure “squishes” molecules:
electrons decouple; nuclei become degenerate
10
Spinning metallic hydrogen insides
create strong magnetospheres
• Aurorae!
11
Spinning metallic hydrogen insides
create strong magnetospheres
• Aurorae!
Jupiter’s Atmosphere
Percent
by mass
Jupiter
Atmosphere
Hydrogen
75%
Helium
24%
“Metals”
1%
Layered Structure Includes Methane, Ammonia & deep layer of
water or ice droplets.
Weather on Jupiter
Belts and Zones
differential Rotation
Images from Cassini
(Fast) Differential Rotation!!
300-500 km/hr
Causes a lot of WEATHER!
Jupiter - Great Red Spot
Giant Cyclone
More than one! discovered 1664
rotates in 6 days
BIGGER than
Earth!
HST 2006
15
Why is the Red Spot Red?
• The Red Spot is actually quite stuck up,
(about 8km).
Galileo Spacecraft,
1996
IR Data
Blue: Lower (warmer)
Yellow: Higher (cooler)
16
Cassini
Looking inside CONTINENT-SIZED storms....
HST infrared images. March, 2007.
Cloud colors
correspond to
different T
Jupiter - Rings
Galileo image
A
(Many) Moons of Jupiter
59
X at last count (most recent 2004)
63
55
X outer satellites:
59
- irregular shapes
- small (1-184 km)
- orbits months-years
- retrograde/eccentric/inclined orbits
Likely captured asteroids (like Phobos & Deimos)
image from Wikipedia
A
4 Galilean Satellites
Orbital Motion of the Galilean Satellites
Io: 1.8 days
Europa: 3.6 days
Ganymede: 7.2 days
Callisto: 16.7 days
• Motion is Observable!
• Io, Europa, and Ganymede in a 1:2:4 resonance
Other Worlds??
Animation: A.
Cidadao
Callisto - Outermost Galilean Satellite
Density = 1.8 g/cc
Orbital Period = 16.7 days**
Mass = 1.47 Mmoon
**Not in a resonance - why?
•Icy crust
•Lots of large impact craters
•Dark mineral surface deposits
•No Signs of Geologic Activity •internal T?
image from Galileo
Callisto - Outermost Galilean Satellite
No evidence for Geologic activity
• Mixed Ice/Rock
• Antifreeze Ocean?
• Icy Crust
COLD
Ganymede - Largest Satellite in SS
Density = 1.9 g/cc
Orbital Period = 7.2 days
Mass = 2.02 Mmoon
Ages?
Dark vs. light
surfaces
Cryovolcanoes!
images from Galileo
Europa - 2nd closest Galilean Satellite
Density = 3.0 g/cc
Orbital Period = 3.6 days
Mass = 0.65 Mmoon
Smoothest Moon
Stripes and Cracks
Few Impact Craters
?
images from Galileo
Europa - An Underground Ocean?
• Smooth Surface -> Young (Geologically Active)
• Frost and WATER ICE
• Possible Ocean of liquid water underneath?
• Life?
images from Galileo
Io - Innermost Galilean Satellite
Density = 3529 kg/m3
Orbital Period = 1.8 days
Mass = 1.22 Mmoon
Yellow
No Craters
Surface YOUNG
Io Volcanically Active!!
True color image from Galileo
WHY??
Io - one stressed out moon!
TIDAL FORCES
J/E/G all pulling on IO
• Io squeezes and flexes
• Energy added at a rate of 1
trillion 100-watt light bulbs per
second
TeIO HEATS UPxt
Io - Most Active World in the Solar System
Voyager I
• 8 active volcanoes
• detected sulfur/sulfur dioxide
Galileo
• Plumes 70-280 km (Boston
anyone?)
• Recent sulfur deposits
• Hotspots
New Horizons
Composition of Galilean Satellites
Average Densities:
Io 3.5 g/cc
Europa 3.0 g/cc
Ganymede - 1.9 g/cc
Callisto 1.8 g/cc
WHY?
Rocks - ~3.0 g/cc
Ices - 1-2 g/cc
Jupiter is a mini-Solar System!!