Download The Jovian Planets Sizes of Jovian planets compared to the Earth

The Jovian Planets
Jupiter
Saturn
Outline
Uranus Neptune
• Low Density
• Small “Core”/Atmosphere Ratio
• Rings
• Many Natural Satellites
Spacecraft Missions to the Jovian Planets
Four Major Missions
• Pioneers 10 & 11 (launched 1972)
• Voyagers 1 & 2 (launched 1977)
• Galileo (launched 1989)
• Cassini-Huygens (launched 1997)
Difficulties/Issues with sending probes to Jovian planets
• Energy source: solar panels + internal radioactive generators
needed
• Distance from Earth: autonomous
• Destruction of spacecraft by debris: asteroids, rocks, etc.
• Trajectory: gravity assisted
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Spacecraft Missions to Jovian Planets
General Properties of Jovian Planets
Properties of Jupiter & Saturn
Equatorial bulges
Internal heat sources
Galileo Probe & Jovian atmospheric structure
Belts & Zones
The Great Red Spot
Rings
Voyagers
Sizes of Jovian planets compared to
the Earth
Properties of Jupiter
• Composition: 75% hydrogen,
24% helium + methane,
ammonia, water ice…
• Average Distance from the
Sun: 0.7 light hours = 5.2 AU
• Rotation Rate
9h55m30s – Magnetic Field
9h50m30s – Equatorial Clouds
9h55m41s – High Latitude Clouds
Note: Hydrogen and Helium
• Orbital Period: 11.9 Earth
are colorless.
years
• Axis Tilt: 3.1°
• Number of Moons: ~ 61
The Jovian planets have equatorial
bulges
• Rotation Rates ~ 10-17 hours
• Gravity makes planets spherical
• Rotation makes planets bulge at the equator
(Note: This keeps rings/satellites aligned with equator)
Properties of Saturn
• Average Distance from the
Sun: 1.3 light hours = 9.5 AU
• Rotation Rate
10h39m24s – Magnetic Field
10h14m – Equatorial Clouds
10h40m – High Latitude Clouds
• Orbital Period: 29.5 Earth
years
• Axis Tilt: 27° (i.e., Seasons:
Note: tan “smog” that overlies
UV + Methane → Ethane in
clouds below gives Saturn its
the Summer
color.
• Number of Moons: ~ 31
• Equator is 10% wider than
pole-to-pole
Jupiter & Saturn are about as large
as planets can be
Internal Heat Sources
Jupiter & Saturn radiate twice as much heat as they receive from
the Sun
• Earth radiates 0.005% as much energy as it receives from the
Sun
Source of heat from Jupiter is the slow contraction of the planet
• Gravitational potential energy → kinetic energy → thermal
energy
Jupiter
A brown dwarf is an object greater than about 13 Jupiter masses, but less
than 80. So it is bigger than Jupiter, but smaller than a star. It does not fuse
hydrogen, but it can fuse deuterium (proton+neutron nucleus).
Source of heat from Saturn is Helium rain
• At lower temperature & pressure of Saturn, liquid helium does
not dissolve with liquid hydrogen
• Deficit of Helium relative to Hydrogen has been measured in
the outer atmosphere of Saturn
1995: Galileo probe dropped into
Jupiter’s atmosphere
Probing Jupiter’s Atmosphere – The Galileo Probe (video)
(UV)
Troposphere:
turbulent clouds due
to the Greenhouse
effect
Jovian
Atmosphere
Comparison
cold enough for water to
condense, etc…
Internal structure of Jupiter
• Note: The behavior of
Hydrogen & Helium at high
temperatures & pressures is
not well understood
Belts & Zones
• Strong Coriolis forces divide
circulation cells into bands
• Convection results in bands
of different color
- Zones: rising, cooling air out
of which ammonia
condenses into clouds
- Belts: falling air depleted in
clouds; allows clouds below
to be seen
The Great Red Spot
• Storm that has persisted for at least 300 years
• Size: twice as wide as the Earth
• Why are such storms so long-lived?
→ No solid surface to sap away energy (as happens on the
Earth)
Rings
• Composition: mixture of
rocks of varying sizes
comprised mostly of water
ice (high albedo)
• Dimensions of Saturn’s rings:
270,000 km x 10s of meters
• Roche zone: tidal forces ~
binding gravitational forces
• Note: smaller rocks are held
together by gravitational &
electrostatic forces, & thus
can survive
Jupiter’s Rings
• Jupiter’s rings are less
prominent than Saturn’s
• Why? Smaller particles
Features in Rings
• Gaps are present in the
rings. They are created by
Gap Moons that nudge
particles out of particular
orbits
• Spokes: particles levitated
out of ring plane by forces
associated with the
magnetic fields
Origin of Rings
• Roche zone: within 2 to 3
planetary radii of any
planet, the tidal forces on
an object are comparable
to the force of gravity
holding it together
• Tidal forces could, in
principle, rip a moon
apart, or keep a moon
from forming
Origin of Rings
• Theory 1: a large moon strayed too close to its planet as a
result of an impact.
Problem: such an unlikely event would have to have happened
to all of the Jovian planets
• Theory 2: they formed from leftover chunks of rocks and
ice that condensed into a disk of gas around the planet.
Problem: these chunks would been ground down in size by
impacts with small dust particles that orbit the Sun. The
ground up remains would have lost angular momentum from
pressure from sunlight, and they gradually would have
spiraled into the planet
Origin of Rings
Enceladus
Juno
• Theory 3: the ring particles
originate from small moonlets
which are being ground up by
impacts with dust sized
particles, or through occasional
impacts with larger objects.
• The majority of the ring
particles are young and
reflective
• Continuous replenishment from
moonlets
• Consequence: the ring may
look very different in the future
• Arrival date: 4 July 2016
• Goal: Reveal the story of the formation and evolution of Jupiter
• … through magnetic fields, atmospheric dynamics and
composition.
• Stay tuned.
http://solarsystem.nasa.gov/missions/juno/indepth
Where are the Voyager Spacecraft?
Deep Space Network – Antenna
locations
http://voyager.jpl.nasa.gov
• Voyager 1 (137 AU from Sun) & 2 (112 AU) continue to
transmit signals back to Earth.
• Voyager 1 entered interstellar space in August 2012
• They are continuously monitored by the Deep Space Network
• Present Voyager mission – Find the edge of the Solar System (Video)
The Golden Record
The Golden Record
• A Gold-plated phonograph record
was placed in each Voyager
• Intent: to show the story of Earth
to extraterrestrials through sounds
and images portraying the diversity
of life and cultures of Earth
• Record, cartridge and needle are
encased in aluminum jacket.
Symbolic instructions on origin of
spacecraft and directions on how
to place the record included
• Time till closest approach to
another planetary system = 40,000
yrs
http://voyager.jpl.nasa.gov/spacecraft/goldenrec.html
The Golden Record
• Example of included photographs: Solar system parameters
(Frank Drake)
http://voyager.jpl.nasa.gov/spacecraft/scenes.html
http://voyager.jpl.nasa.gov/spacecraft/goldenrec_more.html