Chapter 891011 Part 3

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Chapter 891011 Part 3 Planets in
General Standard Plane Comparative Planetology
Hartmann Chapters 8 Planetary Interiors
9 Planetary Surfaces
10 Planetary
Surfaces 11
Planetary Atmospheres
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Comparative Planetology
Formation history Interior geological
activity Atmosphere atmospheric
activity Magnetic field magnetic field
activity Role of Planetary Size Role of Distance
from Sun Role of Rotation
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Comparative Planetology
Formation history Interior geological
activity
Four basic properties of a planet mass
diameter mean density surface rock
properties
Basic concept is to use the surface features
materials as observational boundary conditions
then reason out the interior of the planet based
on our knowledge of how these materials behave
under high pressure and how resulting surface
features are formed.
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Processes that Shape Surfaces

• Impact cratering
• Impacts by asteroids or comets
• Volcanism
• Eruption of molten rock onto surface
• Tectonics
• Disruption of a planets surface by internal
  stresses
• Erosion
• Surface changes made by wind, water, or ice

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Comparative Planetology
Impact Cratering Volcanism (lava,
outgassing) Cliffs Mountains
tectonics Plains Ice Caps Magnetic
field Rotation Distance from Sun Heating
/Cooling of Interior Erosion (water, ice, wind,
debris)
Craters Volcanoes Cliffs Mountains Plains Ice
Caps Magnetic field Axis tilt
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Source of volcanism .
Core, Mantle, Crust, AtmosphereAll terrestrial
planets have a similar structure
a liquid core a mantle of molten lava
a crust od solid, low-density rocks
an atmosphere (large range of
compositions and pressures)
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Comparative Planetology
Impact Cratering Volcanism (lava,
outgassing) Cliffs Mountains
tectonics Plains Ice Caps Magnetic
field Rotation Distance from Sun Heating
/Cooling of Interior Erosion (water, ice, wind,
debris)
Craters Volcanoes Cliffs Mountains Plains Ice
Caps Magnetic field Axis tilt
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The Highlands on the Moon
Saturated with craters
Older craters partially obliterated by more
recent impacts
or flooded by lava flows
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mi
6.68 5.45 2.97 1.74 -0.74 -3.21 -5.69
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Hadley Rille-Apennine mountain region at 26 deg
06 min 54 sec N, 3 deg 39 min 30 sec E on the
lunar surface. The lunar module (LM) carrying
astronauts David Scott and James Irwin and the
lunar roving vehicle (LRV) landed on the moon on
July 31, 1971. http//www.penpal.ru/astro/Apollo15
.shtml
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lobate scarps are long, steep curved cliffs,
probably formed when Mercury shrank while cooling
down
Discovery Scarp
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Discovery scarp 500 km long, 2 km
high Mercurys crust split and cracked as the
planet cooled and shrank
lobate scarps
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Two Geological features on Mercury worth
mentioning
2. lobate scarps are landforms on Mercury that
appear to have formed by thrust faulting and
are thought to reflect global contraction
due to cooling of the planet's interior
(like a drying apple)
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Radargraphs Using radar, the topography
(surface features) of Venus is imaged.
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Radar images showed a relatively flat Venus with
some highlands two continental-sized areas of
higher elevation terrain is comprised of 10
mountain, 70 upland plains, 20 lowland plains
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Role of Planetary Size Role of Distance from
Sun Role of Rotation

• Smaller worlds cool off faster and harden earlier
• Larger worlds remain warm inside, promoting
  volcanism and tectonics
• Larger worlds also have more erosion because
  their gravity retains an atmosphere

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Role of Planetary Size Role of Distance from
Sun Role of Rotation
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Role of Planetary Size Role of Distance from
Sun Role of Rotation

• Planets close to Sun are too hot for rain, snow,
  ice and so have less erosion
• More difficult for hot planet to retain
  atmosphere
• Planets with liquid water have most erosion
• Planets far from Sun are too cold for rain,
  limiting erosion

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Role of Planetary Size Role of Distance from
Sun Role of Rotation
Habitable Zone for Constant Liquid Water in the
Solar System
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Role of Planetary Size Role of Distance from
Sun Role of Rotation
Slow rotation
Fast rotation

• Planets with slower rotation have less weather
  and less erosion and a weak magnetic field
• Planets with faster rotation have more weather
  and more erosion and a stronger magnetic field

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Other Observational that Check the Models for
Planet Interiors moment of inertia
kMR2 , k being coefficient of 0. 1.
geometric oblateness reflects mass distribution
or departure from hydrostatic equilibrium
form of gravitational field rotation rate
necessary for moment of inertia, geometric
oblateness surface heat flow composition
of neighbors (planets and or meteorites)
magnetic field strong field indicates a flluid
core drilling and direct sampling seismic
properties

Earth
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Comparative Planetology
Impact Cratering Volcanism (lava,
outgassing) Cliffs Mountains
tectonics Plains Ice Caps Magnetic
field Rotation Distance from Sun Heating
/Cooling of Interior Erosion (water, ice, wind,
debris)
Craters Volcanoes Cliffs Mountains Plains Ice
Caps Magnetic field Axis tilt
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The Earths Magnetic Field is created in the same
way you make an electromagnet
In an electromagnet the electrons move around an
iron nail
education.gsfc.nasa.gov/nycri/units/pmarchase/
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A planet with a magnetic field indicates a
fluidinterior in motion

• Planetary magnetic fields are produced by the
  motion of electrically conducting liquids inside
  the planet
• This mechanism is called a dynamo
• If a planet has no magnetic field, that is
  evidence that there is little such liquid
  material in the planets interior or that the
  liquid is not in a state of motion

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• The magnetic fields of terrestrial planets are
  produced by metals such as iron in the liquid
  state
• The stronger fields of the Jovian planets are
  generated by liquid metallic hydrogen or by water
  with ionized molecules dissolved in it

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Main Worlds with Active Magnetic Fields
Strength Order Sun, Gas giants, Earth,
Mercury, Mars (remnant)
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The Earth is made of four layers
The Crust A Thin Rock Material
The Mantle A Dense and Mostly Solid Rock Material
The Outer Core Liquid Iron and Nickel
The Inner Core Solid Iron and Nickel
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The Iron Core of the Earth is an Electromagnet
The core is surrounded by liquid Iron and Nickel
As electrons flow around the core the magnetic
field is produced
The Earths rotation makes the electrons flow at
very high speeds
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Magnetic Fields on Other Planets in our Solar
System
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Mercury
Mercury has a weak magnetic field. This suggests
Mercury has an iron core with liquid
interior. The weak magnetic field could be the
result of the slow rotation period.
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Venus
Venus has a very weak magnetic field. (About
25,000 times weaker than Earths) Venus appears
to lack the necessary ingredients to generate a
magnetic field (no liquid core?) Venus also has
very slow rotation.
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Mars
Mars also has a very weak magnetic field. (About
5,000 times weaker than Earths)
The interior of Mars appears to have cooled so
much that it is no longer liquid.

• The volcanoes in Mars are no longer active

• There is no Earthquake activity on Mars

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Jupiter
Jupiter has a strong magnetic field. (About
20,000 times stronger than Earths)
The Terrestrial planets generate magnetic fields
from iron at the center. But Jupiter has almost
no iron core.
The magnetic field of Jupiter is produced by the
motion of liquefied metallic hydrogen found
beneath the surface.
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Saturn
Saturn also has a strong magnetic field. (About
540 times stronger than Earths)
Saturns magnetic field is produced in the same
way Jupiters is.
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Uranus
The magnetic field in Uranus is about 40 times
stronger than Earths
It is probably created in the core of the planet,
with ice, rather than with iron.
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Neptune
The magnetic field in Uranus is about 1/4 times
as strong as Earths
It is probably created in the same way as Uranus
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Pluto
We do not know if Pluto has a magnetic field.
Because Pluto has a small size and a slow
rotation rate (1 day in Pluto 6.4 Earth days),
it does not seem likely that Pluto has a magnetic
field.