Transcript 15._planetary_processes_student

Interiors of Worlds
and Heat loss
Differentiation -materials
separate into layers by gravity
How do we learn about
planetary interiors?
•Measure moment of inertia & average density
• Observe seismic events
• Study planetary magnetic fields
Interior of our planet
gaseous atmosphere
(lowest density)
Interior of Terrestrial Worlds
Interiors: Gas Giant v.s Terrestrial
Interior of Gas Giant Worlds
The magnetic
fields of gas
giants indicate
that there are
large amounts
of circulating,
electricallyconducting
materials.
Metallic hydrogen
or water
Which of the following layers of a
planet is not characterized by its
density?
A.core
B.mantle
C.lithosphere
D.crust
E.none of the above
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Heat loss
Planets gain
their initial
internal heat
energy when
they first form
Planet spend the rest of their lives
losing internal energy to space
3 Types of Heat loss
• Conduction -atoms vibrate strongly causing
atoms next them to pick up energy
• Convection- heat causes fluids to move, the
hot fluid rises, the cold fluid sinks.
• Radiation- photons of electromagnetic light
carry energy away from the object
Which Forms of Heat Loss
Work Where?
• All worlds conduct inside.
• All worlds radiate out to space (the only heat
transfer that works in a vacuum!).
• Larger worlds convect inside.
• Largest worlds convect and radiate inside.
(wavelength of radiation depends on world mass)
Solid Convection Causing Volcanism
Solid convection causing
movement, but no crustal break-up
Solid convection causing
crustal break-up (Earth only)
How does an object's rate of
cooling vary with size?
A. A larger object cools more slowly
than a smaller object.
B. A smaller object cools more slowly
than a larger object.
C. Size has no effect on an object's
rate of cooling.
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Geologic Processes
Geological Processes
• Tectonics
– Rocks bend and break (folding and faulting).
• Volcanism
– Materials melt, explode and freeze.
• Erosion and surface processes
– Surfaces flatten out: mountains crumble and holes
are filled in.
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Mass wasting (gravity action)
Wind action
Water action
• Impact Cratering (external)
– Bodies from space hit the ground, making a hole.
Tectonics -Folding
• When rocks are squashed they will compress
and bend away from the direction of maximum
pressure
Tectonics -Faulting
1. Extension Faults -crust moves apart, makes a larger area.
1. Compression Faults -crust moves together, makes smaller area.
1. Strike-slip Faults
-crust moves sideways,
no gain or loss of area
What is true of convection that
stresses a planet's crust?
A. Mountains may form where the crust is
pushed together.
B. Cracks and valleys may form where the
crust is pulled apart.
C. Convection has no effect on a planet's
crust.
D. A and B
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Volcanism
•Materials melt, erupt and explode,
then freeze and coat the surface
Generic Volcano Structure
Volcanic Processes
• Rocks melt and explode.
• 2 components: lava, gasses
• Lavas - variable viscosity,depending on chemistry
• Low viscosity
(runny lava)
range of viscosity
(gooey, sticky lava)
Low gas content
Result:
Low broad shapes
shapes
Volcanic
Shield
Floods
Volcanoes
High viscosity
High gas
Result:
range of volcanoes
Cinder
cones
Tall cone
Stratovolcanoes
Volcanic Floods -VERY low Viscosity
Hawaiian Effusive eruption
Olympus Mons
Martian Shield Volcano
• Note the broad shield
shape and the central
cauldera
Volcanic Processes
• Rocks melt and explode.
• 2 components: lava, gasses
• Lavas - variable viscosity,depending on chemistry
• Low viscosity
(runny lava)
range of viscosity
(gooey, sticky lava)
Low gas content
Result:
Low broad shapes
shapes
Volcanic
Shield
Floods
Volcanoes
High viscosity
High gas
Result:
range of volcanoes
Cinder
cones
Tall cone
Stratovolcanoes
Explosive
Stratovolcanos
• Occur only on Earth
a product of plate tectonics
Alternative Materials
carbonatites,
East Africa, Earth
Water eruption
plume, Enceladus
sulfur
volcanoes,
Io
Erosion and Surface Processes
Gravity pulls everything into a smooth sphere. Thus,
surfaces flatten out: mountains crumble and holes are
filled in.
The processes that carry out erosion each show
characteristic patterns that we can see on Earth and
on different worlds:
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Mass wasting (gravity action)- land slides
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Wind action- sand dunes, wind streaks
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Water action- river channels, ocean shores, glacial erosion
Sand Dunes in the Sahara
(imaged by the Space Shuttle)
Ice/tar dunes on Titan
Water Channels on Mars
Ethane Channels on Titan
Impact Cratering
• Bodies from space hit the ground, making a hole.
(the only external process -it comes to the planet
from the outside)
• The size of the hole depends on the energy of
the impact.
– A small, slow-moving, ice-ball makes a small hole.
– A massive, fast moving, rock makes a large hole.
Imbrium Basin
Moon
Crater Dating
• Solar System debris falls onto planets at a regular
rate, making craters.
• The number of holes on a surface is a measure of
how long it has been exposed to impacts.
• Impact craters can be destroyed by the three
internal processes (tectonics, volcanism, erosion)
• Surfaces with few craters have active processes
destroying the craters. (called YOUNG surfaces)
• Surfaces with lots of craters have no active
processes & are undisturbed. (OLD surfaces)
Which Surface is Older?
B
A
Which World is More Active?
(Be able to explain your choice)
Earth
Moon
Planetary Atmospheres
Atmospheric Basics
• Our goals for learning
• What is an atmosphere?
• How do you obtain an atmosphere?
What is an atmosphere?
An atmosphere is a layer of gas that surrounds a world
How do you obtain an atmosphere?
– Gain volatiles by comet impacts
– outgassing during differentiation
– Ongoing outgassing by volcanoes
Keeping an Atmosphere
• Atmosphere is kept by the world’s gravity and
temperatures
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Low mass (small) worlds = low gravity = little atm.
High mass(large) worlds = high gravity = thick atm.
Low temperatures = slow gases = more atm.
High temperatures =excited gases = atm.loss
• Gravity and pressure
– Air pressure depends on how much weight of
gas is there ie. The atmospheric thickness.
What have we learned?
• What is an atmosphere?
– A layer of gas that surrounds a world
• How do you obtain an atmosphere?
– comet impacts plus outgassing by differentiation,
or volcanoes.
– How much atmosphere is retained depends on
the world’s gravity and temperatures
Atmospheric Processes 1
• Our goals for learning
• What are the key processes?
• What creates wind and weather?
• How does the greenhouse effect warm a
planet?
Atmospheric Processes
• Atmospheric circulation (convection)
– Convection cells move gas from equator to pole and
back.
• Coriolis Effect
– Gas dragged sideways by the rotation rate of the
world.
• Greenhouse Effect
– Infrared energy is re-reflected back to the ground by
CO2
Air Movement
Gas molecules move from high density to lower density
Atmospheric Pressure
Gas pressure
depends on both
density and
temperature.
Adding air
molecules
increases the
pressure in a
balloon.
Heating the air
also increases
the pressure.
(molecules more
energetic)
Atmospheric Circulation
(convection)
• Heated air rises at
equator
Maximum
Sun
warming
• Cooler air
descends at poles
Coriolis Effect
Coriolis Effect breaks up
Global Circulation
• On Earth the large
circulation cell breaks
up into 3 smaller ones,
moving diagonally
• Other worlds have
more or fewer
circulation cells
depending on their
rotation rate
Coriolis
Effect
Winds blow N or S
Venus
Winds are diagonal
Earth
Mars
Winds blow W or E
Jupiter, Saturn
Neptune, Uranus(?)
Greenhouse Effect
If there was no greenhouse
effect, Earth...
A. would be warmer than it is today.
B. would have a thicker atmosphere.
C. would be colder than freezing.
D. would have no protection from ultraviolet
radiation.
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What have we learned?
• What creates wind and weather?
– Atmospheric heating and Coriolis effect.
– Solar warming creates convection cells.
– The coriolis effect drags winds sideways and breaks up
the cells
– The faster a planet spins, the more E-W gas movement
there is
• How does the greenhouse effect warm a planet?
– Atmospheric molecules allow visible sunlight to warm a
planet’s surface but absorb infrared photons, trapping
the heat.