Transcript Planetary Surfaces

Planetary Surfaces
What do worlds look like and why?
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Planetary Surfaces
• Even though the terrestrial planets are similar,
their surfaces look different
• What processes shape the surface of a world?
• How do they work?
• How can we infer something about a planet based
on its surface features?
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Describe this feature
• What is this?
• Circular feature
• Thick region of bright
material surrounding
almost perfectly circular
feature
• Outside edge of bright
material ragged, not
circular
• Central peak of bright
material in center
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Describe this feature
• What is this?
• Dark,
sinuous
lines
emanating
radially
from a
central,
almost
circular,
depression
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Rocks
• Rocks are
made of
minerals
• Types of rocks:
– Igneous rocks are those that have formed from a
molten state (volcano made)
– Sedimentary rocks are composed of fragments
of other rocks that are cemented together (water made)
– Metamorphic rocks are produced from either igneous
or sedimentary rocks that have been buried and
modified by high temperatures and pressures
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Why does the earth look like this?
Processes that alter the
surface of the earth:
• Endogenic
– Forces that act from
inside the earth:
• Volcanic
• Erosional
• Tectonic
– These forces can make
rocks
• Exogenic
– Forces that act from
outside the earth:
• Cratering
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Tectonics
Any movement of
the earth
–
–
–
–
Folding
Fracturing
Earthquakes
Plate tectonics
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Plate Tectonics
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• Tectonics is NOT just
plate tectonics.
• Plate tectonics is a
KIND of tectonics.
• Other planets have
tectonics, but only the
Earth has plate
tectonics.
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Tectonics
• Features tend to be linear
• Features are occasionally
curvilinear
• Features often occur in
groups or sets
• Special Case: Venus
– Coronae are circular to
quasicicular, but they are
tectonic
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Volcanoes
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Volcanoes
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Venusian volcanoes
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Martian volcanoes
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• Only two places in the solar
system have active volcanoes:
– Earth
– Io
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Volcanoes
• Volcanoes are
generally circular to
quasicircular
• Lava flows are
sinuous and have
highly irregular
margins, often
organic looking
• Flows generally
originate from a
single point
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Erosion
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Erosion
• Features tend to
be sinuous
(curving back
and forth)
• Features tend
to occur in groups
• Interior features appear
teardrop shaped
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Impact Craters
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Impact craters
• Circular feature, never
quasi-circular
• Often contain central peak,
central ring, ejecta blanket
• Special case: Mars
– Rampart, or “splosh” craters
have watery ejecta blankets
and are found only on Mars
• The more impact craters,
the older the surface
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Comparative Planetology
• 4 main surface altering processes
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–
–
–
Cratering (exogenic)
Volcanism (endogenic)
Tectonics (endogenic)
Erosion (endogenic)
• In order for endogenic processes
to occur, energy must be available.
• Small planets (and moons, and asteroids) generally have little internal
heat, and, therefore, little endogenic activity.
• Exogenic processes affect everything.
• The main sources of heat are:
–
–
–
–
Radioactivity
Sunlight
Energy of formation (original heat)
Tidal heating
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Comparative Planetology 2
• The bigger a planetary body is, the more energy is
available to modify it
– Small bodies are irregularly shaped and covered only
with craters (exogenic)
– Slightly bigger bodies are spherical
– Bigger bodies are spherical and differentiated
– The largest bodies are spherical, differentiated, and
have endogenic processes which modify their surfaces
• The exceptions to this rule are close to the Sun, or
close to their parent planet
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What is it? Tips & techniques
• If it is circular, it is most likely a volcano or crater
– Look for lava flows associated with a volcano
– Look for a central peak, peak ring or ejecta blanket on a
crater
• If it’s nearly circular it is probably a volcano
• If it’s linear it’s likely tectonics
– If it’s sinuous, it’s either a lava flow or erosion
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Where is it?
• Tips for identifying location:
– Only the Earth has water on the surface
– Only the Earth and Mars have erosional features
– Venus must be photographed with radar, so the images
look different
– Mercury and the Moon have nothing but craters on
them
– Finally, look for unique features, like
• Coronae
• “Splosh” craters
• Pancake volcanoes
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Describe this feature
• What is this?
• Circular feature
• Thick region of bright
material surrounding
almost perfectly circular
feature
• Outside edge of bright
material ragged, not
circular
• Central peak of bright
material in center
• Impact crater on Venus
10
Describe this feature
• What is this?
• Dark,
sinuous
lines
emanating
radially
from a
central,
almost
circular,
depression
• Volcano on
Earth
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