Download Why do the terrestrial planets have different geological have

Why do the terrestrial planets
have different geological
histories?
Role of Planetary Size
• 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
Role of Distance from Sun
• Pl
Planets
t close
l
tto Sun
S are too
t hot
h t for
f rain,
i snow,
ice and so have less erosion
• More difficult for hot planet to retain
atmosphere
• Planets far from Sun are too cold for rain,,
limiting erosion
• Planets with liquid water have most erosion
Role of 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
Thought Question
How does the cooling of planets and potatoes
vary with size?
a) Larger makes it harder for heat from inside
to
escape
b) Larger has a bigger ratio of volume (which
needs to cool) to surface area (the surface is
where cooling
happens)
c) Larger takes longer to cool
d) All off the
th above
b
Thought Question
How does the cooling of planets and potatoes
vary
with size?
a) Larger makes it harder for heat from inside
to
escape
b) Larger has a bigger ratio of volume (which
needs to cool) to surface area (the surface is
where cooling
happens)
c) Larger takes longer to cool
d) All off the
th above
b
How do impact craters reveal a
surface’s geological age?
History of Cratering
• Most cratering
happened in
y
first billion years
• A surface with
many craters
has not
changed much
in 3 billion years
Cratering of Moon
• Some areas of
Moon are more
y cratered
heavily
than others
• Younger regions
y
were flooded by
lava after most
cratering
Cratering of Moon
Cratering map of Moon’s entire surface
9.3 Geology of the Moon and Mercury
Our goals for learning:
• What geological processes shaped our
Moon?
• What geological processes shaped
M
Mercury?
?
What geological processes
shaped our Moon?
Lunar Maria
• Smooth, dark
lunar maria are
y
less heavily
cratered than
lunar highlands
• Maria were
made by flood
of runny lava
Formation of Lunar Maria
Early surface Large impact
covered with crater
craters
weakens
crust
Heat buildbuildup allows
lava to well
up to surface
Cooled lava
is smoother
and darker
than
surroundings
Tectonic Features
• Wrinkles arise
from cooling
and contraction
of lava flood
Geologically Dead
• Moon is
considered
g
geologically
g
y
“dead” because
geological
processes have
h
virtually stopped
What geological processes
shaped Mercury?
Cratering of Mercury
• A mixture of heavily cratered and smooth
regions like the Moon
• Smooth regions are likely ancient lava flows
Cratering of Mercury
Caloris basin is
largest impact crater
on Mercury
Region opposite
Caloris Basin is
jumbled from
seismic energy of
impact
Tectonics on Mercury
• Long
g cliffs indicate that Mercury
y shrank early
y in
its history
9.5 Geology of Venus
Our goals for learning:
• What are the major geological features of
Venus?
• Does Venus have plate tectonics?
What are the major geological
features of Venus?
Radar Mapping
• Thick atmosphere forces us to explore Venus’
surface through radar mapping
Scattered
impact craters
Volcanic regions
Smooth lava flows
Radar maps Venus’s Surface
Cratering on Venus
• Impact craters,
craters but
fewer than Moon,
Mercury, Mars
Volcanoes on
Venus
Many
volcanoes,,
including both
shield
volcanoes and
stratovolcanoes
Shield Volcanoes
Found above
hot spots:
Fluid magma
chamber from
chamber,
which lava erupts
repeatedly through
surface layers
y
above.
All volcanoes on Venus and Mars are shield volcanoes
Not from subduction zones
Shield Volcanoes (2)
Tectonic plates moving over hot spots producing
shield volcanoes  Chains of volcanoes
Venus and Mars types
Example: The
H
Hawaiian
ii IIslands
l d
Volcanism on Venus
Sapas Mons (radar image)
3D computer generated
~ 400 km (250 miles)
2 la
lava-filled
a filled calderas
Lava flows
Tectonic Features on Venus
Aine
Corona
• Fractured and
contorted surface
indicates tectonic
stresses
Coronae: Circular bulges formed by
volcanic activity
Pancake
P
k
Domes:
Associated
with volcanic
activity forming
coronae
Wide angle shot of Corona area
Erosion on Venus
• Photos of
rocks taken byy
lander show
little erosion
Does Venus have plate
tectonics?
•
•
Most of Earth’s
Earth s major geological features
can be attributed to plate tectonics,
gradually
y remakes Earth’s surface
which g
Venus does not appear to have plate
tectonics, but entire surface seems to
have been “repaved” 750 million years
ago
9.4 Geology of Mars
Our goals for learning:
• How did Martians invade popular culture?
• What
Wh t are the
th major
j geological
l i l ffeatures
t
off
Mars?
• What geological evidence tells us that
water once flowed on Mars?
How did Martians invade
popular culture?
“Canals”
Canals on Mars
• Percival Lowell misinterpreted surface features
seen in telescopic images of Mars
Pathfinder lander becomes
The Sagan Memorial Station
View form Sojourner rover
Cratering on Mars
• Amount of cratering
g differs g
greatly
y across
surface
• Many early craters have been erased
Volcanism on Mars
• Mars has many
large shield
volcanoes
• Olympus Mons
is largest
volcano in solar
system
Hidden Water on Mars
No liquid water on the surface:
Would evaporate due to
low pressure.
pressure
But evidence for liquid water
in the past:
O tfl
Outflow
channels
h
l ffrom sudden,
dd
massive floods
Collapsed structures after
withdrawal of sub-surface water
Valleys
y resembling
g
meandering river beds
Gullies, possibly from debris flows
Central channel in a valley
suggests long-term flowing water
Valles Marineris, Viking, close up, the grand canyon of Mars, canyon's
central regions
regions, depressions are called chasmata.
chasmata Surface
S rface collapse and
landslides revealed also layered deposits within the canyon system.
full width OF IMAGE = 800 kilometers
Dry Riverbeds?
• Close-up
photos of
Mars show
what appear
to be dried-up
riverbeds
Unusual Gullies and Channels on Mars
Many scientists hypothesize that liquid groundwater can sometimes surface on Mars, erode gullies and
channels, and pool at the bottom before freezing and evaporating.
frost
Sand dunes
Many scientist conclude, Life-sustaining ice and water might exist, even
today, below the Martian surface from the presence of these young Gullies
Hidden Water on Mars (2)
Hematite concretions
in Martian Rocks,
photographed by the
Mars Rover
Opportunity
Sedimentary rock
layers formed by
layers,
rapidly flowing
water.
Martian Rocks
• Mars rovers have found rocks that appear to
have formed in water
Erosion of Craters
• Details of
some craters
gg
they
y
suggest
were once
filled with
water
t
SKI MARS
3/8ths Earth's gravity
The south pole. (MGS) In spring shrinks from sublimation. Hazy clouds of ice crystals and fog
abound. Overall, cap has been dwindling and increasing atmospheric pressure
A scenario based on elevation data recorded by the MOLA (Mars Orbiter Laser Altimeter) on Mars Global Surveyor
Three and a half billion years ago in the southern highlands.
Largest lake spilled - torrential floods, carved the sinuous
Ma'adim Vallis one of the largest canyons.
Ancient
waters
Of
Mars
Hydrogen Content
• Map of hydrogen content (blue) shows that low
lowlying areas contain more water ice
Crater Walls
• Gullies on crater
walls suggest
q
occasional liquid
water flows
have happened
l
less
th
than a
million years
ago
Early picture of surface!
Looks just like Prof. Robbins
Mars Global Surveyor close-up of the “FACE” .
Such complex looking landforms in the Cydonia
region are thought to be the result of erosion and
weatheringg of ancient crust by
y Martian winds,,
frost, and possibly surface water
A true face on mars
Large impact like this sent
pieces of Mars into space and
eventually
t ll some off them
th
landed on Earth
Meteorite ALH84001:
Identified
As coming from Mars
Some minerals
S
i
l in
i this
thi meteorite
t it were deposited
d
it d in
i water
t 
Martian crust must have been richer in water than it is today.
Life in our
Solar System?
From
MARS
!
NASA &
Stanford
scientists:
i i
“Contains
fossils
of ancient
Martian life”
Events indicates that the meteorite was catapulted from Mars during a huge impact
16 million years ago, fell to Earth's Antarctica 13,000 years ago.
Microscopic carbonate
Globules resemble terra
Bacterial deposits
TUBES
Resemble
Earthly
B t i
Bacteria
features
Mars? Minute pockets of gases
identical in isotopic composition
to the Martian atmosphere from
the Viking measurements
Claimed to live over 3.6
3 6 billion years ago.
ago Fossil measures less than
1/100th the width of a human hair. Support evidence includes organic
molecules and mineral features characteristic of biological activity
NGM MARS
THE FUTURE?
Tickets available in the lobby !
9.6 Review of the Unique Geology of
E th
Earth
Our goals for learning:
• How do we know Earth’s surface is in
motion?
• How is Earth’s surface shaped by plate
t t i ?
tectonics?
• Was Earth’s geology destined from birth?
How do we know Earth’s
surface is in motion?
Continental Motion
• Motion of continents can be measured with
GPS
Continental Motion
• Idea of
continental drift
p
by
y
was inspired
puzzle-like fit of
continents
• Mantle material
erupts where
seafloor
spreads
d
Seafloor Crust
• Thin seafloor
crust differs
from thick
continental crust
• Dating of
seafloor shows
it is usually quite
young
How is Earth’s surface shaped
by plate tectonics?
Seafloor Recycling
• Seafloor is recycled through a process
known as subduction
Surface Features
• Major
geological
features of
North America
record history
off plate
l t
tectonics
Surface Features
• Himalayas are
forming from a
collision
between plates
Surface Features
• Red Sea is
forming where
plates are
p
pulling apart
Rifts Faults,
Rifts,
Faults Earthquakes
• San Andreas
fault in
California is a
plate boundary
• Motion of
plates causes
p
earthquakes
Hot Spots
• Hawaiian islands have formed where plate
is mo
moving
ing o
over
er volcanic
olcanic hot spot
Was Earth’s geology destined
from birth?
Earth’ss Destiny
Earth
• Many of Earth
Earth’s
s
features
y
determined by
size, rotation,
and distance
f
from
Sun
S
• Reason for plate
tectonics not yet
clear
l
The Planet Earth is full of Life…..but that’s another story!