Download 20 Planetology07aaa0

Geology 12
Planetology
Unit 5

Outline
 A: Origin of Solar System
 B: Planets
 C: Moons
A: Origin of Solar System
Big Bang
13.7 billion yrs ago
0 – 300,000 years: light elements (H2 and
He) form (was 100% H2 & He; now 98%)
 300 ma: Universe continued expanding
forming 1st stars (13.4 ba) and galaxies
(Quasars = developing galaxy)
 Stars produced heavier elements via
fusion (Li – Fe) and exploding (super
novas)

1st Stars
Nebula
1st Galaxies

Solar Nebular Theory:
 Deals with the creation of solar system
1. Swirling eddy cloud of dust and gas
within the galaxy coalesces into a
whirlpool.
2. As the whirlpool spins, it shrinks spinning
faster finally into a spinning flat disc.
3. 90+ % of the mass concentrates at the
centre to form an embryonic sun (protostar) which emits light/heat and solar
(hydrogen nuclei) wind
4. The Sun’s solar wind coupled with all the
ionized gasses in the rotating disc caused
a magnetic braking effect (Sun now
rotates once/25 days) slowing disc down
to moderate speeds.
Ionized
gasses
Sun
Lines of
Magnetic
force
5. Sun’s heat warmed inner disc so lighter
elements could not condense so solar
wind pushes most of these elements out to
form gas giant planets.
gaseous
rocky
M VEM
Inner
C
J
S
U
Outer planets
Planets
Hot
N
Cold
frozen
E
P
Solar Nebular Theory
Solar Nebular Theory
6. <10% of the mass accretes into larger
and larger particles which eventually
form planetesimals (60 – 100). As the
planetesimals collided, they grew in size
and mass (gravitational attraction), but
fewer in number, to form the planets.
 Large collisions among planetesimals
resulted in:
a)
b)
Venus spinning backward very slowly
Uranus & Pluto spin on their side
Two planetisimals colliding
Orbits
Orbits

Asteroids: left over planetesimals
 Most between Mars and Jupiter
(Jupiter’s gravity prevented formation
of small planet).
Now a dwarf planet

Comets: formed near Uranus and
Neptune; the immense gravitational pull of
Saturn and Jupiter has created their highly
elliptical orbits that range from the Sun to
the Oort Cloud at the edge of the Solar
System.
Sun to Earth = 1 A.U. = dist’ Earth to Sun: 150 m km
Sun to Pluto: 39 A.U.
Sun to edge of Solar
System: 35,000 A.U.
Comets
Comets
Oort Cloud
Oort Cloud

Final Result:
1. All planets revolve around the Sun in
same direction: CCW (Q.10, p.6)
2. Nearly all planets (‘cept Venus), moons
orbit and spin/rotate in same direction:
CCW
3. Nearly all axes of rotation are
perpendicular to plane of revolution
(Plane of the Ecliptic)
90’
90’
4. a) Terrestrial Planets: are small, rocky,
high densities (4 – 5.5 gm/cm3) and
metallic element (light elements blown…)
b) Gaseous Planets: large, low densities
(0.7– 1.7 gm/cm3 ) and mostly frozen
compounds (cold, little solar wind)
5. Slow rotation of Sun (slowed by magnetic
braking)
6. Asteroid belt between Mars and Jupiter (left
over pieces of early Solar System)
Solar System
B: Planets
Two Types:
Terrestrial
and
Jovian/Gas Giant
Hand out data table on Planets
Terrestrial Planets
Terrestrial Planets
Metallic cores, silicate mantle-crust
differentiated by volcanism and meteorite
cratering
 Atmosphere produced by volcanic
outgassing
 High densities: SG 4 – 5.5
 Slow rotators: 24+ hrs/day
 Weak magnetic fields
 Few, if any moons

Planets:
Mercury
4880 km
1. Mercury
 Smallest planet (slightly larger than our moon)
 Closest to Sun (hot on sunny side; cold on
shady side + long days: 1 M-day = 58 E-days)
 Weak gravity and high temperatures caused loss
of atmosphere to space
 Radioactive heat expired long ago causing
contraction of planet leading to normal
faulting…heavy cratering over faults indicates
cooling occurred long ago. (dating via principle
of cross-cutting)
Normal fault
Mercury: craters & lava
flows
Venus
2. Venus (Earth’s sister/twin planet)
because it’s the same size.
 Shrouded in thick clouds of CO2 and N2.
(90x Earth’s pressure)
 Very hot (+450’C) with runaway
greenhouse effect.
 Active volcanism, folded mountains, faults,
trenches indicate tectonic activity.
 No magnetic field
 Rotates backwards 1 V-day = 243 E-days
Venus
12100 km
Earth
12800 km
3. Earth
 Active volcanism, folded mountains, faults,
trenches indicates tectonic activity
 Plate tectonics, oceans and weathering
covers up meteorite impacts
Mars
4. Mars
 ½ Earth’s diameter; twice Moon’s
 Billions of years ago its volcanic
outgassing provided ample CO2 and water
for oceans. CO2 greenhouse effect
warmed Mars so oceans flowed in great
seasonal floods cutting immense canyons
(and water depositional features).
Volcanic activity slowed/ceased long ago
(3.5 ba), CO2 atmosphere was lost to
space, planet cooled and water froze.

Now frozen desert with wind storms and
dunes.
 N-hemisphere: large smooth plains,
extensive volcanism (Olympus Mons:
largest known volcano in Solar System),
and few craters.
 S-hemisphere: heavily cratered from
meteorite bombardment (Hellas: 2000 km
crater is largest known in Solar System).

Mars
6800 km
Mar’s N-pole
Mar’s breccia & debris
Canyon: Valles Mariness
Olympus Mons
Olympus Mons
Face of Mars
Mars wind storm
What kind of dunes are those?
Longitudinal dunes
Jovian Planets/Gas Giants
3 layer structure: rocky cores, liquid
mantle, H2-He (+methane and ammonia)
atmosphere topped by clouds
 All have rings
 Strong magnetic fields
 Low density: 0.7 – 2.0
 Fast rotators: <17 hrs to a day
 Many moons

Jupiter
142800 km
5. Jupiter
 Largest planet
 Liquid mantle of metallic hydrogen creates
very strong magnetic field
 Emits 2.5 x more energy than it receives
(heated by compaction-compresson 5 ba
ago and is still cooling off).
 Faint ring + 16 moons

Rotates very fast -> oblate spheroid:
(10hr day)
Saturn
6. Saturn
 BIG rings and 22 moons
 Emits 2.2 x more energy than it receives
 Similar structure to Jupiter
 10 hr day
120660 km
Uranus
50800 km
7. Uranus
 9 faint rings
 15 small moons
 Rotates on its side (was hit by Earth-sized
object) which when the magnetic field is
measured, gives a precise rotation rate
(hard to measure on gaseous planets).
Magnetic field
Axis of rotation
Dense rocky core surrounded by deep
global ocean of water
 17 hr day

Neptune
8. Neptune
 3 faint rings
 Very stormy (up to 2000 km/hr winds)
despite great distance from Sun???
 Rocky core surrounded by slushy water
and liquid methane ocean
 16 hr day
Neptune
48600 km
Dwarf Planets
1 Terrestrial Dwarf Planet: Ceres
 Rocky, no atmosphere
 Hi SG: 3-4
2 Ice Dwarf Planets: Pluto & Eris (but up to
50 outer bodies may fit classification)
 Frozen H2 + He (+methane & ammonia)
 Periodic faint to no atmosphere
 Low SG: 2
Ceres

1000 km diameter (Texas size)
Ceres
Pluto
2350 km
Pluto
 2/3 diameter of Moon (2350 km diameter)
 Highly elliptical orbit crosses Neptune’s
1999
Neptune’s orbit
Sun
1980
Eris (formerly called 2003 UB313 and Xena)
 2500 km diameter
Quaoar: one of many (approx’ 50)
frozen objects beyond Pluto, some
larger than Pluto.
1250km
Terrestrial Planets
All the Planets
Sun vs. Planets
Our Sun vs. Other Stars
Our Sun vs. Other Even
Larger Stars
C: Moons (Natural Satelites)
Mercury and Venus: no moons
 Earth: the Moon
 Rotates on axis and circles Earth 1/month
(27.3 days)
 Surface has two major parts
a) Highlands: light coloured (Fs), oldest (4
ba), heavily cratered
b) Maria (sea): dark-coloured basaltic lava
flows (3.8 – 3.2 ba ago)
Since then nothing but meteorite impacts

Moon
Moon
Anorthosite Fs 4.5 by
Basalt Flows 3.2-3.8 by

Meteorite Impacts

20 m meteorite traveling @ 10 km/s can
excavate a crater 600 m across!
That’s only 23,000 mph (36,000 km/h)
1. Impact and immense heat from pressure and
internal friction.
Shock wave
2. Compressional rebound
ejecta
3. Result: impact crater
Fallback
breccia
ejecta (breccia
and dust)
Fractured
floor
Top View
Raised centre
Ejecta
blanket


Relative dating: what’s on top is
youngest = superposition
3 kinds of material on surface
1.
2.
Igneous rocks: basalt (lava flows)
Breccia
+ Glass sphericules: result
of shock metmorphism
3.
dust
Result of
meteorite
impacts

Moon
Formed from collision with a Mars-sized
planetesimal with Earth about 4.5 ba.
 Molten rock of Moon lost most of its water
(only ice is at S-pole believed from an icy
meteorite impact)
 Moonquakes indicate:

 100
km crust
 Plastic and liquid mantle
 Small solid core

Moonquakes caused by cooling and
shrinking mantle (normal faults)
Impact Craters
Ejecta Blanket
Impact Craters
Raised centre
Berringer Crater, Arizona
The object which excavated the crater was a
The
crater
was lies
created
50,000
years
nickel-iron
meteorite
about
50 meters
yards)
Meteor
Crater
at
anabout
elevation
of (54
about
ago during
theimpacted
Pleistocene
when
the of
across,
plain
aisspeed
1740
m which
(5709
ft)
above the
seaepoch
level.atIt
about
local climate
onft)
the
Plateau
was
several
kilometers
per
second. The
speed
of
1,200
m
(4,000
inColorado
diameter,
some
170
m the
much
cooler
and
damper.
At
the
time,
the
impact
has
been
a
subject
of
some
debate.
deep (570 ft), and is surrounded by a rim that
area 45
wasm
an
open
grassland
dotted
with
Modelling
initially
suggested
that
the meteorite
rises
(150
ft)
above
the
surrounding
woodlands
mammoths,
struck The
at ainhabited
speed of
of by
up woolly
to
20 kilometers
per
plains.
center
the
crater
is filled with
giant(45,000
ground
sloths,ft)but
and
camels.
It was
second
mph),
recent
research
210-240
m (700-800
of more
rubble
lying
above
uninhabited
by
humans,
the first of whom
suggests
the impact
was
substantially
slower, at
crater
bedrock.
are thought
to have
reached(28,600
North America
12.8
kilometers
per second
mph). It is
only around
13,000
believed
that about
half years
of the ago.
impactor's
300,000 tonne (330,000 short tons) bulk was
vaporized during its descent, before it hit the
ground.
Permian Extinction

80% of species wiped out
Cretaceous Extinction

50% of species wiped out
Continental Shelf
To Can Cun
Land
3d gravity Anomaly of impact crater

Mars: 2 small, irregular shaped moons
1. Demos: 8 km long
2. Phobos: 27 km long, circles Mars/8hrs and
will crash in 20 ma
Mars Moon: Deimos
Mars Moon: Phobos
Jupiters Moons

Jupiter (18 moons)
 4 large moons
1. Io: very close to Jupiter causing
huge land tides (+90km) causing
tremendous internal friction…this heat
leads to intense volcanic activity ->
sulphur volcanoes
Io
Io
Io
“Gravitational tug of war”
Io
volcanic plume
2. Europa: 2nd closest moon
Large tides also cause internal
friction…enough to melt
water…so…Europa has thick
oceans of convecting water
covered by ice.
Europa
Europa ice cracks
Ice
Oceans
Solid Rocky Mantle ?
Core ?
3. Ganymede: grooves (ridges and
valleys) that are younger than craters
suggesting?? Ice crustal plates??
4. Callistro: most cratered object in
Solar System
Both
largely frozen ice with silicate
rocky cores.
Ganymede
Largest moon in
SS
Grooves, ridges of ice?
Callisto
 Saturn
(22 moons)
Titan: atmosphere of hydrocarbons
and nitrogen; oceans of hydrocarbons
½ rocks and ½ frozen water
N2 atmosphere
Landed there 2 yrs ago
Titan
2nd largest moon in SS
Titan
Titan’s
surface

Uranus (15 moons)
 Small
 Miranda: bizarre V-shaped grooves
Miranda
Miranda
V-groove:
Plate Tectonics?
Meteorite impact?
Shrinkage?

Neptune (8 moons)
 Triton
Largest moon of Neptune
Volcanic activity (geysers of carbonrich material of N2)
Probably a captured planet (same
size as Pluto)
Triton
Triton
Triton’s surface
Nitrogen geyser
Nitrogen
geyser
 Pluto
(3 moons)
Charon
½ size of Pluto

Eris: 1 moon called Dysnomia
Do WS 20.1