Geology 12 Geology 12 PlanetologyPlanetology

Unit 5Unit 5

OutlineOutlineA: Origin of Solar SystemA: Origin of Solar SystemB: PlanetsB: PlanetsC: MoonsC: Moons

A: Origin of Solar SystemA: Origin of Solar System

Big BangBig Bang13.7 billion yrs ago13.7 billion yrs ago

0 – 300,000 years: light elements (H0 – 300,000 years: light elements (H22 and and

He) form (was 100% HHe) form (was 100% H22 & He; now 98%) & He; now 98%)300 ma: Universe continued expanding 300 ma: Universe continued expanding

forming 1forming 1stst stars (13.4 ba) and galaxies stars (13.4 ba) and galaxies (Quasars = developing galaxy)(Quasars = developing galaxy)

Stars produced heavier elements via Stars produced heavier elements via fusion (Li – Fe) and exploding (super fusion (Li – Fe) and exploding (super novas)novas)

1st Stars1st Stars

NebulaNebula

11stst Galaxies Galaxies

Solar Nebular TheorySolar Nebular Theory::Deals with the creation of solar systemDeals with the creation of solar system

1. Swirling eddy cloud of dust and gas 1. Swirling eddy cloud of dust and gas within the galaxy coalesces into a within the galaxy coalesces into a whirlpool.whirlpool.

2. As the whirlpool spins, it shrinks spinning 2. As the whirlpool spins, it shrinks spinning faster finally into a spinning flat disc.faster finally into a spinning flat disc.

3. 90+ % of the mass concentrates at the 3. 90+ % of the mass concentrates at the centre to form an embryonic sun (proto-centre to form an embryonic sun (proto-star) which emits light/heat and solar star) which emits light/heat and solar (hydrogen nuclei) wind(hydrogen nuclei) wind

4. The Sun’s solar wind coupled with all the 4. The Sun’s solar wind coupled with all the ionized gasses in the rotating disc caused ionized gasses in the rotating disc caused a magnetic braking effect (Sun now a magnetic braking effect (Sun now rotates once/25 days) slowing disc down rotates once/25 days) slowing disc down to moderate speeds.to moderate speeds.

Sun

Lines of Magnetic force

Ionized gasses

5. Sun’s heat warmed inner disc so lighter 5. Sun’s heat warmed inner disc so lighter elements could not condense so solar elements could not condense so solar wind pushes most of these elements out to wind pushes most of these elements out to form gas giant planets.form gas giant planets.

rockygaseous

frozen

Inner

PlanetsOuter planets

M V E USJM N P

Hot Cold

EC

Solar Nebular TheorySolar Nebular TheorySolar Nebular TheorySolar Nebular Theory

6. <10% of the mass accretes into larger 6. <10% of the mass accretes into larger and larger particles which eventually and larger particles which eventually form form planetesimals planetesimals (60 – 100). As the (60 – 100). As the planetesimals collided, they grew in size planetesimals collided, they grew in size and mass (gravitational attraction), but and mass (gravitational attraction), but fewer in number, to form the planets.fewer in number, to form the planets.

Large collisions among planetesimals Large collisions among planetesimals resulted in:resulted in:

a)a) Venus spinning backward very slowlyVenus spinning backward very slowly

b)b) Uranus & Pluto spin on their sideUranus & Pluto spin on their side

Two planetisimals colliding

OrbitsOrbits

OrbitsOrbits

Asteroids: left over planetesimalsAsteroids: left over planetesimalsMost between Mars and Jupiter Most between Mars and Jupiter

(Jupiter’s gravity prevented formation (Jupiter’s gravity prevented formation of small planet).of small planet).

Now a dwarf planet

Comets: formed near Uranus and Comets: formed near Uranus and Neptune; the immense gravitational pull of Neptune; the immense gravitational pull of Saturn and Jupiter has created their highly Saturn and Jupiter has created their highly elliptical orbits that range from the Sun to elliptical orbits that range from the Sun to the Oort Cloud at the edge of the Solar the Oort Cloud at the edge of the Solar System.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.

CometsComets

CometsComets

Oort CloudOort Cloud

Oort CloudOort Cloud

Final Result:Final Result:

1.1. All planets revolve around the Sun in All planets revolve around the Sun in same direction: CCW (Q.10, p.6)same direction: CCW (Q.10, p.6)

2.2. Nearly all planets (‘cept Venus), Nearly all planets (‘cept Venus), moons orbit and spin/rotate in same moons orbit and spin/rotate in same direction: CCWdirection: CCW

3.3. Nearly all axes of rotation are Nearly all axes of rotation are perpendicular to plane of revolution perpendicular to plane of revolution (Plane of the Ecliptic)(Plane of the Ecliptic)

90’

90’

4. 4. a) Terrestrial Planets: are small, rocky, a) Terrestrial Planets: are small, rocky, high densities (4 – 5.5 gm/cmhigh densities (4 – 5.5 gm/cm33) and ) and metallic element (light elements blown…)metallic element (light elements blown…)

b) Gaseous Planets: large, low densities b) Gaseous Planets: large, low densities (0.7– 1.7 gm/cm(0.7– 1.7 gm/cm3 3 ) and mostly frozen ) and mostly frozen compounds (cold, little solar wind)compounds (cold, little solar wind)

5. Slow rotation of Sun (slowed by magnetic 5. Slow rotation of Sun (slowed by magnetic braking)braking)

6. Asteroid belt between Mars and Jupiter (left 6. Asteroid belt between Mars and Jupiter (left over pieces of early Solar System)over pieces of early Solar System)

Solar SystemSolar System

B: PlanetsB: Planets

Hand out data table on Planets

Two Types:

Jovian/Gas Giant

and

Terrestrial

Terrestrial PlanetsTerrestrial Planets

Terrestrial PlanetsTerrestrial PlanetsMetallic cores, silicate mantle-crust Metallic cores, silicate mantle-crust

differentiated by volcanism and meteorite differentiated by volcanism and meteorite crateringcratering

Atmosphere produced by volcanic Atmosphere produced by volcanic outgassingoutgassing

High densities: SG 4 – 5.5High densities: SG 4 – 5.5Slow rotators: 24+ hrs/daySlow rotators: 24+ hrs/dayWeak magnetic fieldsWeak magnetic fieldsFew, if any moonsFew, if any moons

Planets: Planets:

MercuryMercury

4880 km4880 km

1. 1. MercuryMercury Smallest planet (slightly larger than our moon)Smallest planet (slightly larger than our moon) Closest to Sun (hot on sunny side; cold on Closest to Sun (hot on sunny side; cold on

shady side + long days: 1 M-day = 58 E-days)shady side + long days: 1 M-day = 58 E-days) Weak gravity and high temperatures caused loss Weak gravity and high temperatures caused loss

of atmosphere to spaceof atmosphere to space Radioactive heat expired long ago causing Radioactive heat expired long ago causing

contraction of planet leading to normal faulting…contraction of planet leading to normal faulting…heavy cratering over faults indicates cooling heavy cratering over faults indicates cooling occurred long ago. (dating via principle of cross-occurred long ago. (dating via principle of cross-cutting)cutting)

Normal fault

Mercury: craters & lava Mercury: craters & lava flowsflows

VenusVenus

2. 2. VenusVenus (Earth’s sister/twin planet) (Earth’s sister/twin planet) because it’s the same size.because it’s the same size.

Shrouded in thick clouds of COShrouded in thick clouds of CO22 and N and N22. .

(90x Earth’s pressure)(90x Earth’s pressure)Very hot (+450’C) with runaway Very hot (+450’C) with runaway

greenhouse effect.greenhouse effect.Active volcanismActive volcanism, folded mountains, faults, , folded mountains, faults,

trenches indicate tectonic activity.trenches indicate tectonic activity.No magnetic fieldNo magnetic fieldRotates backwards 1 V-day = 243 E-daysRotates backwards 1 V-day = 243 E-days

VenusVenus

12100 km12100 km

EarthEarth

12800 km12800 km

3. 3. EarthEarthActive volcanism, folded mountains, faults, Active volcanism, folded mountains, faults,

trenches indicates tectonic activitytrenches indicates tectonic activityPlate tectonics, oceans and weathering Plate tectonics, oceans and weathering

covers up meteorite impactscovers up meteorite impacts

MarsMars

4. 4. MarsMars½ Earth’s diameter; twice Moon’s½ Earth’s diameter; twice Moon’sBillions of years ago its volcanic Billions of years ago its volcanic

outgassing provided ample COoutgassing provided ample CO22 and water and water for oceans. COfor oceans. CO22 greenhouse effect greenhouse effect warmed Mars so oceans flowed in great warmed Mars so oceans flowed in great seasonal floods cutting immense canyons seasonal floods cutting immense canyons (and water depositional features). (and water depositional features). Volcanic activity slowed/ceased long ago Volcanic activity slowed/ceased long ago (3.5 ba), CO(3.5 ba), CO22 atmosphere was lost to atmosphere was lost to space, planet cooled and water froze.space, planet cooled and water froze.

Now frozen desert with wind storms and Now frozen desert with wind storms and dunes.dunes.

N-hemisphere: large smooth plains, N-hemisphere: large smooth plains, extensive volcanism (Olympus Mons: extensive volcanism (Olympus Mons: largest known volcano in Solar System), largest known volcano in Solar System), and few craters.and few craters.

S-hemisphere: heavily cratered from S-hemisphere: heavily cratered from meteorite bombardment (Hellas: 2000 km meteorite bombardment (Hellas: 2000 km crater is largest known in Solar System).crater is largest known in Solar System).

MarsMars

6800 km6800 km

Mar’s N-poleMar’s N-pole

Mar’s breccia & debrisMar’s breccia & debris

Canyon: Valles MarinessCanyon: Valles Mariness

Olympus MonsOlympus Mons

Olympus MonsOlympus Mons

Face of MarsFace of Mars

Mars wind stormMars wind storm

What kind of dunes are those?

Longitudinal dunes

Jovian Planets/Gas GiantsJovian Planets/Gas Giants

3 layer structure: rocky cores, liquid 3 layer structure: rocky cores, liquid mantle, Hmantle, H22-He (+methane and ammonia) -He (+methane and ammonia)

atmosphere topped by cloudsatmosphere topped by cloudsAll have ringsAll have ringsStrong magnetic fields Strong magnetic fields Low density: 0.7 – 2.0Low density: 0.7 – 2.0Fast rotators: <17 hrs to a dayFast rotators: <17 hrs to a dayMany moonsMany moons

JupiterJupiter

142800 km142800 km

5. 5. JupiterJupiterLargest planetLargest planetLiquid mantle of metallic hydrogen creates Liquid mantle of metallic hydrogen creates

very strong magnetic fieldvery strong magnetic fieldEmits 2.5 x more energy than it receives Emits 2.5 x more energy than it receives

(heated by compaction-compresson 5 ba (heated by compaction-compresson 5 ba ago and is still cooling off).ago and is still cooling off).

Faint ring + 16 moonsFaint ring + 16 moons

Rotates very fast -> oblate spheroid: Rotates very fast -> oblate spheroid:

(10hr day)(10hr day)

SaturnSaturn

6. 6. SaturnSaturnBIG rings and 22 moonsBIG rings and 22 moonsEmits 2.2 x more energy than it receivesEmits 2.2 x more energy than it receivesSimilar structure to JupiterSimilar structure to Jupiter10 hr day10 hr day

120660 km120660 km

UranusUranus

50800 km50800 km

7. 7. UranusUranus9 faint rings9 faint rings15 small moons15 small moonsRotates on its side (was hit by Earth-sized Rotates on its side (was hit by Earth-sized

object) which when the magnetic field is object) which when the magnetic field is measured, gives a precise rotation rate measured, gives a precise rotation rate (hard to measure on gaseous planets).(hard to measure on gaseous planets).

Magnetic field

Axis of rotation

Dense rocky core surrounded by deep Dense rocky core surrounded by deep global ocean of waterglobal ocean of water

17 hr day17 hr day

NeptuneNeptune

8. 8. NeptuneNeptune3 faint rings3 faint ringsVery stormy (up to 2000 km/hr winds) Very stormy (up to 2000 km/hr winds)

despite great distance from Sun???despite great distance from Sun???Rocky core surrounded by slushy water Rocky core surrounded by slushy water

and liquid methane oceanand liquid methane ocean16 hr day16 hr day

48600 km48600 km

NeptuneNeptune

Dwarf PlanetsDwarf Planets

1 Terrestrial Dwarf Planet1 Terrestrial Dwarf Planet: Ceres: CeresRocky, no atmosphereRocky, no atmosphereHi SG: 3-4Hi SG: 3-42 Ice Dwarf Planets2 Ice Dwarf Planets: Pluto & Eris (but up to : Pluto & Eris (but up to

50 outer bodies may fit classification)50 outer bodies may fit classification)Frozen HFrozen H22 + He (+methane & ammonia) + He (+methane & ammonia)Periodic faint to no atmospherePeriodic faint to no atmosphereLow SG: 2 Low SG: 2

CeresCeres

1000 km diameter (Texas size)1000 km diameter (Texas size)

CeresCeres

PlutoPluto

2350 km2350 km

PlutoPluto2/3 diameter of Moon (2350 km diameter)2/3 diameter of Moon (2350 km diameter)Highly elliptical orbit crosses Neptune’sHighly elliptical orbit crosses Neptune’s

SunNeptune’s orbit

1999 1980

Eris Eris (formerly called 2003 UB313 and Xena) (formerly called 2003 UB313 and Xena)2500 km diameter2500 km diameter

QuaoarQuaoar: : one of many (approx’ 50)one of many (approx’ 50) frozen objects beyond Pluto, some frozen objects beyond Pluto, some larger than Pluto.larger than Pluto.

1250km1250km

Terrestrial PlanetsTerrestrial Planets

All the PlanetsAll the Planets

Sun vs. PlanetsSun vs. Planets

Our Sun vs. Other Stars

Our Sun vs. Other Even Larger Stars

C: Moons (Natural Satelites)C: Moons (Natural Satelites)

Mercury and Venus: no moonsMercury and Venus: no moonsEarth: the MoonEarth: the Moon

Rotates on axis and circles Earth 1/month Rotates on axis and circles Earth 1/month (27.3 days)(27.3 days)

Surface has two major partsSurface has two major parts

a) Highlands: light coloured (Fs), oldest (4 a) Highlands: light coloured (Fs), oldest (4 ba), heavily crateredba), heavily cratered

b) Maria (sea): dark-coloured basaltic lava b) Maria (sea): dark-coloured basaltic lava flows (3.8 – 3.2 ba ago)flows (3.8 – 3.2 ba ago)

Since then nothing but meteorite impactsSince then nothing but meteorite impacts

MoonMoon

MoonMoonAnorthosite Fs 4.5 byAnorthosite Fs 4.5 by

Basalt Flows 3.2-3.8 byBasalt Flows 3.2-3.8 by

Meteorite ImpactsMeteorite Impacts20 m meteorite traveling @ 10 km/s can 20 m meteorite traveling @ 10 km/s can

excavate a crater 600 m across!excavate a crater 600 m across!

1. Impact and immense heat from pressure and 1. Impact and immense heat from pressure and internal friction.internal friction.

That’s only 23,000 mph (36,000 km/h)

Shock wave

2. Compressional rebound2. Compressional rebound

ejecta

3. Result: impact crater3. Result: impact crater ejecta (breccia ejecta (breccia and dust)and dust)

Fallback Fallback brecciabreccia

Fractured Fractured floorfloor

Raised centreRaised centre

Ejecta Ejecta blanketblanket

Top View

Relative dating: what’s on top is Relative dating: what’s on top is youngest = superpositionyoungest = superposition

3 kinds of material on surface3 kinds of material on surface1.1. Igneous rocks: basalt (lava flows)Igneous rocks: basalt (lava flows)

2.2. BrecciaBreccia

3.3. dustdust

+ Glass sphericules: result of shock metmorphism

Result of meteorite impacts

MoonMoonFormed from collision with a Mars-sized Formed from collision with a Mars-sized

planetesimal with Earth about 4.5 ba.planetesimal with Earth about 4.5 ba.Molten rock of Moon lost most of its water Molten rock of Moon lost most of its water

(only ice is at S-pole believed from an icy (only ice is at S-pole believed from an icy meteorite impact)meteorite impact)

Moonquakes indicate:Moonquakes indicate:100 km crust100 km crustPlastic and liquid mantlePlastic and liquid mantleSmall solid coreSmall solid core

Moonquakes caused by cooling and Moonquakes caused by cooling and shrinking mantle (normal faults)shrinking mantle (normal faults)

Ejecta BlanketEjecta Blanket

Impact CratersImpact Craters

Impact CratersImpact Craters

Raised centreRaised centre

Meteor Crater lies at an elevation of about 1740 m (5709 ft) above sea level. It is about 1,200 m (4,000 ft) in diameter, some 170 m

deep (570 ft), and is surrounded by a rim that rises 45 m (150 ft) above the surrounding

plains. The center of the crater is filled with 210-240 m (700-800 ft) of rubble lying above

crater bedrock.

The crater was created about 50,000 years ago during the Pleistocene epoch when the local climate on the Colorado Plateau was much cooler and damper. At the time, the area was an open grassland dotted with

woodlands inhabited by woolly mammoths, giant ground sloths, and camels. It was

uninhabited by humans, the first of whom are thought to have reached North America

only around 13,000 years ago.

The object which excavated the crater was a nickel-iron meteorite about 50 meters (54 yards) across, which impacted the plain at a speed of

several kilometers per second. The speed of the impact has been a subject of some debate.

Modelling initially suggested that the meteorite struck at a speed of up to 20 kilometers per

second (45,000 mph), but more recent research suggests the impact was substantially slower, at 12.8 kilometers per second (28,600 mph). It is

believed that about half of the impactor's 300,000 tonne (330,000 short tons) bulk was vaporized during its descent, before it hit the

ground.

Berringer Crater, Arizona

Permian ExtinctionPermian Extinction

80% of species wiped out80% of species wiped out

Cretaceous ExtinctionCretaceous Extinction

50% of species wiped out50% of species wiped out

180 km

LandLand

Continental ShelfContinental Shelf

To Can Cun

3d gravity Anomaly of impact crater

Mars: 2 small, irregular shaped moonsMars: 2 small, irregular shaped moons1. Demos: 8 km long1. Demos: 8 km long

2. Phobos: 27 km long, circles Mars/8hrs and 2. Phobos: 27 km long, circles Mars/8hrs and will crash in 20 mawill crash in 20 ma

Mars Moon: DeimosMars Moon: Deimos

Mars Moon: PhobosMars Moon: Phobos

Jupiters MoonsJupiters Moons

Jupiter (18 moons)Jupiter (18 moons)4 large moons4 large moons

1. Io: very close to Jupiter causing 1. Io: very close to Jupiter causing huge land tides (+90km) causing huge land tides (+90km) causing tremendous internal friction…this heat tremendous internal friction…this heat leads to intense volcanic activity -> leads to intense volcanic activity -> sulphur volcanoessulphur volcanoes

IoIo

IoIo

IoIo

““Gravitational tug of war”Gravitational tug of war”

IoIo

volcanic plumevolcanic plume

2. Europa: 2nd closest moon 2. Europa: 2nd closest moon Large tides also cause internal Large tides also cause internal

friction…enough to melt water…friction…enough to melt water…so…Europa has thick oceans of so…Europa has thick oceans of convecting water covered by ice.convecting water covered by ice.

EuropaEuropa

Europa ice cracksEuropa ice cracks

Ice Ice Oceans Oceans Solid Rocky Mantle ?Solid Rocky Mantle ?Core ?Core ?

3. Ganymede: grooves (ridges and 3. Ganymede: grooves (ridges and valleys) that are younger than craters valleys) that are younger than craters suggesting?? Ice crustal plates??suggesting?? Ice crustal plates??

4. Callistro: most cratered object in 4. Callistro: most cratered object in Solar SystemSolar System

Both largely frozen ice with silicate Both largely frozen ice with silicate rocky cores.rocky cores.

GanymedeGanymede

Largest moon in Largest moon in SSSS

Grooves, ridges of ice?Grooves, ridges of ice?

CallistoCallisto

Saturn (22 moons)Saturn (22 moons)Titan: atmosphere of hydrocarbons Titan: atmosphere of hydrocarbons

and nitrogen; oceans of hydrocarbonsand nitrogen; oceans of hydrocarbons½ rocks and ½ frozen water½ rocks and ½ frozen waterNN22 atmosphere atmosphereLanded there 2 yrs agoLanded there 2 yrs ago

Titan Titan 22ndnd largest moon in SS largest moon in SS

TitanTitan

Titan’s surface

Uranus (15 moons)Uranus (15 moons)SmallSmallMiranda: bizarre V-shaped groovesMiranda: bizarre V-shaped grooves

MirandaMiranda

MirandaMiranda

V-groove: V-groove: Plate Tectonics? Plate Tectonics? Meteorite impact? Meteorite impact?

Shrinkage?Shrinkage?

Neptune (8 moons)Neptune (8 moons)TritonTriton

Largest moon of NeptuneLargest moon of NeptuneVolcanic activity (geysers of carbon-Volcanic activity (geysers of carbon-

rich material of Nrich material of N22))Probably a captured planet (same Probably a captured planet (same

size as Pluto)size as Pluto)

TritonTriton

TritonTriton

Triton’s surfaceTriton’s surface

Nitrogen geyserNitrogen geyser

Nitrogen Nitrogen geysergeyser

Pluto (3 moons)Pluto (3 moons)CharonCharon

½ size of Pluto½ size of Pluto

Eris: 1 moon called DysnomiaEris: 1 moon called Dysnomia

Do WS 20.1Do WS 20.1