3 Formation of Earth KD

7/29/2019 3 Formation of Earth KD

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OceanographyGEO 9

Kirk Domke

Winter 2013

Lecture 3:Earth and Water

A Planetary View

Formation of the Universe

Formation of the Solar System

Why the Earth has oceans

Development of Earth's atmosphere

Andromeda Galaxy, 2.5 Million light years away

Universe = everything that physically

exists (matter and energy) Formation of the Universe

The Big Bang

Expanding Universe

redshift

Cosmic Microwave Background

afterglow

Theory + Observation


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Redshift

A doppler effect indicating objects moving away

Frequency of light shifts as the

light propagates through agravitational field

Absorption spectrum of sunlight (left )

vs. light from distant galaxy (right)

Melvin Slipher, 1912

Discovered 12 galaxies beyond the Milky Way all showinga redshift

Mt.Wilson Observatory Edwin Hubble1927 above Pasadena at Mt. Wilson

Adds to Sliphers observations (39 galaxies) to discover acorrelation of the objects distances with their redshiftsmost distant at the greatest velocity


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Edwin Hubble1927 above Pasadena at Mt. Wilson

Adds to Sliphers observations (39 galaxies) to discover a

correlation of the objects distances with their redshifts

The most distant ones have the greatest velocity

Einstein 1917, Theory of

General Relativity

The basis of models of aconsistently expanding

universe

Problem section omitted

Einstein vs. de Sitter

William de Sitter 1917

Finds a solution to Einsteins

model

Discovers a positivecosmological constant, resulting inan exponentially expanding,empty universe

Einstein vs. de Sitter Exponentially expanding universe


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Cosmic Microwave BackgroundThe space between stars and galaxies (the background) iscompletely dark, right?

Wrong. A decent radio telescope can detect a faint

background glow.

This glow is uniform and not associated with any star,galaxy, or other object.

Arno Penzias and Robert WilsonIn 1964, discovered this glow is strongest in themicrowave region of the radio spectrum.

Earned the 1978

Nobel Prize.

CMB and COBE MissionCMB glow data points on the theoretical curve for auniverse that used to be really hot everywhere.

The data points FIT PERFECTLY, with error bars too small

to draw on the graph!

It's one of the most triumphant scientific results in history.

George Smoot and John Mather, received the Nobel Prizein Physics in 2006 for their work on the project.


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Timeline from the Big Bang to the Formation of

Our Universe

13.75 billion years ago

Origin of the universeA point source of mass/energy

Recombination - the first 380,000 years

An expanding hot (~108 C) opaque/foggyfluid of atom parts

There is light, but not observable

CMB dates from this time

Big Bang Timeline

Reionization after first 150 million years

Masses locally condense to form stars

There is light! Reionizes rest of universe, made of plasma

Big Bang Timeline

Reionization after first 150 million years

Masses locally condense to form stars

There is light! Reionizes rest of universe, made of plasma

There was no light between recombinationand reionization

Dark Ages

Big Bang Timeline


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First Galaxies 650 million yrs ABB

Found just last year! Hubble Ultra Deep Field images

Big Bang TimelineUDFy-38135539

Galaxies, Stars, Nebulae


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A huge rotating aggregation of stars, dust, gas

and other debris

Stars and planets are contained within galaxies

Stars are massive spheres of hot glowing gases

Stars convert hydrogen (H) and helium (He) toheavier elements by nuclear fusion as they age

(nucleosynthesis)

GalaxiesMilky Way

Milky Way GalaxyMilky Way Galaxy

Large spiral galaxy

Rotation around the galactic nucleus

Outermost stars move the slowest

Sun rotates around the galactic nucleusonce about every 200 million years


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The Solar System

Solar System is 8.4 billion years old

Condensed from a cloud of gas and dust,

including remnants of older exploded stars

(Supernovae)

Origin of a Solar System

The Nebular Model

Nebular cloud Nebula of gas and dust

GASES (~98.6%)

Hydrogen , Helium

ICES (~1.1%) (80%)

Water, Methane, Ammonia

ROCKS (~0.22%) (15%)

Silicates, Oxides

METALS (~0.08%) (5%)

Iron, Nickel


The Nebular Model

Nebula contracts under

gravity

Heats up

Flattens out Spins faster

Gravitational attraction


The Nebular Model

99.9% of mass collapsed to

form sun with 0.1% in the

remaining mass (gas anddust) in the rotation planecontracted to form

planetismals

Hydrogen and helium

remain as gases

Star formation


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The Nebular Model

The planets build up byaccretion and collision by

gravitational attraction,

accompanied by a great

increase in temp and

pressure

Planetary formation

The strong thermal and pressure gradient developed by the earlysun evaporated the volatile elements in the inner (terrestrial)planets and condensed them in the colder outer (gaseous)planets.

The chemistry of the planets is related to their distance from thesun.

Configuration of Planets

Planetary Processes

AccretionGrowth vs Fragmentation

HeatingAccretionary and Radioactive Heat

MeltingSphericity + Differentiation (density)

Atmosphere AcquisitionPRIMARY ATMOSPHERES

H (hydrogen) + He (Helium) from Pre-Solar Nebula

SECONDARY ATMOSPHERES

Accumulate after Nebula has dispersed

Gas from Comet Ice H2O, CO2, CO, CH4, NH3, etc.

Erupting Volcanoes H20, CO2, N2, H2S, SO2, etc.

Heavy Molecules held by Gravity of Planets >0.1 Earth Mass

Planetary Processes












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Planetary Processes











GAS= Low DensityICE = 1 gm/cc

ROCK = 3 gm/ccMETAL = 7 gm/cc

1

3

7


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LOSS OF GAS TO SPACE

PHOTODISSOCIATION UV light

H2 He CH4 NH3 H2O N2 CO22 4 16 17 18 28 44

Molecular

Weight

2H2O 2H2 + O2

CH4 2H2 + C

2NH3 3H2 + N2

CO2

UV

UV

UV

Volatiles from mantle or from comets

enriched

PrimaryAtmospheres:

H + He from Nebula

Secondary

Atmospheres:

Comets + Volcanoes addH2O, CO2, CH4, NH3, SO2

and other gases

(in addition to CO2 + N2left behind)

H2O = water,

CO2 = carbon dioxide,

CH4 = methane,

NH3 = ammonia,

SO2 = sulfur dioxide

Cool Surface isneeded !

Hot, molten surface

drives gases into

space

Solar Radiation decreases with distance from Sun

Inverse Square Rule:Heat depends on (1/ Distance2)

(Venus) 1 / (0.72)2 = 1.93

(Mercury) 1 / (0.4)2 = 6.25

Earth 1 AU


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Modern atmopsheric composition

High P (90 atm) Low P (0.007 atm)P = 1 atm

VENUS:Large Rocky

Planet

VENUS(Hell Planet)

Very Thick, Cloudy Atmosphere (90 atm)

Extremely High, Invariant Temp. 850o F

Russian

Venera Lander

Photos

Atmosphere Pressure:0.007 bar (MARS) LOW!

Earth = 1 bar = 1 atmosphere

Atmosphere Composition: CO2 + N2 (Like Venus)

Atmosphere Origin: Secondary (Comet, Volcano)

But Mars gravity is too low to hold all gases

MARS

MARS is only size and 1/10th mass of EARTHProbably had liquid water in its early history

BUT now a cold place (mean -60oC)

/ /


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CONDENSATION

H2O vapor H2O liquid

Rain

Mars is cooler than Earth or

Venus


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Ancient sediments on Mars?3.0-4.0 billion years old

(liquid water still around)

2004 image from NASAs Opportunity rover Earth

Water vapor was an original component ofthe Earth

Outgassing of lightest fraction (water, carbon

dioxide, other gases)

Ocean Formation

Alternative suggestion:

Icy comets hit Earth

Ocean Formation

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CONDENSATION

H2O vapor H2O liquid

Rain


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Timeline in billions of years

100

Methane, ammonia

75

Atmosphereunknown

50 Nitrogen

Water

ConcentrationofAtm

ospheric

Gases(%)

25

Carbon dioxide Oxygen

04.5 4 3 2 1

Time (billions of years ago)

Transitions less well known

Time before Present (Ga)

PO2(atm)

1

0.1

0.01

0.001

0.0001

0.00001

4.5 4 3.5 3 2.5 2 1.5 1 0.5 0

Multicellular

algae

Humans

Single-celled microbial

World

First

oxygenic

photosynthetic

algae and

cyanobacteria

First Invertebrate

animals

Lifes History on Earth

?

first cellular life

single-celled

microbesWhy is Earth a suitable planet for sustaining life?

Suitable distance from Sun in the Habitable Zone (not too near/far)

liquid water exists- perfect solvent for carbon biochemistry

locks up CO2 as carbonate minerals.

NASA Astrobiology: Follow the liquid water

Sufficient planetary mass (gravitational pull) to retain an atmosphere

Plate tectonics

get ocean basins and continents, and recycles nutrients

Stabilizing effect of the Moon

lunar tides

seasons

stabilizes tilt of the Earth

To support complex multicellular life, need atmospheric O2

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Early Archean (3.3-3.5 billion yr) Microfossils from Warrawoona Group, Australia.

Cellularly preserved filamentous and colonial fossil microorganisms?

Tiny filaments 1-20 microns in thin section (1 microns = 1/millionth of a meter)

Some fossil evidence for early life

ALSO Interpreted by others as simply mineral crystals

Stromatolite reef from the

Early Archaean era of Australia

Scale bar = 1 cm

All other scale bars = 5 cm

3.43 Ga = 3430 Ma

Laminated rock structures of

possible biogenic origin (7 types)

The Future of our Solar System?

Sun has a lifetime of 5 billion years beforeHYDROGEN fuel runs out and it begins to die!

Forms a RED GIANT phase & engulfs the inner planets

Earth will be obliterated and atoms recycled into space

A challenge for future generations, maybe (if we survive):

i) Overpopulation / dwindling resources

ii) Dramatic climate change

3 Formation of Earth KD

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