Origin of Solar System &
Earth
Chapter 2
What does this have to do with
oceanography?
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Where does water come from?
Why do we have oceans?
Why do we have life as we know it?
Elemental composition
Present day configuration relative to origins
Hydrological cycle
Dissolved gases/Ocean and Atmosphere
Time
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Importance of time scales
Forces at work in the past
Forces at work today
How can we measure age of the earth
How old is Earth?
 Biblical scholars of 19th century (Bishop Ussher) –
6000 years (started at 4004 BC)
 Classical Greeks – infinite – history endlessly
repeats itself
 Mayans believed earth recycled on a 3000 year
time scale
 Han Chinese thought earth was recreated every
23,639,040 years
 The age we now except may change but is
consistent with current theory
More recent efforts
 Lord Kelvin - 80 million years old – based on
cooling of molten Earth
 Darwin - really old based on time for natural
selection (biological argument)
 Hutton – really old based on
uniformitarianism (processes in the past
taking place at rates comparable to today)
(geological argument)
Earth’s age
 Earth is about 4.5 (or 4.6) BY old
 First 700 MY Earth was a spinning cloud of
gas, dust and planetoids
 These condensed and settled to solidify into
a series of planets
 Since that time, geological history and
evolution commenced.
The Big Bang Theory
 Currently the dominant theory
 First iteration proposed by Georges Lemaître in
1927. He observed the red shift in distant nebulas
and invoked relativity.
 Hubble found experimental evidence (1929) –
galaxies are moving away from us with speeds
proportional to their distance.
 Theory suggested because it explains the
expansion & predicts the existence of cosmic
radiation (leftover photons) & nucleosynthesis
 1964 cosmic radiation discovered (Arno Penzias &
Robert Wilson who won the Nobel Prize)
Big Bang – what is it?
 All mass and energy concentrated at a geometric
point
 ~14 or 15 BY ago
 Beginning of space and time
 Expansion/cooling of universe began
 Protons and neutrons form
 Cooling initiated the formation of atoms
(nucleosynthesis) – first mostly H (the most
abundant form of matter in the universe)
Formation of galaxy and stars
 Galaxy – rotating aggregation of stars, dust, gas
and debris held together by gravity
 Stars are massive spheres of incandescent gases
 100’s of billions of galaxies in the universe and
100’s of billions of stars in the galaxies
 Sun is a star
 Sun plus its family of planets is our solar system
 Our solar system formed about 5 BY ago
 Our galaxy is out in a spiral arm
 Our solar system orbits the galaxy’s core
– (230 million year orbit at 280 km/s)
Stars
 Stars form in nebulae, large diffuse clouds of dust
and gas.
 Condensation theory – spinning nebula starts to
shrink and heat under its own gravity
 Protostar – condensed gases
 At temperature of ~10 million degrees C, nuclear
fusion begins (H’s fuse to form He) which releases
energy and stops shrinkage
 Star is stable once fusion reactions begin (form
atoms as heavy as C and O)
Beginning of the end
 Star starts consuming heavier atoms
increasing energy output and swelling to a
“red giant”
 Incinerates planet and throws off matter
including heavy elements
 More massive stars get hotter and consume
H at higher rates and make heavier atoms
(e.g., Fe)
The end
 H is consumed
 Core collapses on itself
 Internal temperatures sore so can no longer
contract
 Cataclysmic expansion called a supernova (30
sec)
 Mass is accelerated outward
 Forces holding apart atomic nuclei are overcome
 Heavier atoms formed
Our Solar System
 Our solar nebula was struck by a supernova
 Caused our condensing nebula to spin
 Introduced heavy atoms to seed the formation of
planets
 5 BY ago, the solar nebula was 75% H, 23% He
and 2% other material
 Center became protosun
 Outer material became planets – smaller bodies
that orbit a star but do not shine by their own light
Planets
 Grew by accretion – big clumps use gravitational pull to accrete
condensing matter
 Near sun, first materials to solidify had higher boiling points (metals
and rocky minerals) – Mercury is mostly Fe, Ni. Inner rocky planets.
 Next Mg, Si, H2O and O2 condensed (plus some Fe and Ni). Middle
planets (e.g., Earth).
 CH4 and NH3 in frigid outer zones. Outer gassy planets (Jupiter,
Saturn, Uranus and Neptune).
Stabilization of solar system
 Protosun became star (sun) and nuclear fusion
began
 Solar wind (radiation) at the start of those
reactions cleared excess particles and ended
rapid accretion of inner planets.
Early Earth
 Homogeneous throughout during initial accretion of cold particles
 Surface heated by impacts (asteroids, comets and debris)
 Heat, gravitational compression, radioactive decay caused partial melting.
 Density stratification.
Gravity pulled heavy
elements to interior.
 Friction during this
produced more heat.
 Lighter minerals (Si,
Mg, Al and O-bonded
compounds) migrated to
surface forming Earth’s
crust.
Later
 Earth began to cool (first surface 4.6 BY
ago)
 Impact of planetary body (4.5 BY ago –
metallic core fell into earth’s core and rocky
mantle was ejected, condensed and formed
our moon.
 New atmosphere formed by outgassing
 Hot vapor condensed to clouds (water)
 Comet impacts added additional water
Formation of liquid water
 Outgassing & cooling to form boiling rain (20
million years)
 Additional cooling – water collected in basins
 Water plus CO2 made carbonic acid which
dissolved rocks (contributed salts)
 More water from comets (~ meters in diameter)
 Carbonaceous chondrites?
 Later, addition of O2 caused oxidation reactions.
 Most of the ocean in place by 4 BY ago
– (new water is 0.1 km3/yr)
– Unclear whether there were always continents
Gases expelled (outgassed)
from volcanos formed new
Earth atmosphere.
•Composed mostly of CO2
and water vapor.
•Clouds reflected about 60%
of sunlight.
•Clouds trapped lots of
energy as well.
Water began accumulating
in liquid form about 4.0 BYA
forming earliest terrestrial
oceans.
Widespread volcanic activity released H2 and smaller quantities of CO2, Cl2, N2 and
H2 which produced a water vapor atmosphere that also contained carbon dioxide
(CO2), methane (CH4) and ammonia (NH3).
As Earth cooled, the water vapor (1) condensed and (2) fell to Earth's surface. There
it accumulated to (3) form the oceans.
Volume of Earth's mantle is 1027
cm3 (ave. density of 4.5 g/cm3).
Total mass for mantle is 4.5 X 1027
g.
Water of oceans has mass of 1.4 X
1024 g.
Mantle lost 0.031% of mass as
water to have produced oceans.
Water from comets
-measure about 9 m (30 ft) in diameter.
-enter atmosphere at rate of about
20/second.
At the observed rate of occurrence, Earth
would receive 0.0025 mm of water per year.
Four billion years of such bombardment
would give enough water to fill the oceans
to their present volume.
Recorded by ultraviolet photometer aboard the satellite Dynamic Explorer 1.
The dark spot or 'hole', thought to be caused by the vaporization of cometlike
balls of ice, is shown in the inset. The dark holes in the atmosphere were 48 km
across and existed for up to 3 minutes. Because of the absorption spectra of
these dark spots, they can be explained only by the comet-like balls of ice
breaking up and vaporizing 1600-3200 km above Earths surface.
Current Ocean Statistics
 97.5 % of water on earth is in the ocean
 2.5 % of water is on land (primarily as ice)
 0.01% is surface
and atm water!
More stats
 Total area of oceans now is 71% of Earth’s
surface
 Avg depth is 3800 m
 Mean sphere depth is 2430 m
– depth at which amount of surface above and
below that depth are equal
 Avg temperature is 4oC (= 39oF; cold)
 Volume 1.4 billion km3
Early Atmosphere
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4.5 to 3.5 BY ago. Rich in CO2, N2, H2O and some CH4 and NH3.
3.5 BY ago began shift toward today’s atmosphere (mostly O2 and CO2)
Chemical weathering: CO2 dissolves in SW to make carbonic acid (acid
dissolved rocks releasing minerals) & photochemical reactions with
atmospheric H2O
 About 2 BY ago, get
introduction of O2 into
atmosphere (after
oxidation reactions).
 Current atm
- 21% O2
- 78% N2
- 0.04% CO2
~0.9% Argon
Origin of Life
 ~ 3.5 BY ago
 Definition – self-replication?
– Capable of growing more complex; obtains energy by
breaking down chemical compounds
 Water is ideal medium for life (retains heat,
moderates temperature, dissolves chemicals,
transports nutrients)
 Source of building blocks
– Primordial soup (mixture of H2Ovapor, NH3, CH4 and H)
– Extraterrestrial – meteorites & comets
 Carbonaceous chondrites have C in the form of organic
compounds including amino acids
Becoming an organism
 Need building blocks plus energy
 Surface pools – biosynthesis
– Concentration of organic matter on surfaces of
clay minerals or bubbles; energy from sunlight
 Deep ocean
– Geothermal energy supplied by hydrothermal
vents and H2S
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Oldest known fossil (3.5 BY) from NW Australia
Life altered the atmosphere
First bacteria – anaerobic
Green algae – evolved from
cyanobacteria
– Photosynthesis
uses CO2 and
evolves O2
 Stromatolites –
clusters of algae
Oscillatoria today
First fossil life – bacteria-like forms (>3.8
BY ago).
•Earliest forms were heterotrophs
(organic compounds).
•Autotrophs eventually evolved
(Oxidized inorganic compounds
through chemosynthesis).
Fossil algae 2 billion years old (left) and living algae
(right). Note the similarities in appearance.
Interspersed among the living algae are chains of rodshaped bacteria.
Photosynthesis:
6H2O + 6CO2 + Sunlight <---> C6H12O6 + 6O2
Two billion year old fossilized stromatolites
from the shores of Great Slave Lake,
North-West Territories, Canada.
Fate of early atmosphere
 Green plants produced O2 and removed
CO2
 C from air became locked up in sedimentary
rocks and dissolved into the oceans
 NH3 and CH4 reacted with atmospheric O2
 N2 was released from reactions of NH3 with
O2 and from denitrifying bacteria.
 O2 built up forming ozone (filtering out UV
rays and allowing more evolution)
Timeline (since big bang)
 10-35 sec ABB (The Big Bang)
– The universe is an infinitely dense, hot fireball.
 10-6 sec ABB (1 millionth of a second)
– Universe forms: Expansion slows down; universe cools
and becomes less dense
– The most basic forces in nature become distinct: first
gravity, then the strong force, which holds nuclei of
atoms together, followed by the weak and
electromagnetic forces. By the first second, the universe
is made up of fundamental particles and energy: quarks,
electrons, photons, neutrinos and less familiar types.
These particles smash together to form protons and
neutrons.
 3 sec ABB
– Formation of basic elements
– Protons and neutrons come together to form the nuclei
of simple elements: hydrogen (1 proton), helium (2
protons) and lithium (3 protons) (1, 2 and 3 in periodic
table). It will take another 300,000 years for electrons to
be captured into orbits around these nuclei to form
stable atoms.
 10,000 yr ABB
– Radiation Era
– The first major era in the history of the universe is one in
which most of the energy is in the form of radiation -different wavelengths of light, X rays, radio waves and
ultraviolet rays. This energy is the remnant of the
primordial fireball, and as the universe expands, the
waves of radiation are stretched and diluted until today,
they make up the faint glow of microwaves which bathe
the entire universe.
 300,000 yr ABB
– Matter dominates
– The energy in matter and the energy in radiation are
equal. As universe expands, waves of light are stretched
to lower and lower energy, while the matter travels
onward largely unaffected. Neutral atoms are formed as
electrons link up with hydrogen and helium nuclei.
Microwave background radiation gives us a direct
picture of how matter was distributed at this early time.
 300 MY ABB
– Birth of stars and galaxies.
– Gravity amplifies slight irregularities in the density of the
primordial gas. Even as the universe continues to
expand rapidly, pockets of gas become more and more
dense. Stars ignite within these pockets, and groups of
stars become the earliest galaxies. (Still perhaps 12 to
15 billion years before the present).
 5 BY ago Birth of the Sun
– The sun forms within a cloud of gas in a spiral arm of the Milky Way
Galaxy. A vast disk of gas and debris that swirls around this new star
gives birth to planets, moons, and asteroids . Earth is the third planet
out.
– The image on the left, from the Hubble Space Telescope, shows a
newborn star in the Orion Nebula surrounded by a disk of dust and
gas that may one day collapse into planets, moons and asteroids.
 3.8 BY ago Earliest Life
– The Earth has cooled and an atmosphere develops. Microscopic
living cells, neither plants nor animals, begin to evolve and flourish
in earth's many volcanic environments.
 700 MY ago Primitive Animals appear
– These are mostly flatworms, jellyfish and algae. By 570 million
years before the present, large numbers of creatures with hard
shells suddenly appear.
 200 MY ago Mammals appear
– The first mammals evolved from a class of reptiles that evolved
mammalian traits, such as a segmented jaw and a series of bones
that make up the inner ear.
 65 MY ago Dinosaurs become extinct
– An asteroid or comet slams into the northern part of the Yucatan Peninsula
in Mexico. This world-wide cataclysm brings to an end the long age of the
dinosaurs, and allows mammals to diversify and expand their ranges.
 600,000 yr ago Homo sapiens evolve
– Our earliest ancestors evolve in Africa from a line of creatures that
descended from apes.
 170,000 yr ago Supernova 1987a explodes
– A star explodes in a dwarf galaxy known as the Large Magellanic
Cloud that lies just beyond the Milky Way. The star, known in modern
times as Sanduleak 69-202, is a blue supergiant 25 times more
massive than our Sun. Such explosions distribute all the common
elements such as Oxygen, Carbon, Nitrogen, Calcium and Iron into
interstellar space where they enrich clouds of Hydrogen and Helium
that are about to form new stars. They also create the heavier
elements (such as gold, silver, lead, and uranium) and distribute
these as well. Their remnants generate the cosmic rays which lead to
mutation and evolution in living cells. These supernovae, then, are
key to the evolution of the Universe and to life itself.
 1054 Crab Supernova appears
– A new star in the constellation Taurus outshines Venus. Chinese,
Japanese, and Native American observers record the appearance
of a supernova. It is not, however, recorded in Europe, most likely
as a consequence of lack of study of nature during the Dark Ages.
The remnants of this explosion are visible today as the Crab
Nebula. Within the nebula, astronomers have found a pulsar, the
ultra-dense remains of a star that blew up.
 1609 Galileo builds first telescope
– Five years after the appearance of the great supernova of 1604,
Galileo builds his first telescope. He sees the moons of Jupiter,
Saturn's rings, the phases of Venus, and the stars in the Milky Way.
 1665 Newton describes gravity
 At the age of 23, young Isaac Newton realizes that
gravitational force accounts for falling bodies on earth as well
as the motion of the moon and the planets in orbit. This is a
revolutionary step in the history of thought, as it extends the
influence of earthly behavior to the realm of the heavens. One
set of laws, discovered and tested on our planet, will be seen
to govern the entire universe.
 1905 Einstein’s Theory of Relativity
Relativity recognizes the speed of light as the
absolute speed limit in the universe and, as such,
unites the previously separate concepts of space
and time into a unified spacetime. Eleven years
later, his General Theory of Relativity replaces
Newton's model of gravity with one in which the
gravitational force is interpreted as the response
of bodies to distortions in spacetime which matter
itself creates. Predictions of black holes and an
expanding Universe are immediate
consequences of this revolutionary theory which
remains unchallenged today as our description of
the cosmos.
 1929 Hubble discovers universe is expanding
– Edwin Hubble discovers that the universe is expanding. The
astronomer Edwin Hubble uses the new 100-inch telescope on Mt.
Wilson in Southern California to discover that the farther away a
galaxy is, the more its light is shifted to the red. And the redder a
galaxy's light, the faster it is moving away from us. By describing this
"Doppler shift," Hubble proves that the universe is not static, but is
expanding in all directions. He also discovers that galaxies are much
further away than anyone had thought.
 1960 Quasars discovered
– Allan Sandage and Thomas Matthews find sources of intense radio
energy, calling them Quasi Stellar Radio Sources. Four years later,
Maarten Schmidt would discover that these sources lie at the edge
of the visible universe. In recent years, astronomers have realized
that they are gigantic black holes at the centers of young galaxies
into which matter is heated to high temperatures and glows brightly
as it rushes in.
 1964 Microwave radiation discovered
– Scientists at the Bell Telephone Laboratories discovered microwave
radiation that bathes the earth from all directions in space. This
radiation is the afterglow of the Big Bang.
 1967 Discovery of Pulsars
– A graduate student, Jocelyn Bell, and her professor,
Anthony Hewish, discover intense pulsating sources of
radio energy, known as pulsars. Pulsars were the first
known examples of neutron stars, extremely dense
objects that form in the wake of some supernovae. The
crab pulsar, is the remnant of the bright supernova
recorded by Native Americans and cultures around the
world in the year 1054 A.D.
 1987 Light from supernova 1987 reaches Earth
– The light from this supernova reaches earth, 170,000
years after is parent star exploded. Underground
sensors in the United States and Japan first detect a
wave of subatomic particles known as neutrinos from
the explosion. Astronomers rush to telescopes in the
southern hemisphere to study the progress of the
explosion and perfect models describing the violent
deaths of large stars.
 1990 Hubble launched
– The twelve-ton telescope, equipped with a 94-inch
mirror, is sent into orbit by astronauts aboard the space
shuttle Discovery. Within two months, a flaw in its mirror
is discovered, placing in jeopardy the largest investment
ever in astronomy.
 1990 Big Bang confirmed
– Astronomers use the new Cosmic Background Explorer
satellite (COBE) to take a detailed spectrum of the
microwave background radiation. These studies showed
that the radiation is in nearly perfect agreement with the
Big Bang theory. Two years later, scientists used the
same instrument to discover minute variations in the
background radiation: the earliest known evidence of
structure in the universe.
 1993 Hubble optics repaired
– Hubble's greatest legacy so far: detailed images of
galaxies near the limits of the visible universe.
 100 Trillion
Future
– Astronomers assume that the universe will gradually
wither away, provided it keeps on expanding and does
not recollapse under the pull of its own gravity. During
the Stelliferous Era, from 10,000 years to 100 trillion
years after the Big Bang, most of the energy generated
by the universe is in the form of stars burning hydrogen
and other elements in their cores.
 1037 yrs
– Most of the mass that we can currently see in the
universe is locked up in degenerate stars, those that
have blown up and collapsed into black holes and
neutron stars, or have withered into white dwarfs.
Energy in this era is generated through proton decay
and particle annihilation.
 1038 to 10100 The Black Hole Era
– After the epoch of proton decay, the only stellar-like
objects remaining are black holes of widely disparate
masses, which are actively evaporating during this era.
 10100 Dark Era Begins
– At this late time, protons have decayed and black holes
have evaporated.Only the waste products from these
processes remain: mostly photons of colossal
wavelength, neutrinos, electrons, and positrons. For all
intents and purposes, the universe as we know it has
dissipated.
From: PBS Online
(http://www.pbs.org/deepspace/timeline/)
Aging the Earth & Solar System
 Dating meteorites, chunks of rock and metal,
formed about the same time as the sun and
planets and from the same cloud.
– Carbonaceous chondrites are a class of meteorites
believed to be the most primitive in the solar system
(silicate minerals, water and carbon)
 Dating moon rocks and oldest rocks found on
Earth (about 3.8 BY old)
 Rate of expansion (2002, astronomers had very
accurate measurements and calculated
backwards to an age of 13-14 BY old).
How do we age things?
 Isotopic decay
 Radioisotopes are unstable and decay to form
daughter products which form next to parent
nuclide.
 Know the ratio of daughter to parent in
undisturbed sample and the rate of conversion
(e.g., decay rate or half-life) allows computation of
age
 This has been done with several isotope pairs to
arrive at age of solar system
Isotopes
 The ordinary isotope of hydrogen, H, is known as Protium, the other
two isotopes are Deuterium (a proton and a neutron; stable) and
Tritium (a protron and two neutrons; unstable). Hydrogen is the only
element whose isotopes have been given different names.
 Radioactive decay – spontaneous disintegration of unstable nuclei
 For low atomic number elements stable is about 1:1 neutrons:protons
in the nuclei. For higher atomic number elements, the ratio is about
1.6:1.
 Heavy nuclides (atomic number > 82) have no stable configuration.
 Different types of decay
 FYI: Fusion of hydrogen into helium provides the energy of the
hydrogen bomb
Some isotopes
Parent isotope
Daughter Isotope
Half Life
238U
235U
232Th
87Rb
40K
39Ar
14C
147Sm
206Pb
207Pb
208Pb
87Sr
40Ar
39K
14N
147Nd
4.47 x 109 years
7.04 x 108 yrs
1.40 x 1010 yrs
4.88 x 1010 yrs
1.25 x 109 yrs
269 yrs
5,730 yrs
1.06 x 1011 yrs
*daughters are smaller and contain fewer protons, neutrons & electrons
Doppler shifting
 Wavelengths emitted by objects moving away are
shifted to lower frequency (towards reds)
 Wavelengths emitted by objects moving towards
us are shifted to higher frequency.
 Example of sound – pitch of fire engine is higher
as truck moves towards you and lower as it moves
away)
 For galaxies outside our group, the redshift is
known as hubble expansion (after Edwin Hubble
who discovered this phenomenon in 1929).
Another way to look at time
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0-7 No record (no baby pics)
8-12 First rocks formed that are preserved today
12 First living cell appeared
22-23 Oxygen appeared
31
Atmosphere becomes oxygenated
40
First fossils formed (earlier records are dubious)
41
First vertebrates
41.7 First land plants
43
First reptiles
45
First flowering plants
45.6 Mammals, birds, insects became dominant
25 days ago First human ancestors
0.5 hours ago Civilization began
1 min ago Industrial revolution began
Geologic Time – Appendix II
Emerging field
 Exobiology
– Carbonaceous chondrites
– Primordial soup
– Reducing environments
– polymerization
 Composition of a cell
–
–
–
–
–
59% H
24% O
11% C
4% N
2% Others (P, S, etc)
 Composition of a cell
–
–
–
–
–
50% protein
15% nucleic acid
15% carbohydrates
10% lipids
10% other
Take home points
 Earth is ~4.5 BY old
 Big bang – expansion and formation of stars/planets from
nebulae
 How starts and planets form – condensation theory
 Origin and formation of atoms
 Changes in the early atmosphere – how it formed, how it
changed and main causes for that change
 Oxygen in the atmosphere
 Origin of water (planetary outgassing, comets, meteorites)
 Sources of heat in the early earth – is the earth heating or
cooling?
 Dating the earth – how do we do it? What do we date?
 Early ocean acidic because of high concentration of carbon
dioxide
Take home (cont)
 Life originated ~ 3.8 BY ago
– Sources of building blocks and energy for life
– Early environments
 Where is the water on earth (reservoirs)
 Building blocks for life – where do the C compounds and
energy come from
 Miller-Urey experiments (synthesis of organic compounds
from chemical soup and energy)