Origin of the Universe, Solar System and our Planet

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Origin of the Universe, Solar System and our
Planet
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What do you know about the formation of the
Universe?

• When and how did Earth and its moon come into
  being?
• How did the core, mantle, crust form?

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A Quick Overview todays Lecture

• The Big Bang
• Red Shift
• Accretion of Solar System
• Earth
• Moon

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Origin of the Universe

• Provide important information concerning age of
  Earth
• Fragments of larger bodies that have undergone
  collision and broken into pieces

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Origin of the Universe

• Stony meteorites
• Rocky composition
• Iron meteorites
• Metallic composition
• Stony-iron meteorites
• Mixture of rocky and metallic
• Proxy for core composition
• Most date around 4.6 billion years ago

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Origin of the Universe

• Stars cluster in galaxies
• Organized in disks
• Milky Way
• Our galaxy of stars

M100 and NGC1365 are spiral nebulae
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Question 1

• Evidence for the Big Bang Hypothesis includes
• A. Meteorites be dated at 4.6 Ga
• B. A shift towards the Red end of the visible
  light spectrum in different galaxies
• C. The Sun is made of 70 Hydrogen and 27 He

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The Red Shift

• The Red Shift is similar to the Doppler effect
  with sound.
• For objects approaching us, the pitch of the
  sound is skewed to the higher frequency.
• Think of a train approaching and blowing its
  horn.
• Same thing for light waves.

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1912 Slipher - redshifts of spiral nebulae

• Slipher measured spectra from the nebulae,
  showing that many were Doppler-shifted, that is,
  the frequency of light was affected by speed of
  the source (just as the frequency of sound alters
  for a passing train). By 1924, 41 nebulae were
  measured, and 36 of these were found to be
  receding.

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Doppler

• Stars and galaxies emit visible light which can
  be split up into its component colors to form a
  spectrum. Lines appear in this spectrum
  corresponding to the existence of different
  elements in the source of the light. If the
  source were stationary then the lines are in a
  particular pattern, which corresponds to the
  pattern produced by the same elements as are
  emitting light, on the surface of the Earth.

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Doppler

• If the source of light is moving towards the
  Earth then the wavelength of all the emitted
  waves is compressed a little. This results in a
  shift of the spectral lines into the blue part of
  the spectrum, known as a blue shift (middle
  panel). Conversely if the source of the light is
  moving away from the Earth then there is a shift
  of the lines into the red part of the spectrum
  known as a red shift, due to the wavelength of
  the emitted light all being extended a little
  (Bottom panel).

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Red Shift vs Distance

• If the red of light emitted from stars is plotted
  vs their distance from Earth, we see a
  relationship that indicates that the velocity an
  object is moving away from Earth is related to
  its distance

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Origin of the Universe

• Expanding universe
• Galaxies move apart
• Redshift
• Originally concentrated into a single point
• Big Bang
• 15 billion years ago
• Age of universe

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The Big Bang (10-35 seconds) The universe begins
with a cataclysm that generates space and time,
as well as all the matter and energy the universe
will ever hold. For an incomprehensibly small
fraction of a second, the universe is an
infinitely dense, hot fireball. The prevailing
theory describes a peculiar form of energy that
can suddenly push out the fabric of space.
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The Universe Takes Shape (10-6 seconds)After
inflation, one millionth of a second after the
Big Bang, the universe continues to expand but
not nearly so quickly. As it expands, it becomes
less dense and cools. 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.
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Formation of Basic Elements (3 seconds)Protons
and neutrons come together to form the nuclei of
simple elements hydrogen, helium and lithium. It
will take another 300,000 years for electrons to
be captured into orbits around these nuclei to
form stable atoms.
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The Radiation Era (10,000 years)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 take up the faint glow of microwaves which
bathe the entire universe.
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Beginning the Era of Matter Domination (300,000
years)At this moment, the energy in matter and
the energy in radiation are equal. But as the
relentless expansion continues, the waves of
light are stretched to lower and lower energy,
while the matter travels onward largely
unaffected. At about this time, neutral atoms are
formed as electrons link up with hydrogen and
helium nuclei.
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Birth of Stars and Galaxies (300 million years)
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. This point is still
perhaps 12 to 15 billion years before the
present.
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Birth of Stars and Galaxies (300 million years)
The Hubble Space Telescope recently captured
some of the earliest galaxies ever viewed. They
appear as tiny blue dots in the Hubble Deep Field.
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Birth of the Sun (5 Billion Years BP) 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.
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Birth of the Sun (5 Billion Years BP) The image
on the below, 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.
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A Hubble Space Telescope view of a small portion
of the Orion Nebula reveals five young stars.
Four of the stars are surrounded by gas and dust
trapped as the stars formed, but were left in
orbit about the star. These are possibly
protoplanetary disks that might evolve on to
agglomerate planets.
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Origin of the Universe

• The Earth is part of the Solar System the Solar
  System is part of the Milky Way galaxy and the
  Milky Way galaxy is part of the Universe.
• The story of the origin and history of the Earth
  requires that the origin and history of the
  Universe and Solar System must be considered.

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Origin of the Universe

• Evidence to be considered when interpreting the
  history of the Universe
• Galaxies are rapidly moving apart (Hubble's Law).
  Suggests that galaxies were closer together in
  the past. Discovered by Edwin P. Hubble in 1929.
• Observed temperature of the Universe today
  (background microwave radiation) 3 degrees above
  absolute zero.
• Present abundances of hydrogen and helium.

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Origin of the Universe

• Interpretation
• The Universe is expanding.
• Everything began together at a point.
• A big explosion occurred, which astronomers call
  the Big Bang.
• This explosion caused everything in the Universe
  to begin moving rapidly apart.

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How do we know the galaxies are moving apart?

• Red shift.In 1914, W.M. Slipher first noted that
  galaxies displayed the red shift.Their light is
  shifted toward the red (or long wavelength) end
  of the spectrum.
• Colors of the spectrum R O Y   G   B I V

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What the Spectrum Reveals

• The spectrum of a star reveals
• The star's composition by means of absorption
  lines. Various elements in the star's atmosphere
  absorb parts of the light of the spectrum.
• Whether it is moving toward or away from the
  Earth (and at what speed).

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How do we know the galaxies are moving apart?

• Light reaching us from distant receding galaxies
  has its absorption lines shifted toward the red
  end of the spectrum. This indicates that the
  galaxy is moving away from the Earth.
• The red shift indicates that the universe is
  expanding.

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Schematic view of the solar system, showing
orbits of the planets.
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Example of two fusion reactions. (n neutron).
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Origin of the Universe

• Galactic matter is concentrated
• Stars form
• Our Sun
• Supernova
• Exploding star
• Solar nebula
• Dense rotational cloud

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Origin of the Universe

• Galactic matter is concentrated
• Stars form
• Our Sun
• Supernova
• Exploding star
• Solar nebula
• Dense rotational cloud

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Origin of the Solar System

• Rocky debris
• Collided to form aggregates
• Aggregates collided to form asteroids
• 40 km diameter
• Some coalesced to form planets

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Conceptual diagrams of stages in the Earths
early history. (A) Growth of the planet by the
aggregation of particles and meteorites that
accreted and bombarded its surface. At this time,
the Earth was composed of a homogeneous mixture
of materials. (B) The Earth has shrunk because of
gravitational compression. Temperatures in the
interior have reached a level at which
differentiation has begun. Iron (red drops) sinks
toward the interior to form the core, whereas
lighter silicates move upward. (C) The result of
the differentiation of the planet is evident by
the formation of core, mantle, and crust.
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Origin of the Solar System

• Planets formed near time of suns formation
• 4.6 billion years ago
• Planets far from sun are formed from volatile
  elements
• Planets close to sun are rocky

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Sun's energy is the force behind many geologic
processes on Earth

• Evaporation of water to produce clouds, which
  cause precipitation, which causes erosion.
• Uneven heating of the Earth's atmosphere causes
  winds and ocean currents.
• Variations in heat from Sun may trigger
  continental glaciations or change forests to
  deserts.
• Sun and moon influence tides which affect the
  shoreline.

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The Planets

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune
9. Pluto

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The Planets

• Jovian planets
• Large
• Low density (0.7 - 1.5 g/cm3)
• Gaseous
• Jupiter, Saturn, Uranus, Neptune

• Terrestrial planets
• Small
• Dense (4 - 5.5 g/cm3)
• Rocky Metals
• Mercury, Venus, Earth, Mars

Other Small Low density Pluto
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Accretion and Differentiation of the Earth
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Earths Internal Layered Structure

• The Earth is internally layered, with a basic
  structure consisting of
• Crust
• Mantle
• Inner and outer core
• The Earth's internal structure may be primary
  (formed initially as the Earth formed), or
  secondary due to later heating.

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Solar Nebula Hypothesis or Cold Accretion
Model(Secondary Differentiation)

• Earth formed by accretion of dust and larger
  particles of metals and silicates.
• Earth was originally homogeneous throughout - a
  random mixture of space debris.
• Origin of layering requires a process of
  differentiation.
• Differentiation is the result of heating and at
  least partial melting.

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Possible sources of heat for melting

• Accretionary heat from bombardment (meteorite
  impacts)
• Heat from gravitational compression as material
  accumulated
• Radioactive decay

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Differentiation after Accretion

• Iron and nickel sink to form core.
• Less dense material (silicon and oxygen combined
  with remaining iron and other metals) forms
  mantle and lighter crust (dominated by silicon
  and oxygen).
• Presence of volatile gases on Earth indicates
  that complete melting did not occur.
• Earth was repeatedly partly melted by great
  impacts, such as the Moon-forming impact.

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An alternative modelHot Accretion (Primary
Differentiation)

• Internal zonation of planets is a result of hot
  heterogeneous accretion.
• Hot solar nebula (over 1000 oC).
• Initial crystallization of iron-rich materials
  forms planets core.
• With continued cooling, lower density silicate
  materials crystallized.

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Origin of the Solar System

• Cold accretion model - Earth was initially
  unsorted material but now layered. Requires a
  process of differentiation . Heating and at
  least partial melting. Iron and nickel sink to
  form core. Less dense material forms mantle and
  lighter crust. Source(s) of heat for melting?
  Accretionary heat from bombardment Heat from
  gravitational compression Radioactive decay

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Origin of the Solar System

• Hot accretion model - Internal zonation of
  planets is a result of hot heterogeneous
  accretion . Hot solar nebula (over 1000 C).
  Initial crystallization of iron-rich materials
  forms planet cores. With continued cooling,
  lower density silicate materials crystallized.

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Which Model?

• Solar Nebula Hypothesis also known as the
• Cold Accretion Model (secondary differentiation)
• OR
• Hot Accretion Model (primary differentiation)
  ???
• Parts of both models may have been in operation.

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Origin of the Solar System

• Lines of evidence that must be considered
• Planets revolve around sun in same direction -
  CCW
• Planets lie roughly within sun's equatorial plane
  (plane of sun's rotation)

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Origin of the Solar System

• Planets rotate CCW, except for Venus - slowly CW
  Uranus - on its side Pluto - on its side
• Moons go CCW around planets (few exceptions)
• Distribution of densities and compositions
  related to distance from sun
• Age - Moon and meteorites 4.6 by

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Origin of the Solar System

• Hypotheses Solar Nebula Hypothesis or Nebular
  Hypothesis - cold cloud of gas and dust,
  contracts. flattens, and rotates, 90 of mass to
  center condensed, shrank, and heated by
  gravitational compression to form sun. Accretion
  of matter around central mass to form
  protoplanets (cold accretion). Solar wind drove
  lighter elements outward causing observed
  distribution of masses and densities.

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Formation of the Planets

• Solar System Sun - 70 H, 27 He, 3 heavier
  elements Fusion reaction Planets
• Terrestrial Small Dense (4 - 5.5 g/cm3) Rocky
  Metals
• Jovian Large Low density (0.7 - 1.5 g/cm3)
  Gaseous

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Formation of the Moon

• The Moon's low density (3.3 g/cc) shows that it
  does not have a substantial iron, The Earth does.
  
• Moon rocks contain few volatile substances (e.g.
  water) -- implies extra baking relative to Earth.
  
• The relative abundance of oxygen isotopes
  ( 16 O, 17 O, 18 O) on Earth and the Moon are
  identical -- suggests that the Earth and Moon
  formed at the same distance from the Sun.

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Formation of the Moon

• Reasonable theories that don't work
• Co-formation The Moon formed in orbit about the
  Earth via accretion. If the Moon formed in the
  vicinity of the Earth it should have nearly the
  same composition -- specifically a significant
  iron core.
• Capture The Moon's different composition could
  be explained if it formed elsewhere in the Solar
  System and was subsequently captured into Earth
  orbit. Capture into the Moon's present orbit is
  very improbable. Something would have to slow it
  down by just the right amount at just the right
  time.

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Formation of the Moon

• Fission The Moon's composition resembles that of
  the Earth's mantle . A rapidly spinning Earth
  could have cast off the Moon from its outer
  layers. The Earth-Moon system should contain
  fossil evidence of this rapid spin. It does not.
  All of these hypotheses do not address the extra
  baking lunar material has received.

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Formation of the Moon

• Catastrophic Collision An object about the size
  of the planet Mars the Earth, heating and
  ejecting the outer layers of both objects. The
  Moon formed from this ejected material. Explains
  why the Moon is made mostly of rock and why that
  rock was heated excessively. Catastrophic
  collision were common late in the formative
  stages of the solar system. Computer models show
  that a collision at just the speed and angle will
  produce the right amount of debris in Earth
  orbit. Today, this scenario is widely accepted.

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Origin of Earth and Moon

• Moon formed from impact
• Mantle of impacting body
• Proportions of Fe and Mg differ from Earths
  mantle

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Formation of the Moon
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Origin of Earth and Moon

• Earth materials differentiated
• Dense at center
• Less dense silicates rose to surface
• Magma ocean
• Cooled to form crust
• Meteorite impacts increased concentrations of
  some elements in upper Earth

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Origin of Earth and Moon

• Moons maria
• Seas
• Craters formed by asteroids
• Floored by basalts
• Craters
• 3.84.6 billion years old
• Earth also impacted
• Tilted Earth 23.5

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Origin of Earth and Moon

• Heat Flow
• Decreased through time
• Indicates abundant hot spots, small lithospheric
  fragments

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The Hadean

• A time of major changes and Earth formation. No
  rock record.
• Origin of the Earth and solar system
• Differentiation of the Earth to form crust,
  mantle and core
• Cold accretion model, heating from impacts and
  radioactivity lead to molten Earth and
  gravitational differentiation

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The Hadean

• Origin of the atmosphere
• Condensation of water vapor
• Origin of continental crust
• Oldest dated Earth rocks are 3.96 by old (Canada)

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Origin of Earth and Moon

• Earths oceans
• Volcanic emissions cooled, condensed
• Salts
• Carried to sea by rivers and introduced at ridges
• Approximately constant through time

• Early atmosphere
• Differ from the book a little
• Possibly two atmospheres
• 1st was left over H and He
• 2nd Atmosphere
• Degassing from volcanic emissions
• CH4 and NH3 abundant
• Little O2
• No photosynthesis

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Evolution of the Atmosphere

• Atmosphere - Envelope of gases that surrounds the
  Earth. Used by life as a reservoir of chemical
  compounds used in living systems. Atmosphere has
  no outer boundary, just fades into space. Dense
  part of atmosphere (97 of mass) lies within 30
  km of the Earth (so about same thickness as
  continental crust).

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Evolution of the Atmosphere

• Chemical Composition Today -
• Nitrogen (N2)- 78
• Oxygen (O2)- 21
• Carbon Dioxide (CO2) - 0.03
• plus other miscellaneous gases (H2O for one).

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First Atmosphere

• Composition - Probably H2, He
• Fate?
• Blown away during ignition of the sun

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Second Atmosphere

• Produced by volcanic outgassing.
• Gases produced were probably similar to those
  created by modern volcanoes (H2O, CO2, SO2, CO,
  S2, Cl2, N2, H2) and NH3 (ammonia) and CH4
  (methane)
• No free O2 at this time (not found in volcanic
  gases).

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Addition of O2 to the Atmosphere

• Today, the atmosphere is 21 free oxygen. How
  did oxygen reach these levels in the atmosphere?
• Photochemical dissociation - breakup of water
  molecules by ultraviolet
• Produced O2 levels approx. 1-2 current levels
• At these levels O3 (Ozone) can form to shield
  Earth surface from UV
• Photosynthesis -
• CO2 H2O sunlight CH2O O2
• produced by cyanobacteria, and eventually higher
  plants - supplied the rest of O2 to atmosphere.

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The Oceans

• Where did the oceans come from, according to
  modern scientific theories?
• This is one area where there is a lot of
  speculation. Scientists studying oceanic origins
  have come up with three possibilities.

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The Oceans

• The first theory is that the earth has always
  contained the basic elements that make up water -
  hydrogen and oxygen, and that most of the water
  that later formed oceans was trapped separately
  as hydrogen (in hydrocarbons) and oxygen (in iron
  oxides) below the crust. A variation of this
  theory says that liquid water could have
  been trapped in clays. The trapped water was
  released later, as the earth cooled, as steam
  from volcanoes. Once the steam entered the cooler
  atmosphere, it condensed and filled the lower
  basins, which became oceans.

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The Oceans

• The next theory is that the earth collected the
  water over a long period of time as a result of
  ice-bearing comets or meteorites that impacted
  the surface. Some scientists who favor the hot
  accretion model suspect that there could
  not have been enough water at the high
  temperature of early earth to account for all of
  the water present in the oceans of earth.

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The Oceans

• The last theory is a combination of the first
  two. One of the reasons that there has been so
  much interest in studying comets is to measure
  the amount of water contained in them, in hopes
  of validating or disproving the cometary
  hypothesis.

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What was the fate of the first Atmosphere?

• A. Consumed by early life which resulted in mass
  extinction
• B. Absorbed by the Suns gravitational pull
• C. Blown away when the Sun ignited