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Ch 05--Earth and Moon
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth and Moon
• Will the ozone layer, which is now being depleted,
naturally replenish itself?
• Who was the first person to walk on the Moon and on
what Apollo space mission did this landing occur
• Do we see all parts of the Moon’s surface at some time
throughout the lunar cycle of phases?
• Does the Moon rotate, and if so, how fast?
• What causes the ocean tides?
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth and Moon
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Earth’s Atmosphere
Plate Tectonics
Earth’s Interior
Earth’s Magnetic Field
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Moon’s surface
Humans exploring the moon
Moons origin
Moons causing tides on the earth
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth--Basic Facts
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ASTR103, GMU, Dr. Correll
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Earth: Dynamic and Vital World
• Evolution of the Earth’s atmosphere
– Initially, hydrogen and helium from the solar nebula
• Expelled after few 10’s of millions of years by Sun’s radiation
– 2nd generation, carbon dioxide (CO2), water (H20), and nitrogen
(N2) from volcanic activity of hot, young Earth
• Formation of oceans, from extant water, and from water delivered by
comets, began absorbing CO2
– Evolution of plant life in oceans began processing and
transforming atmosphere--3rd generation
• carbon dioxide a component of seashells--limestone
• over billions of years, massive limestone bedrock form
• plants release oxygen which first caused oxidation of surface (rust!),
but eventually stabilized at present levels
– 4 to 1 mixture of nitrogen to oxygen (with traces of other gases)
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth’s Atmosphere
• Troposphere-lowest level,
where the weather
happens
• Stratosphere-important…where
the ozone (O3)
resides
– Ozone protects us
from the Sun’s
harmful Ultraviolet radiation
28 Sep 2000
• Ozone--created by sunlight and
O2, destroyed by sunlight and
certain industrial age pollutants
ASTR103, GMU, Dr. Correll
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Plate Tectonics
• Continents originally
believed to be adjacent
– Noticed by Newton, of
course
– 1912, Alfred Wegener
proposes continental drift
theory
• “Pangea”
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Plate Tectonics
• Where plates move
apart, we see ridges
– mid-atlantic ridge for
example
• Where plates press
together we have
mountain ranges and
earthquake fault lines
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth’s Interior
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth’s Interior
• During the formation of the Earth energy from
collisional accretion and nuclear fission
(radioactive decay of uranium for example) heat
the Earth led to planetary differentiation
– heavier elements sank to the center (the core)
– lighter elements rose to the surface (the mantle)
• Molten mantle still exists
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth’s Magnetic Field
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Earth’s Magnetic Field
• The Northern Lights-Aurora Borealis
28 Sep 2000
ASTR103, GMU, Dr. Correll
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The Moon--Basic Facts
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Moon’s Surface
• Mostly volcanic in nature,
but no longer active
– basaltic rock
• Craters, mountains, and
planes (mares) formed
due to bombardment of
solar system debris over
billions of years
• Surface covered with a
layer several inches deep
of fine powder (regolith)
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Exploring the Moon
• Apollo 11--first lunar
landing
– Neil Armstrong--first
person on the moon
• Apollo 11-17
– all but one successfully
returned from the moon
with samples (moon
rocks)
– Apollo 13 made a good
movie, though
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Moon’s Interior
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ASTR103, GMU, Dr. Correll
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Origin of the Moon
• Fission theory--moon separated from the
Earth in the early era
• Capture theory--moon formed elsewhere in
the solar system and was captured later in
Earth’s gravity
• Collision ejection theory--moon formed from
debris of collision between Earth and another
body
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Moon’s Origin
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Rotation of the Moon
• Moon rotates
synchronously with the
Earth
– one rotation of the Moon for
one revolution about the
Earth
• Due to tidal forces--Earth’s
gravity stronger on near
side of moon than on far
side
– warping of moon’s molten
mantel when the moon was
young dissipated rotational
energy
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Tides on the Earth
• Moon’s gravity causes Earth’s oceans to oblate (only a few feet).
As the Earth rotates through the bulges, the tides occur. A similar
but weaker effect comes from the sun
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Moon’s orbit growing
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ASTR103, GMU, Dr. Correll
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Earth and Moon
• Will the ozone layer, which is now being depleted,
naturally replenish itself?
– Yes, created naturally by sunlight
• Who was the first person to walk on the Moon and on
what Apollo space mission did this landing occur
– Neil Armstrong, Apollo 11, 1969
• Do we see all parts of the Moon’s surface at some time
throughout the lunar cycle of phases?
– No, synchronous rotation shows us only the near side
• Does the Moon rotate, and if so, how fast?
– Once per revolution about the Earth
• What causes the ocean tides?
– The Moon’s gravitational field oblating the oceans
28 Sep 2000
ASTR103, GMU, Dr. Correll
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Questions for thought
• Describe the formation of the solar system,
specifically address how this lead to the formation
of the inner terrestrial planets and the outer gas
giants. What additional processes happened on
the Earth to create it’s interior, continents, oceans,
and atmosphere.
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ASTR103, GMU, Dr. Correll
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