Unit 2: Space

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Unit 2 Space
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Unit 2 Space Overview
Earths Moon The Sun and the Solar System The
Planets and the Solar System Stars and Galaxies
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Earths MoonChapter 25 Theories of the Moon
Formation
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1. Fission
Formation Hypothesis The fast spinning, molten
Earth lost some material, that was flung into
space and formed our moon.
Verdict Fission was disproved because the moon
lacks iron, a common element found on Earth.
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2. Co-Formation
Formation Hypothesis The moon and Earth formed
at about the same time from the debris orbiting
the sun.
Verdict Orbital energy analysis illustrated that
they could not have formed this way.
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3. Capture
Formation Hypothesis The moon was a rogue
celestial body that was cpatured by the Earths
gravitational field.
Verdict Capture was disproved because lunar
rocks were found to have the same isotope
composition as terrestrial (Earth) rocks.
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4. Impact
Formation Hypothesis During the Earths early
formation a planet sized object struck it. The
impact destroyed the object and released debris
into space which eventually coalesced into the
moon we see today.
Verdict This theroy is currently accepted as the
most plausible explanation for the moons
formation.
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Homework
Read Chapter 25, pages 556-557 Make detailed
notes, including diagrams, detailing the impact
formation hypothesis.
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Origin of the Moon

• 4.5 billion years ago the earth is coalescing
  from dust orbiting the sun
• a planet sized object collides with early
  Earth impact hypothesis simulation
• ejected matter orbiting the Earth coalesces
• 4.5 - 4.0 billion years ago the Earth and Moon
  continue to grow in size and mass from continued
  meteoroid bombardment
• frequent impacts melt the surface, forming magma
  oceans
• once the surface cooled and hardened additional
  impacts gouged out craters and raised mountains

Moon Formation Timeline
4.5 BillionYearsAgo 4.0
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Origin of the Moon

• the largest of these later impacts carved out
  great basins and cracked the surface enough for
  lava to flow from the Moons interior
• over the last 3 billion years the Moons
  interior has been geologically inactive
• impacts, although much less frequent, have
  continued, to change the lunar surface creating
  smaller craters
• bombardment continues today, mainly from
  micrometeoroids - tiny objects the size of sand
  grains

Moon Formation Timeline Continued
3.0 BillionYearsAgo Today
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The Moons Appearance
Far Side
The face we see has fewer large craters and far
greater areas of smooth, dark, frozen lava.
Nobody really knows why. - - -
Berman
I was amazed at the apparent lack of scientific
knowledge and common sense in Bermans article
Duh! It doesnt take an astronomer to know that
the same side of the moon always faces the Earth.
Since Earth does not through off comets and
astroids, it stands to reason that the side of
the moon facing Earth would be protected by
Earths mass from asteroid and comet impacts more
than the side facing away from Earth. - -
- Taylor
Worlds Out of Balance
Near Side
_ _ _ _ _ _ _ _ _ Images Sky Lights by Bob
Berman Discover Magazine, December 2003
http//www.discover.com/issues/dec-03/departments/
sky-lights/
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The Moons Appearance
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The Moons Appearance
The Editors Respond
One of the most crucial aspects of the scientific
method is testing a theory against evidence. With
that in mind, lets look at your theory that the
lunar near side is protected from bombardment by
Earths bulk. How much of a solid angle of the
sky does the Earth block as seen from the moon?
The apparent diameter of the Earth is two
degrees. That is about 1/7000 of the Earth-facing
half of the sky -- hardly enough to explain a
significant difference in cratering. In fact,
Earths gravity might act as a slight
gravitational magnifier, causing more meteorites
to strike the Earth-facing side of the moon. The
bulk of the lunar cratering took place 3.8
billion years ago, when the Earth and Moon where
closer together. That means that the Earths
solid angle was larger (although still fairly
small), but the gravitational effect was also
greater. Most important, your theory does not
explain the lunar seas, vast plains of relatively
young volcanic rock that appear primarily on the
lunar near side. Internal geologic processes,
possibly influenced by external events, erased
many craters and gave the moon its split
personality the real question is why those
processes were so lopsided.
Worlds Out of Balance
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The Moons Appearance
Homework
1. Read pages 556 - 561 2. Summarize Properties
and Features of the Moon
Worlds Out of Balance

• Include
• diagram on page 557
• physical data - diameter, density, etc.
• define bolded terms maria, mascons, rille,
  rays, regolith

3. Why is the moon dark-coloured in some areas
and light-coloured in others? Explain in
detail. 4. Page 560 2, 3, 4