The Moon

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The Moon

• 28.2

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Reaching for the Moon

• Much of our knowledge of the Moon comes from
  explorations by space probes and astronauts.
• The first step was taken in 1957 with the launch
  of the first satellite, Sputnik I, by the Soviet
  Union.

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Reaching for the Moon

• In 1961, Soviet cosmonaut Yuri Gagarin became the
  first human in space.
• The United States Project Mercury launched the
  first American, Alan Shepard Jr., into space on
  May 5, 1961.

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Reaching for the Moon

• Project Gemini launched two-person crews into
  space, and on July 20, 1969, the Apollo program
  landed Neil Armstrong and Buzz Aldrin on the
  Moon, during Apollo 11.

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Lunar Properties

• The Moons radius is about 27 of Earths radius,
  and its mass is more than 1 of Earths mass.
• Most moons are much smaller than this.
• The Moons orbit is relatively farther from Earth
  than most moons are from the planets they orbit.

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Lunar Surface

• The albedo of the Moon, the amount of sunlight
  that its surface reflects, is very small (7).
• The sunlight that is absorbed by the surface of
  the Moon is responsible for the extreme
  differences in temperatures on its surface.
• 127C to -173C

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The Lunar Surface

• There is no erosion on the Moon except for
  impacts.
• The surface of the Moon consists of several
  features.
• Regions called highlands are light in color,
  mountainous, and heavily covered with craters.

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The Lunar Surface

• Regions called maria (mare) are dark, smooth
  plains.
• All of the craters on the Moon are impact
  craters, formed when objects from space crashed
  into the lunar surface.
• The material blasted out during these impacts
  fell back to the surface as ejecta.

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The Lunar Surface

• Some craters have long trails of ejecta, called
  rays, that radiate outward.
• Rilles are meandering, valleylike structures.

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Composition

• The Moon is covered in minerals similar to those
  of Earth, mostly silicates.

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History of the Moon

• The Moon is between 3.8 and 4.6 billion years
  old.
• During its first 800 million years the Moon was
  heavily bombarded which resulted into forming a
  layer of loose, ground-up rock, called regolith
  on the surface of the Moon.

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History of the Moon

• After the bombardment, lava welled up from the
  Moons interior and filled in the large impact
  basins to form maria.
• The Moon is twice as thick on the far side of the
  moon.

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Tectonics on the Moon?

• Scientists infer from seismometer data that the
  Moon, like Earth, has a layered structure, which
  consists of the crust, the upper mantle, the
  lower mantle, and the core.
• The Moon experiences a moonquake once a year, but
  scientists theorize that the Moon is not
  tectonically active.

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Formation Theories

• The capture theory proposes that as the solar
  system was forming, a large object ventured too
  near to the forming Earth, became trapped in its
  gravitational pull, and formed into what is now
  the Moon.
• The problem with that is that something would
  have to slow it down, and the moon and earth
  would have difference compositions.

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Formation Theories

• Another theory, called the simultaneous formation
  theory says the Moon and Earth formed at the same
  time and in the same general area which makes the
  materials the same.
• This theory does not account for the different
  amounts of iron on Earth and on the Moon.

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Formation Theories

• The most commonly accepted theory of how the Moon
  formed, the impact theory.
• The Moon formed as the result of a gigantic
  collision between Earth and a Mars-sized object
  about 4.5 billion years ago, when the solar
  system was forming.

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Formation Theories

• As a result of the collision, materials from the
  incoming body and from Earths outer layers were
  ejected into space, where they merged together to
  form the Moon.

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