Download The Moon

THE MOON
28.2
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.
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.
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.
Lunar Properties
 The Moon’s radius is about 27% of Earth’s
radius, and its mass is more than 1% of
Earth’s 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.
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.
 127°C to -173°C
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.
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.
The Lunar Surface
 Some craters have long trails of ejecta, called
rays, that radiate outward.
 Rilles are meandering, valleylike structures.
Composition
 The Moon is covered in minerals similar to
those of Earth, mostly silicates.
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.
History of the Moon
 After the bombardment, lava welled up from
the Moon’s interior and filled in the large
impact basins to form maria.
 The Moon is twice as thick on the far side of
the moon.
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.
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.
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.
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.
Formation Theories
 As a result of the collision, materials from the
incoming body and from Earth’s outer layers
were ejected into space, where they merged
together to form the Moon.