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Chapter 24 – Earth’s Moon
Ms. Martel
Getting to the Moon
• Getting a spacecraft to the moon is a complex task.
– The rocket used must be large enough to put the spacecraft into Earth’s
orbit before the rocket stops firing.
– Once the spacecraft is in Earth’s orbit, another rocket fires toward the point
where the moon will be when the spacecraft gets there.
– The aiming and firing must be precise, otherwise the spacecraft will miss the
moon and go into orbit around the sun.
The First Spacecraft to the Moon
• The first spacecraft to leave Earth orbit and reach lunar orbit was part of
the Luna series launched by the former Soviet Union.
• The United States launched the Pioneer series at the same time,
however, their first attempts were unsuccessful.
• In 1961, President Kennedy made it a national goal to land an astronaut
on the moon and return them safely to Earth.
Mercury and Gemini
• The first American spacecraft to carry an astronaut was
the Mercury Series. The series had 9 different space
shuttles that were used to practice orbiting ships around
the Earth.
• The Gemini spacecrafts were designed for two
astronauts.
– These spacecrafts had two purposes:
• First was to find out if humans could survive and work in the
weightlessness of space for the 10 days needed to go to the moon and
back.
• The second was to train astronauts to maneuver the spacecraft.
Apollo
• The Apollo missions accomplished President Kennedy’s objectives.
• In 1969, Apollo 11 astronaut Neil Armstrong and Edwin Aldrin Jr became
the first people to walk on the moon.
• The Apollo astronauts brought back a total of 380 kg of rock and soil
samples.
• They left behind instruments to measure things such as moonquakes,
magnetic field, solar wind particles etc.
The Space Shuttle
• Unlike its predecessors Mercury,
Gemini, and Apollo, the versitile space
shuttle is designed to be reused. Each
shuttle has 3 main units:
– The orbiter, or the airplane body
– The external tank, which feeds
propellants to the engine during the first
stage of flight.
– Two solid rocket boosters that provide
the energy to the initial lift-off. These
are discarded about 10 mins after the
launch.
Properties of the Moon
• The moon’s diameter is 3476 km, or more than one fourth Earth’s
diameter.
• The moon’s low gravity and low escape velocity means its much easier
to launch a spacecraft from the moon than from Earth.
• The equipment left over from the Apollo aircraft continued to operate
for 8 years, and recorded enough data for scientists to develop a model
of the moon’s interior.
– The moon just like Earth
has a layered structure.
The Origin and History of the
Moon
• One likely theory based on lunar data proposes that the moon
formed about 4.6 billion years ago from a collision between Earth
and a Mars-sized object.
– In theory, the collision broke through the solid crust and splashed a
huge mass of molten rock into space, which cooled and became to
moon.
– Then, showers of rock-like particles bombarded the moon’s surface.
This bombardment lasted for hundred of millions of years.
– Hot lava then poured out of gaps in the great basins. These eruptions
continued for nearly a billion years.
– Finally the moons became geologically inactive, this has been the
case for 3 billion years.
Lunar Rocks: Evidence of the
Moon’s History
• Lunar rocks differ from Earth’s in
several ways. Lunar rocks contain no
water at all.
• They contain more elements with
high melting points such as titanium,
rather than gas elements such as
nitrogen.
• Radioactive dating has been used to
find the age of lunar rocks. Most are
between 4-4.3 byo, however the
oldest ones are dated at 4.6 byo.
•
The
Lunar
Maria
Galileo thought the dark spot on the moon were seas, and thus called
them Lunar Maria (the Latin word for seas).
• However there is no signs that indicate the moon ever had water.
– The Maria are smooth plains with huge circular basins.
– The first spacecraft's to circle the moon found that the moon’s gravity was
greater over some of the more circular maria.
– These areas of higher gravity are called mascons for “mass concentrations.”
– Rilles are long deep clefts or cracks running through maria bedrock.
The Lunar Highlands
• The final 3 Apollo flights
landed in lunar highlands.
These areas appear brighter
than the maria because their
rocks are lighter and reflect
more sunlight.
• Lunar scientists believe that
the lunar highlands were
thrown up by impact craters.
Lunar Soil
• Lunar soil is not really soil.
– Scientists prefer t call it regolith,
which means loose rock
materials.
– Unlike Earth soil, regolith
contains no water or organic
material.
– Regolith was made by the
smashing impact of meteoroids
of all sizes.
The Moon’s Orbit
• The moon revolves around the Earth from west
to east in an elliptical orbit.
• It takes 27 1/3 days to revolve around the Earth.
• The sun’s diameter is nearly 400 times the
moon’s diameter, yet they both appear to be
about the same size in the sky.
– The reason is that the sun is nearly 400 times farter
away from Earth than the moon.
Moonrise and Moonset
• The moon rises in the east and sets in the west, like
the sun’s rising and setting.
– As the moon moves around Earth, it can be seen rising at
a different time each night.
– The moon moves about 13° eastward along its orbit every
day. Thus the Earth must rotate an extra 13° more than
360° to see the moon rise each night.
– This takes approximately 50 minutes, which means the
moon rises about 50 minutes later each day and sets
about 50 minutes later as well.
The Moon’s Phases
• The phases of the moon are the daily changes
in the moon’s appearance.
• This occurs for two reasons:
– 1. the moon is seen by reflected sunlight.
– 2. the moon is in orbit around Earth.
• 1) New Moon
• 2) Waxing Crescent
• 3) Waxing Quarter
• 4) Waxing Gibbous
• 5) Full Moon
• 6) Waning Gibbous
• 7) Waning Quarter
• 8) Waning Crescent
Lunar Eclipses
• The shadow cast by any opaque object has two parts:
– The umbra is the total shadow
– The penumbra is the partial shadow surrounding the umbra.
• The lunar eclipse can occur only at the full moon phase
• The moon remains visible during its eclipse, but it has a dusky
red or coppery colour.
• On the average, at least one total lunar eclipse occurs every
year.
Solar Eclipse
• A solar eclipse occurs when the moon’s umbra reaches
Earth’s surface, and can only occur during the new moon.
• Locations on Earth within the umbra experience a total solar
eclipse
– At that time, the moon blocks the entire photosphere of the sun.
The sky is dark, bright stars and planets can be seen with the
unaided eye.
The Moon and Tides
• The daily rise and fall of the ocean waters are called tides.
• Tides are unusually large during the new moon and full moon
phases, and unusually small during quarter moon phases.
• Sir Isaac Newton first explained how the gravity of the moon
causes tides.
Spring and Neap Tides
• The sun has the same kind of effect on Earth’s water’s
as does the moon.
– However, because the sun is so much farther away, the sun’s
effects are only half that of the moons.
– At new moon and full moon, we have spring tides, where
high tides are especially high and low tides are especially
low.
– At quarter phases of the moon, we have neap tides, where
high tides are not very high and low tides are not very low.