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1 Describe the structure of the
moon
2. Describe its surface features
3. Summarize the hypothesis of
moon formation
•moon -a body that revolves around a planet and
that has less mass than the planet does.
•A natural satellite
•satellite a natural or artificial body that revolves
around planet.
•One of more than 96 moons in our Solar System
•The only moon of the planet Earth
Earth
Moon
7930 miles (12,756.3 km)
diameter
2160 miles (3476 km)
diameter
23 degree axis tilt (seasons!)
7 degree tilt (no seasons)
Surface temps –73 to 48 C (100 to 120F)
Surface temps - 107 C to –
153 C (224 F to –243 F)
Thick atmosphere, mild
greenhouse effect
No atmosphere
Liquid water – lots! - at
surface
No liquid water … Ice at
poles in shadows?
Birth of the Moon:
1.began when a Mars-sized “planetesimal” collided with
Earth more than 4 billion years ago.
2.The collision ejected chunks of Earth’s mantle into orbit
around Earth.
3. The debris eventually clumped together to form the
moon.
This hypothesis explains why moon rocks share many of
the chemical characteristics of Earth’s mantle.
3 major divisions
of the Lunar
interior
 Crust - average
thickness of
about 70
kilometers
 Mantle
 Core - radius is
between 300 and
425 kilometers

The side of the moon that faces Earth is called the near side,
while the side of the moon that faces away from Earth is
called the far side.
The moon’s crust is thicker one side than the other.
The crust on the near side is about 60 km thick. The crust on
the far side is up to 100 km thick.
The difference in thickness was caused by the pull of
Earth’s gravity during the formation of the moon.
Beneath the crust is the moon’s mantle. The mantle is
thought to be made of rock that is rich in silica,
magnesium, and iron.
Scientists think that the moon has a small iron core that has
a radius of less than 700 km.
Studies of the core have shown that the moon’s rotation is
not uniform and that the core is neither completely solid nor
completely liquid.
mare -a large, dark area of basalt on the moon
Any feature of the moon is referred to as lunar.
The light patches seen on the moon’s surface are
called anorthosites. The darker areas are called maria.
Maria are plains of dark, solidified lava which form
more than 3 billion years ago when lava slowly filled
basins that were created by massive asteroids
crater -a bowl-shaped depression that forms on the
surface of an object when a falling body strikes the
object’s surface or when an explosion occurs
The surface of the moon is covered with craters, rilles, and
ridges. Most of the craters formed when debris struck the
moon about 4 billion years ago.
Rilles -are long, deep channels that run through the
maria. Rilles are thought to be leftover lava channels from
the formation of the maria.
The moon’s surface also has several ridges, which are long,
narrow elevations of rock that rise out of the surface and
criss-cross the maria.
The moon’s surface is very susceptible to meteorite hits
because the moon has no atmosphere for protection.
Over billions of years, these meteorites crushed much of
the rock on the moon’s surface into a layer of dust and
small fragments called regolith.
The depth of regolith on the moon varies from 1 m to 6 m.
Lunar rocks are igneous, and most rocks near the surface are
composed mainly of oxygen and silicon.
Rocks from the lunar highlands are light-colored, coarsegrained anorthosites that contain calcium and aluminum.
Rocks from the maria are fine-grained basalts and contain
titanium, magnesium, and iron.
Breccia is found in both maria and the highlands. Lunar
breccia formed when meteorites struck the moon.
• 1960-1977 seismometers were tracking moonquakes, average of 5.5
on the Richter scale.
• There are 4 types of moonquakes:
1.Deep moonquakes (likely caused by tidal stresses caused by the
gravitational tug of war between the Earth, Moon and Sun.)
2.Meteorite induced tremors
3. Thermal quakes(freezing crust expands as it returns into sunlight after
two weeks of lunar night time)
4. Shallow quakes (due to landslides of rock down steep crater rims)
• 1-3 are generally mild and harmless
• Last long time some for 10minutes, earthquakes rarely surpass 2
minutes usually between 10-30seconds
No current plate tectonics
Moon has cooled to point of inactivity (for about 3
billion years now)
• So no current volcanoes
• current moonquakes not due to plate tectonics
•
•
1.Describe shape of the moon’s
orbit using apogee and perigee.
2. Describe the types of eclipses
and what is happening to the
Moon and Earth during them
 Earth and the moon revolve around each other.
Together they form a single system that orbits
the sun.
 The balance point of the Earth-moon system is
located within the Earth’s interior, because
Earth’s mass is greater than the moon’s mass.
 This balance point is called the barycenter. The
barycenter follows a smooth orbit around the
sun.
Apogee- in the orbit of a satellite, the point at which the satellite
is farthest from Earth
Perigee- in the orbit of a satellite, the point at which the satellite
is closest to Earth
When the moon is farthest from Earth, the moon is at apogee.
When the moon is closest to Earth, the moon is at perigee.
The orbit of the moon around Earth forms an ellipse, the distance
between Earth and the moon varies over a month’s time.
o Moon rotates once on its axis every 27.3 days
o One lunar day equals 29.5 Earth days
o due to moon and Earth both revolving around the sun in
addition to the moon going around the Earth.
The moon appears to rise and set at Earth’s horizon
because of Earth’s rotation on its axis.
The moon rises and sets 50 minutes later each night. This
happens because of both Earth’s rotation and the moon’s
revolution.
While Earth completes one rotation each day, the moon
also moves in its orbit around Earth. It takes 1/29 of
Earth’s rotation, or about 50 minutes, for the horizon to
catch up to the moon.
The moon’s revolution around Earth and its
rotation on its axis take the same amount of time.
Because the rotation and revolution take the same
amount of time, observers on Earth always see the
same side of the moon.
The part of the moon illuminated by sunlight
changes as the moon orbits Earth.
• The Sun always illuminates half of the moon
and half of the Earth.
• The near side of the moon can be completely
illuminated, partially illuminated or completely
darkened depending on where it is in its orbit
• This gives the phases of the moon
•
eclipse -an event in which the shadow of one celestial
body falls on another
Bodies orbiting the sun, including Earth and its moon,
cast long shadows into space. An eclipse occurs when
one body passes through the shadow of another.
Shadows cast by Earth and the moon have two parts: the
inner, cone-shaped part of the shadow called the umbra
and the outer part of the shadow called the penumbra.
solar eclipse- the passing of the moon between Earth and
the sun; during a solar eclipse, the shadow of the moon
falls on Earth.
During a total solar eclipse, the sun’s light is completely
blocked by the moon. The umbra falls on the area of Earth
that lies directly in line with the moon and the sun.
Outside the umbra, but within the penumbra, people see a
partial solar eclipse. The penumbra falls on the area that
immediately surrounds the umbra.
During a total solar eclipse, the sunlight that is not
eclipsed by the moon shows the normally invisible outer
layers of the sun’s atmosphere.
This causes what is known as the diamond-ring effect,
because the sunlight often glistens like the diamond on a
ring.
If the moon is at or near apogee during a solar eclipse,
the moon’s umbra does not reach Earth. This causes an
“annual eclipse” in which a thin ring of sunlight is visible
around the outer edge of the moon.
The brightness of this ring prevents observers from seeing
the outer layers of the sun’s atmosphere (corona).
lunar eclipse - the passing of the moon through
Earth’s shadow at full moon
A lunar eclipse occurs when Earth is positioned
between the moon and the sun and when Earth’s
shadow crosses the lighted half of the moon.
When only part of the moon passes into Earth’s
umbra, a partial lunar eclipse occurs.
When the entire moon passes through Earth’s
penumbra, a penumbral eclipse occurs.
1. Identify and summarize the pattern of moon
phases
2. Understand and explain why the moon goes
through phases
phase - the change in the illuminated area of one celestial
body as seen from another, celestial body
phases of the moon are caused by the changing positions of
Earth, the sun, and the moon
As the moon revolves around Earth, different amounts of the
near side of the moon, which faces Earth, are lighted.
Therefore, the apparent shape of the visible part of the moon
varies. The varying shapes are called phases.
The moon passes through four major shapes during
cycle that repeats itself every 29.5 days.
• The phases always follow one another in the same
order.
• New Moon
• First Quarter
• Third Quarter
• Full Moon
•
•
•
•
The lighted side of the moon faces away form
the Earth.
This means the Sun, Earth, Moon are almost in
a straight line
The moon that we see looks dark
•
•
The right half of the Moon appears lighted
and the left side of the Moon appears dark.
During the time between the New Moon and
the First Quarter Moon, the part of the Moon
that appears lighted gets larger and larger
every day, and will continue to grow until the
Full Moon.
•
•
The left half of the Moon appears lighted, and
the right side of the Moon appears dark.
During the time between the Full Moon and
the Last Quarter Moon, the part of the Moon
that appears lighted gets smaller and smaller
every day. It will continue to shrink until the
New Moon, when the cycle starts all over again.
The lighted side of the Moon faces the
Earth.
• This means that the Earth, Sun, and Moon
are nearly in a straight line, with the Earth in
the middle.
• The Moon that we see is very bright from the
sunlight reflecting off it.
•
•
Between the four main
phases are crescent and
gibbous shaped moons
•
These phases include
• Waxing crescent
• Waxing gibbous
• Waning gibbous
• Waning crescent
• Crescent - The Moon appears
to be partly but less than onehalf illuminated by direct
sunlight.
• Gibbous - The Moon appears
to be more than one-half but
not fully illuminated by direct
sunlight.
Waxing- When the size of the lighted part of the moon is
increasing
When a sliver of the moon’s near side is illuminated, the
moon enters its waxing-crescent phase.
When a waxing moon becomes a semicircle, the moon
enters its first-quarter phase.
When the lighted part of the moon’s near side is larger than a
semicircle, the moon is in its waxing-gibbous phase.
At full moon, the entire near side of the moon is
illuminated by the light of the sun.
Waning - When the lighted part of the near side of the moon
appears to decrease in size
When the moon is waning, but is still larger than a
semicircle, the moon is in the waning-gibbous phase.
When the moon is waning, and it is a semicircle, the moon enters
the last-quarter phase.
When only a sliver of the near side is visible, the moon enter the
waning-crescent phase. After this phase, the moon becomes
a new moon, in which no lighted area of the moon is
visible from Earth.
New moon
Waxing crescent
First quarter
Waxing gibbous
Full moon
Waning gibbous
Third quarter
Waning crescent
Starts at new
moon again
e moon revolves around Earth in 27.3 days, however, the period from one new moon to the next one is 29.5 days.
moon revolves around Earth in 27.3 days, however,
the period from one new moon to the next one is
29.5 days.
This difference of 2.2 days is due to the orbiting of
the Earth-moon system around the sun.
In the 27.3 days in which the moon orbits Earth, the
two bodies move slightly farther along their orbit
around the sun.
So, the moon must go a little farther to be directly
between Earth and the sun. About 2.2 days are
needed for the moon to travel this extra distance.
Bulges in Earth’s oceans, called tidal bulges, form because
the moon’s gravitational pull on Earth decreases with
distance from the moon.
As a result, the ocean on Earth’s near side is pulled toward
the moon with the greatest force.
The solid Earth experiences a lesser force.
These differences cause Earth’s tidal bulges. Because
Earth rotates, tides occur in a regular rhythm at any
given point on Earth’s surface each day.