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Chapter 30
Moons and Rings
Chapter 30, Section 1
30.1 The Earth’s Moon
How was the moon formed?
Introduction
Satellite: any body that orbits a larger body
 1957: Soviet Union launched Sputnik 1,
the Earth’s first artificial satellite.
 1958: U.S. launched Explorer 1.
 A natural satellite of any planet is called a
moon

Sputnik 1
Explorer 1
Questions

What is a satellite?
Satellite: any body that orbits a larger body

What country launched the first satellite?
1957: Soviet Union launched Sputnik 1
Lunar Info
Gravity on the moon is only one-sixth the
gravity of Earth.
 No atmosphere because the moon’s
gravity is too weak to hold gases.
 Daytime temp. 134 °C, nighttime -170 °C
 Lunar day is 29.5 Earth-days.

Questions

Discuss with your neighbor how much you
would weigh on the moon.
5 lunar features
1.
2.
3.
4.
5.
maria
rilles
craters
rays
highlands
-anorthosites
-breccia
-regolith
The Lunar Surface
Light and dark patches on the moon.
 Light areas are rough highlands made of
light-colored rock.
 Dark areas, called maria (MAHR-ee-uh)
 The maria are plains of solidified lava.
 Rilles are long, deep channels that run
through the maria.
 Rilles were probably lava channels when
the moon was volcanically active.

Questions

What are maria?


Maria are dark areas that are plains of
solidified lava.
What are rilles?

Rilles are long, deep channels that run
through the maria, they were probably lava
channels when the moon was volcanically
active.
Craters
The Moon’s surface is covered with bowlshaped depressions called craters
 Most were formed 4 billion years ago
 Debris that was thrown away from the
impact sites formed rays that extend in all
directions from the crater

Copernicus Impact Crater
Lunar Rocks

Anorthosites:
from lunar
highlands, lots
of calcium and
aluminum, lightcolored.
Regolith
Regolith: dust and small fragments that
cover the lunar surface.
 Depth of regolith varies from 1m to 6m

Breccia
Breccia: found in both maria and highlands
 They are fragments of other rocks that
have melted together.

Questions
 What
are regolith?
 Dust and small fragments that cover
the lunar surface
 What are breccia?
 Fragments of other rocks that have
melted together
Interior of the Moon

Seismographs
were placed on the
moon by Apollo
astronauts
between 19691972
Interior…see page 620
Recorded numerous weak quakes
 Crust facing Earth is 60km thick
 Crust facing away from Earth is up to
100km thick.
 Beneath crust is the mantle
 Mantle depth = 1000km
 Core: possibly molten, possibly iron, less
than 700km
 Almost no magnetic field, but local areas
of magnetism exist, suggesting a solid
core.

Stage 1
Giant-impact hypothesis: suggests the
Moon formed when a Mars-sized body
struck the Earth early in the history of the
solar system.
 The collision caused fragments to be
ejected up into space.
 These fragments eventually joined
together to form the Moon.

2nd stage
Moon was covered by an ocean of hot,
molten rock.
 As the Moon cooled, materials separated
by density.
 Heavier elements sank to the core.
 Lighter elements formed the mantle.

3rd stage
Outer surface of the Moon cooled and
formed a thick crust over the molten rock
 Debris left over from the formation of the
solar system struck the Moon, giving the
Moon its craters.
 Some impacts broke through the crust.
 Lava flowed through these breaks to the
surface and formed the smooth maria.

4th stage
3 billion years ago until now
 Impacts decreased to almost nothing
 Geologic activity stopped because of
cooling.

Questions

Discuss the stages of the formation of the
moon with your partner.
The Giant Impact,
as pictured in a
painting by William
K. Hartmann on the
cover of Natural
History Magazine in
1981. Copyright
William K.
Hartmann
Half an Hour
After the Giant
Impact, based
on computer
modeling by A.
Cameron, W.
Benz, J. Melosh,
and others.
Copyright William
K. Hartmann
Five Hours
After Impact,
based on
computer
modeling by A.
Cameron, W.
Benz, J.
Melosh, and
others.
Copyright
William K.
Hartmann
Moon Forming Out of Rings
Copyright William K. Hartmann
Studies of lunar rocks show that the moon originally
had a molten surface. As this so-called magma ocean
cooled, intense volcanism continued for about 900
million years. An early volcanic eruption is shown here.
Copyright William K. Hartmann
The Moon Today. This late afternoon scene on the moon
typifies the moon as it has been for about 3 billion years.
Volcanism has ended. Meteorite impacts are rare. The quiet
landscape awaits the return of human explorers. Copyright
William K. Hartmann