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Lunar Geology
John Young from Apollo 16, April 1972
Harrison Schmidt 12/1972 Apollo 17
Relative Size and Distance
Object
Size
Moon
1.0 units
Earth
3.7 units
Separation
110.6 units
Sun
400.5 units
Relative Size of Earth and Moon
From which side is the
sun light coming?
Moon Data
Note the Picture Difference
Naked eye
view of the
Moon
?
Can You Spot the
”Face of the Man in the Moon”?
Tycho Crater
Young crater
Circular Ray crater
85 kilometers across
Clearly visible from Earth
Close to the southern polar
Surrounded by a bright ejecta blanket.
Clavius
232 km = 144 miles
4.9 km deep
South of Tycho
Palomar 200 inch
Mare Imbrium
Largest of the 14 dark
plains of the near side
of the Moon
London to Rome
Rilles
Apollo 11 site near
the center of the top
edge
Apollo 11 Landing Site
Clementine Images at Different Wavelengths
Moments before impact with Alphonsus
3/24/65
Alphonsus is about 129 km wide
Low Lands and High Lands
Surveyor 3 Lands on the Moon
Landed in 4/67
Visited in 11/69
Apollo 12 Astronauts
Allen Bean Pictured
Pete Conrad Photographer
Apollo 15
Lunar Rover
Buzz Aldrin, Seismometer Detected Moonquakes
Regolith
Billions of years of
pounding by space
debris have pulverized
the Moon’s surface
which is now bone dry
yet sticks together like
wet sand.
Tides
Mare Basalt – Gas dissolved under pressure forming bubbles
Anorthosite – Highlands, perhaps part of the original lunar crust.
Breccias – formed by compression after heating due to impacts
Orbits of Jupiter and Saturn
may have shifted about 4
billion years ago causing
gravitational perturbations on
the asteroid belt.
Where Did the Moon Come From?
Lunar Colonization
Key Ideas
• Appearance of the Moon: The Earth-facing side of the
Moon displays light-colored, heavily cratered highlands
and dark-colored, smooth-surfaced maria. The Moon’s
far side has almost no maria.
• Virtually all lunar craters were caused by space debris
striking the surface. There is no evidence of plate
tectonic activity on the Moon.
Key Ideas
• Internal Structure of the Moon: Much of our knowledge
about the Moon has come from human exploration in the
1960s and early 1970s and from more recent
observations by unmanned spacecraft.
• Analysis of seismic waves and other data indicates that
the Moon has a crust thicker than that of the Earth (and
thickest on the far side of the Moon), a mantle with a
thickness equal to about 80% of the Moon’s radius, and a
small iron core.
Key Ideas
• The Moon’s lithosphere is far thicker than that of the Earth.
• The lunar asthenosphere probably extends from the base
of the lithosphere to the core.
• The Moon has no global magnetic field today, although it
had a weak magnetic field billions of years ago.
Key Ideas
• Geologic History of the Moon: The anorthositic crust
exposed in the highlands was formed between 4.3 and
4.0 billion years ago.
• An era of heavy bombardment formed the maria basins
between 4.0 and 3.8 billion years ago, and the mare
basalts solidified between 3.8 and 3.1 billion years ago.
• The Moon’s surface has undergone very little change
over the past 3 billion years.
Key
Ideas
Key Ideas
• Meteoroid impacts have been the only significant
“weathering” agent on the Moon.
• The Moon’s regolith, or surface layer of powdered and
fractured rock, was formed by meteoritic action.
• All of the lunar rock samples are igneous rocks formed
largely of minerals found in terrestrial rocks.
• The lunar rocks contain no water and also differ from
terrestrial rocks in being relatively enriched in the
refractory elements and depleted in the volatile
elements.
Key Ideas
• Origin of the Moon: The collisional ejection theory of
the Moon’s origin holds that the proto-Earth was struck
by a Mars-sized protoplanet and that debris from this
collision coalesced to form the Moon. This theory
successfully explains most properties of the Moon.
• The Moon was molten in its early stages, and the
anorthositic crust solidified from low-density magma that
floated to the lunar surface. The mare basins were
created later by the impact of planetesimals and filled
with lava from the lunar interior.
• Tidal interactions between the Earth and Moon are
slowing the Earth’s rotation and pushing the Moon away
from the Earth.