Earth’s Moon
How did our Moon form?
and
What’s been happening since?
What do you see?
Evidence a model must
explain
Moon is less dense than the
rocky planets (Mercury,
Venus, Earth, Mars) … it’s
“lighter”. Less iron than Earth
Moon is unusually big for a
satellite
Earth/Moon system has a lot of
angular momentum (spin +
orbital motion)
Chemical composition similar to
Earth’s mantle
A tilted orbit relative to Earth’s
path around the Sun
How Did the Moon Form?
Movie Time!
Movie of lunar evolution + tour from LRO
Find the video here:
http://svs.gsfc.nasa.gov/vis/a010000/a010900/a0
10930/evol_and_tour_ipod_lg.m4v
Hypothesis accepted by most planetary
scientists since mid-1980s:
Wham Moon!
The GIANT
Impact
Hypothesis
Explore Activity!
Lunar Geologic History
4.5 billion years ago, our Moon forms
(lunar rocks and meteorites)
The Magma Ocean
Explore Activities! Moon Mix!, Recipe for a Moon
Magma Ocean / Lunar Highland Rocks
Anorthosite (a type of feldspar) – mostly CaAl2Si2O8
4.44-4.51 Billion Years Old
Explore Activity!
Splat!
Late Heavy Bombardment
“Nice Model”
4.5 billion years ago
3.9 billion years ago
3.85 billion years ago
Intense period of impacts on Moon (and everything else in Solar
System) by comets and asteroids
Lunar Impact Basins
(really big craters)
Rim of Imbrium Basin
Orientale Basin
Big, frequent impacts until 3.8 billion years ago
Impact events continue across our solar system today!
Lunar Impact Rocks
Breccia
Lunar Geologic History
Filling in the Basins
Mare Imbrium
SW Mare Imbrium
Volcanism after impacts – most before 3 (to 1) billion years ago
Explore Activity! Moon Ooze
Lunar Basin Rocks
Basalt
3.3 Billion Years Old
Volcanoes on the Moon
There are a few
actual volcanoes
on the Moon
Not nearly as
many as Earth!
No longer active
Lunar Geologic History - Basins
Dark, smooth Maria
Basalt – fine grained dark igneous
rock rich in iron and
magnesium (heavy stuff that
sank in magma ocean)
Few hundred meters thick
Rocks are 4.3 to 3.1 billion years
old … flows as recently as 1
billion years ago
A Brief Summary of Lunar Geologic History
Moon Mix!
Splat!
Moon Ooze
Impact Paintings
and …
Tidal Evolution
The Moon is far from the Earth! Why?
The Moon is moving away from Earth by 3.8 centimeters each year!
On average, the Moon is about 7 feet further away than when I was born
 Moon was close to Earth billions of years ago.
All quiet except for impacts...
Like this one in 2005 that made a 9 foot crater …
0.15 seconds
Explore Activity!
Lunar Geologic History – Recent Activity
Trails of the
Apollo 12
Astronauts
Explore Activity!