Earth’s MoonHow did our Moon form?

andWhat’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/a010930/evol_and_tour_ipod_lg.m4v

Hypothesis accepted by most planetary scientists since mid-1980s:

Wham Moon!The GIANT

Impact Hypothesis

Explore Activity!

4.5 billion years ago, our Moon forms (lunar rocks and meteorites)

Lunar Geologic History

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 BasinBig, 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

SW Mare ImbriumMare 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No longer active

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

Lunar Geologic History - Basins

A Brief Summary of Lunar Geologic History

Moon Mix!Splat!

Moon OozeImpact 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 …

Explore Activity!0.15 seconds

Lunar Geologic History – Recent Activity

Explore Activity!

Trails of the Apollo 12

Astronauts