Transcript Document

Lunar Oddities
and
The Origin of the Moon
Lunar Oddities
There are two things that make our Moon unique
among moons:
1. It orbits at a 5° from the plane of the Earth’s Orbit
and not in the plane of the equator.
Most moons orbit right along the planet’s Equator
2. It is quite large when compared to Earth at about
1/81st of Earth’s mass.
Most are about 1/1000th of the mass of the planet
they orbit.
Origin Hypotheses
Before Apollo 11 brought back rocks from the moon
there were three hypotheses to explain the Moon’s
origin. From each a prediction could be made about
the composition of lunar rocks.
1. The Moon is a small planet captured by Earth’s
gravity, so… the rocks should be unlike Earth rocks.
2. Earth and the Moon formed as “twin” planets,
so…the rocks should be similar to Earth’s.
3. The Moon began as a bulge that spun off the Earth,
so…Earth and Moon rocks should be almost
identical
Lunar Rocks
The composition of the Lunar Rocks brought back was
a complete surprise, not matching any of the
hypotheses! A new one was needed!
The rocks had a lot of High-melting temperature
materials, and very little low-melting temperature
materials.
The High-melting Temperature materials matched
Earth perfectly.
The material for the Moon must have come from Earth
And then been heated to a very high temperature
before cooling
The “Violent Birth” Hypothesis
A Mars-sized planet struck the Earth early in its
history. Heat from the collision melted part of the
Earth. Material was ejected; some of it formed the
Moon.
The Low-temperature melting materials vaporized
during the collision leaving the higher melting
temperature materials to form the Moon’s rocks.
This Explains both the orbital and composition
oddities of the Moon.