Lunar Oddities and The Origin of the Moon

2. Lunar Odditiesand The Origin of the Moon

3. Lunar Oddities There are two things that make our Moon unique among moons: • 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.

4. 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

5. 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

6. 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. This predicted a small metallic core for the Moon…which was confirmed.