1. LUNAR FORMATION TABLE OF CONTENTS What is Lunar Formation? Formation Theories Giant Impact Theory Links Image from NASA Earth’s Moon

2. LUNAR FORMATION WHAT IS LUNAR FORMATION? Lunar formation is the process in which a moon is created. There are several theories on how Earth’s moon was formed, but nobody is sure what really happened. Image from NASA Earth’s Moon from South Pole Back to Table of Contents

3. LUNAR FORMATION FORMATION THEORIES There are four main theories of lunar formation: Fission Theory: The moon was part of the Earth, but somehow broke off and became its own celestial body. Capture Theory: The moon, which was formed elsewhere, traveled through Earth’s orbit and got caught in its gravity field. Back to Table of Contents Image from NASA Earth’s Moon More Theories

4. LUNAR FORMATION MORE FORMATION THEORIES Condensation Theory: Both the Earth and the moon formed at the same time in the same area. Giant Impact Theory: The dominant theory in which a large celestial body slammed into the Earth. The moon was created out of the debris. Back to Table of ContentsPrevious Earth and its Moon Image from NASA

5. LUNAR FORMATION GIANT IMPACT THEORY The Giant Impact Theory, also known as the “Big Whack,” is the dominant lunar formation theory. In this theory, a Mars- sized “protoplanet” collided with Earth, releasing debris which eventually formed the moon. Back to Table of ContentsMore on Giant Impact Theory Artist’s interpretation of the impact.

6. LUNAR FORMATION MORE GIANT IMPACT THEORY At first, the theory was heavily criticized, but with the development of models and simulations, the theory became more widely accepted. Since a collision on this scale is hard to model, computer simulations have been used to try to replicate the event. Giant Impact Theory’s IssuesPreviousBack to Table of Contents Image from ClassZone Screenshot from a Giant Impact simulation. Click the image to view the animation.

7. LUNAR FORMATION GIANT IMPACT ISSUES No simulation has yet been able to confirm the theory. Often in simulations, the Earth after collision is left spinning too fast or its mass is decreased by too much. The theory does not explain the Moon’s lack of iron and siderophilic (iron- liking) elements. Back to Table of Contents Previous Simulated image of the moon’s accretion. Image from DTA

8. LUNAR FORMATION LINKS http://www.swri.org/3p ubs/ttoday/spring99/m oon.htmhttp://www.swri.org/3p ubs/ttoday/spring99/m oon.htm http://www.classzone. com/books/earth_scie nce/terc/content/visual izations/es2501/es250 1page01.cfm?chapter _no=visualizationhttp://www.classzone. com/books/earth_scie nce/terc/content/visual izations/es2501/es250 1page01.cfm?chapter _no=visualization Image from NASA False Color Image of the Moon Back to Table of Contents