Respond to the following: How did the moon get there? In your notes… Respond to the following: How did the moon get there?

Capture Theory Capture- A large object wandered into our early solar system and was captured in the Earth’s gravitational field. Problems: What could slow the object down enough for the Earth to grab on to it? Why does the Moon have a similar composition? Both the Earth and the “rogue body” were fully formed Rogue body wandered into our solar system & was captured by Earth’s gravitational pull Problem – Earth’s gravitational pull isn’t strong enough to slow a body the size of the moon down enough to capture it into orbit. The moon would have kept on going. Problem – The moon is made up of the same materials as Earth’s crust and we don’t find that anywhere else in the solar system.

Fission Theory That the Earth was spinning so quickly that a bulge formed and was thrown off to form the moon. Problem – no evidence that the Earth was ever spinning that fast. If it were, why did the moon form where it is; not further away? While Earth was still in a molten state early in it’s formation, it was spinning so fast that a “magma bulge” formed and was flung off into space This magma bulge eventually cooled and became our moon

Co-accretion or Simultaneous Formation Simultaneous Formation- The Moon and Earth formed at the same time. Problems: The Earth is iron rich and the Moon isn’t. The moon is younger than the Earth. In the area where we are in space, the Earth and moon both formed at the same time and were made of the same materials available in the area Problem – Earth has a huge iron core compared to the size of Earth. The moon has a very tiny iron core. If they both formed at the same time from the same materials the iron would most likely be more evenly distributed Problem – Since astronauts brought back moon rocks during the Apollo missions, radio carbon date testing has been done on samples that confirm the moon is younger than the Earth. They did not form at the same time. 5

Most accepted theory today! Impact Theory The Impact Theory of the moon’s formation Earth’s moon formed from a collision between the early Earth and a Mars-sized object Most accepted theory today! Earth was a formed body in space Impactor was Mars-sized Hit Earth at an off-center angle and almost missed hitting Earth Impactor was absorbed into Earth’s core and thought to be made of the same materials as Earth After impact, Earth grew by ~ 25% Ejected material was thrown outside the Roche Radius and began to orbit Earth Earth developed a ring system Moon eventually coalesced from ejected material in orbit Problem – There is no evidence (chemical composition) of a huge impactor. Where is any material that is not found anywhere else on Earth? Was the impactor an exact compositional duplicate of Earth?

EVIDENCE Contain similar rocks Moon rocks lack water – evaporated in space as a result of high temperatures during impact. Density of the moon is lower that Earth’s ( moon is made of crust and mantle material) Moon - small iron core

Theories for Formation of the Moon IMPACT THEORY Video is 6:25 Earth was a formed body in space Impactor was Mars-sized Hit Earth at an off-center angle and almost missed hitting Earth Impactor was absorbed into Earth’s core and thought to be made of the same materials as Earth After impact, Earth grew by ~ 25% Ejected material was thrown outside the Roche Radius and began to orbit Earth Earth developed a ring system Moon eventually coalesced from ejected material in orbit

OTHER THEORIES Of Lunar Formation

Moonlet Condensation Theory Earth struck by many comets/asteroids in early solar system formation Ejected material formed rings around the Earth each time Rings condensed into moonlets Moonlets eventually collided/merged with each other Similar to Impact Theory except that instead of 1 giant impact forming a huge debris ring that coalesced into the moon, many small impacts created small debris rings that coalesced into small moonlets. Over time, these moonlets coalesced into the moon we see today. Scientists who proposed this theory argue that if a huge Mars-sized object struck Earth, there should be at least some remnants of differing chemical composition among the rocks on Earth and our moon. Where did the pieces from that huge impactor go? (This presumes that Earth and the mars-sized object were not already made of the same materials as an “Earth Twin” planet

EVIDENCE Contain similar rocks Moon rocks lack water – evaporated in space as a result of high temperatures during impact. Density of the moon is lower that Earth’s ( moon is made of crust and mantel material) Moon - small iron core NO evidence of the “Impact Theory” impactor found Impactors hit Earth at various angles but always appropriate to throw enough debris into space Ejected material was thrown outside the Roche Radius and began to orbit Earth Material Earth developed a ring system Moonlet formed Another impact happened and blasted more material beyond the Roche radius Another moonlet formed Process repeats forming many moonlets Moon eventually coalesced from moonlet material in orbit NOTE: This is a brand new theory. It is still being evaluated at this time so no specific problems with this theory have yet been identified.

What are some major observations/noticeable features of the moon? What do you believe some of these features may be or be caused by? Maria Highlands Maria are dried lava beds left over from early volcanism that existed on the early moon and are at lower elevation than the highlands Highlands are more heavily cratered than the mare (seas) on the moon and are at higher elevation. They reflect more sunlight and are brighter on the surface Craters form when objects from space impact on the lunar surface and create a “divot” Craters

So, the same side of the moon is always facing us! Earth’s Moon Features 3,475 km (2,150 miles) in diameter (1/4 of Earth’s) Similar to Earth’s mantle rocks (crust) Revolution 27 days, 8 hours Rotation 27 days, 7.2 hours So, the same side of the moon is always facing us! Tidally locked

Measurement Earth Moon Mean diameter 12,742 km 3,476 km Volume 1.08321 x 1012 km3 2.199 x 1010 km3 Mass 5.9736 x 1024 kg 7.349 x 1022 kg Mean density 5.515 3.342 Surface gravity 9.78 m/s2 1.62 m/s2 Escape velocity 11.2 km/s 2.38 km/s Visual albedo 0.367 0.12 Visual magnitude -3.86 +0.21 The Moon has approximately 1/4 Earth's diameter, 1/50 Earth's volume, and 1/80 Earth's mass. Earth is very dense overall (it is the densest planet in the Solar System), but the Moon is light for its size. The difference is partly because Earth has a large core of iron and other heavy metallic elements, while the Moon has only a small core, if it has a core at all. The Moon's surface gravity is 1/6 of Earth's, and escape velocity from the surface is about 1/5 of Earth's.

Apollo 15 Feather and Hammer Apollo 14 Golf Feather & Hammer video works

Locations of Apollo missions Most are in Maria

Cartoon Create a cartoon of 3 or more frames which depicts the theory of moon formation you most agree with. Give a written description of what is happening in each slide. Discuss why you chose this theory of moon formation.