Chapter 22 Section 3

Earth’s Moon

Earth vs. Moon

3,475 km

12,756 km

• Earth has 1 natural satellite the Moon

• No specific name other than Moon

• Unusual because of size in comparison to parent planet (Earth)

• Density is 3.3 X that of water (= to mantle rocks on E)• M core=

small• E density is

5.5 X that of water

• Gravity 1/6th of E• 150 lb = 25 lb

Moon is ~1/4th the size of

Earth!

~238,000 miles

Earth’s Tides & The Moon

A Trip Inside the Moon

Apollo Missions• Most of Moon information gathered from Apollo missions (6 landed on Moon’s surface 1969-1972).• CBS News Coverage Apollo 11

Space Race1955-1972

• What was the space race?• Who won the space race?

Surface of the Moon• Craters: round depressions

– Produced by impact of rapidly moving debris– Many craters present due to lack of atmosphere

& no tectonic activity– Rays: “splash” marks (dust) radiated from

crater on impact (like sun “rays”)

• Highlands: densely pitted, light-colored areas (mountain-like)– Highest peaks ~8 km (1 km shorter than Mt.

Everest)

• Maria: dark, relatively smooth areas made of basaltic lava (singular mare latin for sea)– Originated from asteroids punctured surface

magma slowly seeped from below surface– Rilles: long channels that were once filled with

ancient lava flows (collapsed lava tubes [like a hose with no H2O flowing])

• Regolith: soil-like layer on surface; gray debris/dust from impact; ~3 m thick

What does the surface of the Moon look like?

Principle of Cross-Cutting• Why must have the rays (rayed craters)

formed after the maria & rayless craters?

• They cross-cut them!• Older cross is cut by

younger; the one cutting is younger than the one being cut

• Rock A (cutting) is younger than Rock B (being cut)

Moon’s First Birthday• Origin of Moon: Impact Theory

– During solar system formation– Body about the size of Mars impacted Earth– Liquefied Earth’s surface & ejected crustal & mantle

rock • This debris entered orbit around Earth & accreted to form

Moon

• Support: 1. Iron-poor mantle & crustal rocks Moon’s core2. Zinc isotopes

• Traces of zinc found on Moon more heavy/less light in comparison to Earth

• Moon went through intense evaporation (heat) event early on

• Intense temperatures allowed lighter zinc isotopes to evaporate leaving behind more of the heavier zinc isotopes

Impact Theory

Timeline of Moon’s Life1. Formation: formed

very “quickly” (few million yrs)

2. Early: formed as liquid and differentiated– Meteor impacted

solid crust ~4 billion yrs ago (highlands)

3. Volcanic: lava flows filled basins caused by impacts (~3 billion yrs ago) creating maria

4. Inactive: geoglocially dead for last 3 billion yrs (core solidified)