1. The Earth and Its Moon
Part 2: The Earth’s Moon

2. Men on the Moon
The Apollo space program’s objective was to land men on the moon and bring them safely back home.
1st moon landing was July 20, 1969 in the Sea of Tranquility
From 1969 through 1972, 12 men from 6 missions walked on the moon.
Neil A. Armstrong, commander Michael Collins, command module pilot Edwin E. Aldrin, Jr., lunar module pilot

3. The Moon’s Characteristics
Diameter: 3476km (about ¼ Earth’s)
Mass: about 1/80th that of the Earth
Gravity: about 1/6th that of Earth
Average Distance from Earth: 363,301km
Comparative sizes of the Earth and the Moon, as imaged by Deep Impact in September 2008 from 50 million km away. Credit: NASA
Moon Facts:

4. The Moon’s Characteristics
The surface temperature at the equator during the day is 134oC, and at night is ­­-153o C.
The moon is not round, but egg shaped with the large end pointed towards earth. 
The moon has no significant atmosphere or clouds.
Full Moon photograph taken from Madison, Alabama
Photo Credit: Gregory H. Revera

5. The Moon’s Structure Similar to Earth’s
Iron-rich inner core with a radius of nearly 150 miles
Fluid, primarily liquid-iron, outer core
A partially molten boundary layer around the core
Mantle
Crust – 60 km thick
Regolith: layer of dust, soil, and broken rock covering most of the moon
Regolith layer is anywhere from 3-20m thick; formed by the impact of meteors over billions of years.

6. Features of the Moon Highlands: mountain ranges
Maria (MAHR-ee-uh; singular-mare; Latin for seas): broad, smooth, lowland plains; the dark areas; vast solidified pools of ancient basaltic lava; evidence that the moon was once hot and active
Near side (left) and far side (right) of the Moon, by Lunar Reconnaissance Orbiter

7. Features of the Moon Rilles: long valleys
Craters: primarily impact craters formed by the continuous bombardment of the moon by meteorites
Estimated to be about 300,000 larger than 1km across
Named for scholars, scientists, artists and explorers; Copernicus is an example
Near side (left) and far side (right) of the Moon, by Lunar Reconnaissance Orbiter

8. Movements of the Moon
The Moon's orbit is inclined about 5 degrees from the Earth's ecliptic orbit around the sun.
One revolution takes about 27.3 days. (The Orbital speed of the moon is 3,680 km/h.)
One rotation of the moon on its axis takes about the same 27.3 days.
Because a revolution and a rotation take the same time, we always see the same side of the moon.

9. Movements of the Moon The orbit of the moon is elliptical.
Perigee: point closest to Earth; about 362,600 km
Apogee: point farthest from Earth; about 405,400km

10. Origin of the Moon The moon is about 4.5 billions years old
Formation:
One Theory: The moon formed far away from the Earth and was then “captured” by the Earth’s gravity.
Second Theory: The moon formed along with the Earth.
Third Theory: The moon split off from the Earth due to centrifugal force.
Each of these theories fails in some way to account for all the evidence we have.
Theory one – would require too great and atmosphere to dissipate the energy of the passing moon to capture it; also would not account for the similarity in composition.
Theory two: doesn’t explain the depletion of metallic iron in the moon
Theory three would require too much initial spin for the Earth
None account for the high angular momentum of the Earth-Moon system.

11. Origin of the Moon
Current Prevailing Theory: Soon after the Earth was formed, a Mars-sized asteroid impacted it and blasted material into orbit around the Earth. That material came together to form the moon.
Recent evidence (2012) suggests that this may not be correct, as the moon’s composition appears to be exactly the same as the Earth’s, with no second contributor.