1. Our Moon and Earth System

2. The Moon – Our Nearest Neighbor
A natural satellite
One of more than 96 moons in our Solar System
The only moon of the planet Earth

3. Location, Location, Location!
About 384,000 km (240,000 miles) from Earth
3,468 km (2,155 miles) in diameter (about ¼ the size of Earth)

4. Birth of Our Moon “Born” 4-5 billion years ago
Formed from impact of Mars-sized “planetesimal” on Earth
Moon’s rocks are very similar to those on the Earth

5. Moon’s Interior 3 major divisions of the Lunar interior
Crust - average thickness of about 70 kilometers
Mantle
Core - radius is between 300 and 425 kilometers

6. The Moon’s Surface No atmosphere No liquid water Extreme temperatures
Daytime = 130C (265°F)
Nighttime = -190C (-310 F)
1/6 Earth’s gravity

7. Lunar Features - Highlands
Rilles
Highlands are the lighter part of the moon
Mountains up to 7500 m (25,000 ft) tall
Rilles (trenchlike valleys)

8. Lunar Features - Maria
Originally thought to be “seas” by early astronomers
Darkest parts of lunar landscape
Filled by lava after crash of huge meteorites on lunar surface 3-4 billion years ago
Mostly basalt rock

9. Lunar Features - Craters
Up to 2500 km (1,553 miles) across
Most formed by meteorite impact on the Moon

10. Movements of the Moon
Revolution – Moon orbits the Earth every 271/3 days
The moon rises in the east and sets in the west
The moon rises and sets 50 minutes later each day
Rotation – Moon turns on its axis every 27 days
Same side of Moon always faces Earth

11. Far Side of the Moon First seen by Luna 3 Russian space probe in 1959
Surface features different from near side
More craters
Very few maria
Thicker crust

12. It’s Just a Phase Moonlight is reflected sunlight
Half the moon’s surface is always reflecting light
From Earth we see different amounts of the Moon’s lit surface
The amount seen is called a “phase”

13. FOUR MAIN SHAPES
FULL
CRESCENT
GIBBOUS
QUARTER

15. Tides Moon affects Earth by the formation of tides
Moon’s gravity pulls on Earth along imaginary line connecting Earth and the Moon that creates bulges of ocean water on both the near and far sides of the Earth
Earth’s rotation contributes to tide formation
As Earth rotates, these bulges align with the Moon
Person at shoreline on Earth’s surface would see ocean level rise every 12 hours

16. Spring and Neap Tides
Sun’s gravitational effect (about ½ of the Moon’s) not as strong as the Moon’s because further away from the Earth
When Sun and Moon are aligned, see stronger tides because effects are combined
These higher tides are called spring tides and they are high when Moon is nearest Earth and Earth is nearest the Sun
Lower than normal tides, or neap tides, occur when the Moon is at a right angle to the Sun-Earth line

17. Nutation
In addition to causing tides, the moon’s orbit around Earth also causes the Earth to nod, or bob throughout its rotational period, called nutation

18. Solar Eclipse
Solar eclipse occurs when the Moon passes directly between the Sun and the Earth and blocks our view of the Sun
When the Moon perfectly blocks out the Sun’s disk, we only see the dim, gaseous outer layers of the Sun; this is called a total solar eclipse
Partial solar eclipse seen when the Moon blocks a portion of the Sun’s disk

19. Solar Eclipse
The difference between a partial and total solar eclipse can be explained by the fact that the Moon casts a shadow on Earth
Shadow consists of two regions: inner portion called the umbra that doesn’t receive direct sunlight, and an outer portion called the penumbra that receives some sunlight

20. Solar Eclipse
People who witness eclipse from the umbra (inner portion) see a total solar eclipse
People who witness eclipse from the pnumbra (outer portion) see a partial solar ecipse
Umbral shadow very small (~270 km), so total solar eclipse visible from small portion of Earth

21. Only when the Moon intersects the Earth;s ecliptic in line with the Sun and Earth does a solar eclipse occur
Closest point in Moon’s orbit around Earth is called the perigee
Farthest point in Moon’s orbit around the Earth is the apogee
Effects of Orbits

22. Effects of Orbits
When Moon is near apogee, appears smaller from Earth and can’t block out Sun entirely
When Moon is near perigee, appears larger on Earth and can block out Sun entirely

23. Lunar Eclipse
Lunar eclipse occurs when Moon passes through Earth’s shadow
Can only happen during a full moon when the Moon is in the opposite direction from the Sun
Earth has two parts to its shadow like the moon: umbral and penumbral
When entire Moon is in the Earth’s umbral shadow, you can see a total lunar eclipse

24. Lunar Eclipse
Total lunar eclipse lasts approximately 2 hours; can see a Moon during this phase because sunlight that has passed near Earth has been refracted by Earth’s atmosphere
Gives light a reddish appearance

25. Periodicity of Eclipses
Solar and lunar eclipses don’t occur every full moon because the Moon in orbit usually passes above or below the Sun as seen from Earth
Solar and lunar eclipses occur in almost equal numbers, with slightly more lunar eclipses
Maximum number of combined eclipses that can occur per year is seven; this won’t happen again until 2038

26. What would you need to live there?
Moon base of the future?
What would you need to live there?