The three main hypotheses for the origin of the moon are that it was either 1) a small planet captured by Earth's gravity, 2) formed alongside Earth from the same dust and gas cloud, or 3) ripped away from the Earth as a bulge when the young Earth spun faster. The moon has dark lava plains called maria, ancient highlands made of different rock, and many circular craters from impacts. It rotates in sync with its orbit around Earth, always keeping the same face toward our planet and exhibiting phases from new to full.

1. Our moon

2. THE ORIGIN OF THE MOON
3 hypothesis:
1. The moon was originally a small planet orbiting the Sun that
approached the Earth and was captured by its gravity
2. The Moon and Earth were “twins,” forming side by side from a
common cloud of dust and gas
3. The young Earth initially spun enormously faster than now and
formed a bulge that ripped away from the Earth to become
the moon

6. SURFACE FEATURES

12. Maria – basalt, a dark congealed lava rich in iron, magnesium and
titanium silicates
- Mare rocks are about 3.1-3.9 billion years old
Highlands – rich in calcium and aluminum silicates based on rock
samples collected by lunar astronauts
- less dense than mare rock and considerable older (about 4-4.4
billion years
Craters – rugged pits with large number of circular features
- made by impacts of solid bodies striking the Moon

13. Rays – light streaks radiating outward from many craters

14. Rilles – lunar canyons carved by ancient lava flows

15. MOON’S ROTATION AND ORBIT
Synchronous rotation – the Moon does turn on its axis relative to
the stars, but with a rotation period exactly equal to its orbital
period
- it keeps one face toward the planet

16. PHASES OF THE MOON