Basics

Maria (Seas) - dark volcanic plains (lowland) made of dense rock (mafic = magnesium,

iron)

Highlands - light regions made of less dense rock (felsic = silicon, oxygen, potassium)

Regolith - covers all surface areas. Fine-grained debris from asteroid impacts.

Differentiation

Process during planet/moon formation.

Molten (liquid) rock allows denser materials to sink to form mantle and core…less dense material rises to form crust.

Moon has core, mantle, crust… like Earth.

Formation

Key Facts to Reconcile:

1. Moon is composed of same materials as Earth…

2. Small core…not much iron or other dense materials.

3. Rotation - the angular momentum or spin of the earth-moon system.

Capture Theory

Capture Theory - Earth captured a roving planetoid/asteroid…

Problems

1. Moon would be composed of different materials.

2. Moon too large for Earth’s gravity to catch it.

Fission Theory

Fission Theory - Fast spinning Earth expelled piece (Pacific Ocean?)…

Problems

1. Oceanic rock is young... Moon is old.

2. Moon would orbit on same plane as earth.

Co-Formation Theory

Co-Formation Theory - Formed at same time…

Problems

1. Moon formed about 100 million years after Earth.

2. Would have bigger core and more iron.

The Moon

Formation - Impact from Mars-size object ejects material into orbit… forms Moon.

- Best model to explain Moon’s composition.

http://www.space.com/14908-moon-evolved-video-guided-tour.html

Lunar Phases

Half of the Moon is always illuminated by the Sun.

But, we see moon phases? Why?

-- Because of moon’s rotation, revolution, and angle.

Lunar Phases

Moon revolves around Earth in 27.3 days

Moon rotates around its axis in 27.3 days

-- Because of this, we only see one side of moon.

(synchronous orbit).

But,

A full phase cycle = 29.5 days.

Why the 2 day difference?

Because the Earth has moved in the meantime

Moon Phases

Terms:

Waxing = moon is in first half of cycle.

Waning = moon is in last half of cycle.

Gibbous = “hunchback” = moon close to full.

Eclipses

Lunar Eclipse = when Earth’s shadow covers the moon.

Only during full moon phase.

Umbra (shadow) covers moon completely. All persons on dark side of Earth can see the eclipse.

Usually 2 to 5x per year.

Solar Eclipse

Solar Eclipse = When the moon covers the sun.

Only during a New Moon.

Umbra (shadow) is small. Covers only a small portion of Earth.

Usually 2 to 5x per year.

Moon’s Orbit

The Moon’s orbit is tilted 5o. Important!

Otherwise, there would be a solar and lunar eclipse every month.

Moon’s Orbit

Tides

Tides = cyclic rise and fall of ocean levels.

Caused primarily by Moon’s gravity.. not sun’s.

Spring Tide = Moon and Sun align.

Neap Tide = Moon and Sun not aligned.

Neap vs. Spring Tides

Spring Tides:

- highest high tide and lowest low tide.

- Happens at full and new moon phases.

Neap vs. Spring Tides

Neap Tides:

- High tide not so high and low tide not so low.

- Happens at quarter moon phases.