Chapter 28 Minor Bodies of

the Solar System

The Moon

The moon is a natural satelliteA satellite is a natural or artificial body that revolves around a celestial objectSputnik, was launched by the Soviet Union the month I was born!

It was the first artificial satellite

Apollo program

1969-19726 spacecraft to the moon

July 20, 1969 Neil Armstrong set foot on the moon.

Do you know what he said?That’s one small step for man, one giant leap for mankind.

Moon gravity

The moon has much less mass so has much less gravityA person weighs 1/6th the amount he weighs on Earth

Lunar surfaceLunar comes from the Latin word luna moonLight and dark patches visible

Light—anorthositesDark—maria—seas of solidified lava formed from massive meteoroid bombardment

Regolith

The surface of the moon is covered with a fine dust called regolith2 causes:

Meteor bombardmentThermal shock—expansion and contraction caused by lack of an atmosphere

One side of the moon always faces Earth

The pull of the Earth’s gravity during formation caused the crust on the far side to become thicker

Near side lunar crust is 60km thickFar side up to 100 km thick

One Side of the MoonWe always see the same side because the Moon’s rotational rate matches the rate at which it revolves around the Earth.Rotates (and revolves) once every 27.3 days.Gravity lock between the Earth and the Moon

So why is a lunar cycle 29.5 days?

While the moon is revolving around the Earth, Earth and the Moon are also revolving around the sunIt takes time to catch up to Earth’s movement

BarycenterThe Earth and the moon actually revolve around each other.Their common center of mass is called the barycenterIt is located within the Earth

READ PGS 725 & 732

Layered

Crust MantleMaybe a small iron core (layered)No magnetic field

Tides Because of the pull from the moon’s gravity on Earth's water, the water forms a bulge on the moon-ward side. This is high tide.

The position of the moon determines the type of tide

Formation of the MoonFormerly several main hypotheses

Now . . .

The Giant Impact HypothesisA Mars-sized body hit the Earth while it was still quite hotThe collision ejected chucks of mantle into orbit around EarthThis came together to form the moon

Other Theories of the Moon’s formation

Simultaneous creationFissionCaptureCollision

Simultaneous creation

Formed at the same time from same stuffProblem: Earth has 3 X's more iron

Fission

George Darwin, son of Charles,

hypothesized that the Moon and Earth were originally one body.As it revolved and rotated it cooled and began to rotate faster A giant bubble of still molten material pulled away and escaped

Capture

Formed elsewhere in the solar system and was caught as it traveled by the Earth

CollisionYoung Earth was hit by an asteroid that knocked off a chunk and then the asteroid and chunk were caught in the gravitational field.

One Side of the MoonWe always see the same side because the Moon’s rotational rate matches the rate at which it revolves around the Earth.Rotates (and revolves) once every 27 days.Gravity lock between the Earth and the Moon

Misc Factoids

Diameter about the size from San Francisco to New York City1996 discovered ice deposits at the poles

Phases of the Moon

At any given moment rays of sunlight illuminate one half of the Moon's surface. Because the moon rotates and revolves around earth we see phases--changes in shape that occur every month.

Study this picture page730!!!!!!!

New moon--

occurs when the Sun, moon and Earth are lined upThe new moon is the side we cannot see

Full moon--we see the side that is lit up

Waxing--getting biggerright side lit up

Waning--getting smaller left side lit up

Crescent-- Crescent roll shape

Half moon—1st quarter

Gibbous--More than half is lit upFunny name for a funny shape

We put these words together to describe the moon.

Full moonNew moonWaxing gibbousWaning crescent

Phase Game

SU

NL

IG

H T

Full Moon

1st QTR

Waxing Gibbous

Waxing Crescent

New Moon

Waning Gibbous

3rd QTR

Waning Crescent

Earth

Dusk

Midnight Noon

Dawn

EclipsesThe Sun is 400 times larger than the Moon in diameter, it is also 400 times farther away. So, the sun and Moon appear the same size in the sky. This allows us to have eclipses.

Moon is between the sun and earth

Solar eclipse

Moon's shadow falls on the Earth

Who gets to see them???

The shadow has two parts,

the umbra and penumbraUmbra--darker, inner

shadowPenumbra– lighter, outer shadow

Lunar eclipse

Earth's shadow falls on the moon

Why are eclipses so rare?

5.2 tilt of the moon orbital plane

The Earth and Moon have different orbital planes