CHAPTER 25 EARTH’S MOON

25.1 ORIGIN AND PROPERTIES OF

THE MOON

DAHS MR. SWEET

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OBJECTIVES

• EXPLAIN VARIOUS HYPOTHESES ABOUT HOW THE MOON FORMED.

• DESCRIBE THE FEATURES AND PROPERTIES OF THE MOON.

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WHAT IS THE MOON?

• A NATURAL SATELLITE• ONE OF MORE THAN 96

MOONS IN OUR SOLAR SYSTEM

• THE ONLY MOON OF THE PLANET EARTH

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ORIGIN OF THE MOON

• SCIENTIST BELIEVE THE MOON FORMED WHEN A LARGE OBJECT ABOUT THE SIZE OF A PLANET HIT EARTH.

1. Earth is hit off-center by a planet-sized object.

2. The impact heats and deforms both bodies. Some rocky debris remains in orbit around Earth.

3. The debris ring, made of rock from the outer layer of both objects, gradually coalesces, forming the moon.

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DEVELOPMENT OF THE MOON

• METEOROID IMPACTS MELTED MOONS SURFACE AND CREATED CRATERS

• FORMED MAGMA OCEAN• LIGHTER MATERIALS ROSE TO SURFACE –

COOLED AND HARDENED• 4.0 – 3.5 BILLION YEARS AGO IMPACTS

DECREASED• OVER MILLIONS OF YEARS MAGMA RICH IN

IRON ERUPTED FILLING LARGE BASINS CREATING MARIA

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Observe images illustrating the impact theory of the moon's formation.

YouTube - How the Moon was born!

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MOON TODAY

• CORE INACTIVE

• IMPACTS FROM MICROMETEOROIDS CONTINUE TO CHANGE SURFACE THROUGH IMPACTS AND EROSION

• MOON HAS NO ATMOSPHERE TO BURN THEM UP

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LAYERS OF THE MOON

Iron Core

Near side crust (about 65 km thick)

Mantle

Far side crust (about 150km thick)

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UPDATE

• National Geographic Moon

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PROPERTIES AND FEATURES OF THE MOON

• SAME SIDE OF THE MOON FACES EARTH - GEOSYNCHRONOUS ORBIT

• ABOUT 384,000 km (240,000 mi.) FROM EARTH

• 3,476 km (2,155 miles) IN DIAMETER – ABOUT ¼ THE SIZE OF

EARTH

• DENSITY 3.3g/cm3

• 1/6 EARTH’S GRAVITY

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FAR SIDE OF THE MOON

• FIRST SEEN BY THE LUNA 3 RUSSIAN SPACE PROBE IN 1959

• SURFACE FEATURES ARE DIFFERENT FROM THE NEAR SIDE– MORE CRATERS– VERY FEW MARIA– THICKER CRUST

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THE MOON’S SURFACE

• NO ATHMOSPHERE• NO LIQUID WATER• EXTREME TEMPS.

– DAYTIME = 130C (265°F)

– NIGHTIME = -190C (-310 F)

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MARIA

• ORIGINALLY THOUGHT TO BE “SEAS” BY EARLY ASTRONOMERS

• DARKEST PARTS OF THE LUNAR LANDSCAPE

• MOSTLY BASALT ROCK MADE OF FELDSPARS AND PYROXENE

• YOUNGEST ROCKS

Maria

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MASCONS

• MASCONS MEANS MASS CONCENTRATIONS

• AREAS IN MARIA WITH– HIGHER DENSITY ROCKS– HIGHER GRAVITY READINGS

• DISCOVERED IN 1960’S

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RILLES

• TRENCHLIKE VALLEYS RUNNING THROUGH MARIA

• MAY HAVE FORMED FROM A RIVER OF LAVA

• THE RIVER SURFACE HARDENED

• THE LAVA DRAINED AWAY

• THE SURFACE COLLAPSED

RILLE

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HIGHLANDS

• MOUNTAINS UP TO 7,500 m (25,000 ft) TALL• THOUGHT TO BE THE ORIGINAL CRUST• FORMED FROM IMPACTS• LIGHTER IN COLOR THAN MARIA• ROCK SAMPLES SIMILAR TO GABBRO AND

BRECCIA– ROCKS MADE OF ANGULAR FRAGMENTS– IMPACTS MELTED ROCKS TOGETHER

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CRATERS

• CIRCULAR HOLLOWS FORMED BY METEOR IMPACTS

• SIZE RANGE IS MICROSCOPIC TO 2100 km DIAMETER

• MOST NAMED AFTER PEOPLE

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RAYS

• CONSIST OF SHATTERED ROCK AND DUST

• SPLASHED OUT BY METEROID IMPACTS

• COPERNICUS IS 93 km CRATER WITH RAYS 100’S km LONG

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LUNAR SOIL

• REGOLITH– LOOSE ROCK MATERIALS

• RANGE FROM FINE DUST TO SAND GRAINS 2 – 20 m DEEP

• CONTAIN NO WATER OR ORGANICS• FORMEDY BY SMASHING IMPACTS OF

METEORS• COMPOSED OF

– ROCK AND MINERALS CHIPS– GLASSY BEADS

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How did this spherule come to be on the Moon?

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Explanation: When a meteorite strikes the Moon, the energy of the impact melts some of the splattering rock,

a fraction of which might cool into tiny glass beads. Many of these glass beads were present in lunar soil samples returned to Earth by the

Apollo missions. Pictured above is one such glass spherule that measures only a quarter of a millimeter

across. This spherule is particularly interesting because it has been victim to an even smaller impact. A miniature

crater is visible on the upper left, surrounded by a fragmented area caused by the shockwaves of the small impact. By dating many of these impacts, astronomers

can estimate the history of cratering on our Moon.

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25.1 SECTION REVIEW

• PAGE 560

• 1-2 WITH QUESTIONS

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