19.4 Earth’s Moon
Learning Target:
I can describe features found on the moon’s surface.
Use your textbook, pages 680-681, to complete the following notes:
Introduction
 Galileo made a telescope by putting two lenses in a wooden tube. This tool made distant
objects seem closer.
 Galileo pointed his telescope at the moon and saw that it was not a perfect sphere - the
moon has an irregular surface with a variety of features.
The Moon’s Surface
 Features on the moon’s surface include maria, craters, and highlands.
 Maria are the dark, flat areas on the moon’s surface. Galileo thought they were
oceans, but they are hardened lava formed from huge lava flows 3-4 billion years
ago.
 Craters are large round pits on the moon’s surface. Many scientists thought they
had been made by volcanoes. Now they know they were caused by the impacts of
meteoroids (chunks of rocks or dust from space). Since the moon has no liquid
water or atmosphere, its surface has changed little for billions of years.
 Highlands are mountains on the moon. Galileo inferred these were mountains
because the peaks cast dark shadows like the rims of the craters. The rugged
highlands cover much of the moon’s surface.
Answer the following questions using your notes or your textbook:
1) A scientific instrument that makes faraway objects appear closer is a telescope.
2) Match each term with its meaning:
1. Maria a
a. large, round pits on the moon
2. Craters a
b. dark, flat areas on the moon
3. Highlands d
c. chunks of rock or dust from space
4. Meteoroids c
d. mountains on the moon
3) Which moon feature was caused by meteoroids? craters
4) Which moon’s feature is linked to ancient volcanic activity? maria
5) Which moon’s feature cast dark shadows? highlands
Learning Target:
I can identify some characteristics of the moon and explain how the moon formed.
Use your textbook, pages 682-683, to complete the following notes:
Characteristics of the Moon
The moon is about 384,000 km from the Earth. The moon is dry and airless. Compared to
Earth, the moon is small and has large variations in its surface temperature.
Size and Density
 The moon is 3,476 km in diameter (a little less than the distance across the United
States).
 Although the moon is about ¼ the Earth’s diameter, it only has 1/80 its mass.
 The moon’s average density is similar to the density of Earth’s outer layers.
Temperature and Atmosphere
 On the moon’s surface, temperatures range from 130oC in direct sunlight to -180oC at
night.
 Temperatures vary so much because the moon has no atmosphere.
 The moon’s surface gravity is so weak that gases can easily escape into space.
Water
 The moon has no liquid water.
 There is evidence that there may be large patches of ice near the moon’s poles.
The Origin of the Moon
 The theory of the moon’s origin that best fits the evidence is called the collision-ring
theory.
 Billions of years ago, big rocks were moving around in space.
 Scientists theorize that a planet-sized object collided with Earth to form the moon.
Material from the object and Earth’s outer layers was ejected into orbit around Earth,
where it formed a ring.
 Gravity caused this material to combine to form the moon.
Answer the following questions using your notes or your textbook:
1) The moon is about ¼ diameter of Earth.
2) Why do temperatures vary so much on the moon’s surface? No atmosphere
3) Briefly describe the most widely accepted theory of the moon’s origin. The collisionring theory – a planet-sized object hit earth and it was ejected into orbit around Earth
where it formed a ring. Gravity pulled the object together to form the moon.