Earth’s Moon

1. Earth’s Moon Lesson 4, Chapter 1

2. The Moon’s Surface • In 1609, the Italian scientists Galileo Galilei heard about a telescope, and soon made his own. He was able to see more detail than anyone had ever seen before. • Features on the moon’s surface include maria, craters, and highlands.

3. Maria and Craters • The moon’s surface has dark, flat areas, which Galileo called maria, the Latin word for “seas.” • The maria area actually hardened rock formed from huge lava flows that occurred between 3 and 4 billion years ago. • The moon is also marked by large round pits called craters. For a long time scientists believed these craters were formed by volcanoes, but they were actually caused by meteroids.

4. Highlands • Galileo correctly inferred that some of the light colored features he saw on the moon’s surface were highlands, or mountains. • The rugged lunar highlands cover much of the moon’s surface.

5. Characteristics of the Moon • The moon is dry and airless. Compared to Earth, the moon is small and has large variations in its surface temperature. • The moon is 3,476 kilometers in diameter, a little less than the distance across the United states. • On the moon’s surface, temperature ranges from a torrid 130 C in direct sunlight to a frigid -180 C at night. • The moon’s surface gravity is so weak that gases can easily escape into space. • The moon has no liquid water. However, there is evidence that there may be large patches of ice near the moon’s poles.

6. The origin of the moon • Scientists theorize that a planet-sized object collided with Earth to form the moon. • This is known as the collision theory which happened about 4.5 billion years ago when the Earth was very young. • 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.