1. Ch. 30.1 The Earth’s Moon

2.  Satellite—a body that orbits a larger body.  The moon is earth’s natural satellite.  The moon has weaker gravity (1/6 th that of earth) because it has less mass than earth.  Moon’s gravity too weak to hold gasses, so no atmosphere.

3.  Moon’s temp. ranges from 134 C during the day to -170 C at night.  Moon rotates once every 27.3 days, but a lunar day is 29.5 earth days because the moon is also travelling around the sun at the same time.

5. The Lunar Surface  Observers from earth see light and dark patches.  Light areas are called highlands, and consist of light-colored rock.  Dark areas are called maria (latin for seas) and are smooth and reflect little light. Made of dark solidified lava, from ancient volcanic eruptions.

8.  Rilles are long deep channels that run through the maria. Probably lava channels.

10. Craters  Cover moon’s surface. Most formed about 4 billion years ago.  Object striking moon leaves bowl- shaped depression. Displaced material settles out in streaks, called rays.  Since no erosion on the moon, its surface has changed little since it formed.

13. Lunar Rocks  Much of moon’s surface crushed into dust and fragments by meteorite impacts.  Regolith—the layer of dust and fragments (1 m to 6 m) that covers the lunar surface.  Surface lunar rocks composed mainly of oxygen and silicon.

14.  Highland rocks are light-colored, course-grained anorthosites, rich in calcium and aluminum.  Maria rocks are fine-grained, dark colored basalts, high in titanium, iron, and magnesium.  Breccia—fragments of other rocks melted together after meteorite impacts. Common all over.

16. The Interior of the Moon  Info from seismographs placed by Apollo astronauts.  Weak moonquakes recorded.  Crust is 60 to 100 km thick.  Underneath is denser mantle, to a depth of about 1000 km.  Possibly slightly molten or small iron core. Almost no magnetic field.

18. Development of the Moon  Giant-impact hypothesis– Mars-sized object struck the earth and ejected fragments into orbit, which eventually joined to form the moon.  2 nd Stage—surface of moon covered by ocean of molten rock. Denser parts separated and sank to the core.

20.  3 rd Stage—surface cooled to form crust. Meteorites struck and broke through, causing molten rock to flow up and form the smooth maria.  About 3 billion years ago, impact activity decreased, and geologic activity stopped due to cooling. Rayed craters formed by most recent impacts.