Moons Features and Phases Chapter 28

General Information Satellite: a body that orbits a larger body. Seven planets in our solar system have smaller bodies that orbit around them. Moons: natural satellites Now, thousands of artificial satellites that orbit around earth-weather data, space telescopes, etc.

Mare Mare : large, dark area of basalt on the moon; plains of dark, solidified lava. (Maria) Latin for “sea” Latin for “sea” Formed more than 3 billion years ago Formed more than 3 billion years ago

Craters Most of the surface of the moon is covered with numerous bowl-shaped depressions, called craters. Most formed from leftover debris from formation of solar system 4 billion years ago. Most formed from leftover debris from formation of solar system 4 billion years ago.

Rilles and Ridges Rilles : long, deep channels that run through the maria. Leftover lava channels from formation of maria Leftover lava channels from formation of maria Ridges : long, narrow elevations of rock that rise out of the surface and criss-cross the maria

Regolith Regolith : layer of gas and dust that covers most of the lunar surface. Formed from the crushing of lunar rocks by meteorites. Formed from the crushing of lunar rocks by meteorites.

Lunar Rocks Similar to rocks on earth Contain many of same elements as earth rocks Igneous-rock that forms when magma cools

The three layers of the moon The side of the moon that always faces the Earth is called the NEAR SIDE. The other side that faces away is called the FAR SIDE. Moon’s crust on far side is thicker than that of near side due to pull of earth’s gravity Km thick

Moon’s mantle and core Mantle : beneath the moon’s crust; made of silica, magnesium, and iron. Makes up more than half of the distance of the moon’s diameter Makes up more than half of the distance of the moon’s diameter Core : small iron core that has radius less than 700 Km. Thought neither to be completely solid or completely liquid  explain why moon has almost no overall magnetic field Thought neither to be completely solid or completely liquid  explain why moon has almost no overall magnetic field

The Giant Impact Hypothesis Began when large object, size of Mars, collided with Earth more than 4 billion years ago. Chunks of Earth’s mantle ejected into orbit around Earth. Debris eventually clumped together to form moon

Differentiation of Lunar Interior Early, lunar surface was covered by an ocean of molten rock. Over time, densest materials moved toward the center of the moon and formed small core and least dense materials formed the outer crust.

Meteorite Bombardment Outer surface of the moon eventually cooled to form a thick, solid crust over the molten interior. Meteorite bombardment decreased significantly about 3 billion years ago and, thus, virtually ally geologic activity stopped. This explains why the moon looks today almost exactly as it did 3 billion years ago.

Phases & Cycling The moon revolves around the Earth in 27.3 days It takes 29.5 days to go through a complete cycle of phases. (New moon to new moon) Lunar eclipse = Occurs when Earth is between the moon and the sun (earth’s shadow)