Chapter 28: The Moon

Moons Are Natural Satellites Satellite – a body that orbits another body 7 planets in our solar system have smaller orbiting bodies Artificial satellites – satellites of Earth Space telescopes Weather data equipment

Moon Vocabulary – Mare (Maria) Latin for “sea” Large dark area of basalt on the moon Dark solidified lava Formed more than 3 billion years ago

Moon Vocabulary - Craters Bowl-shaped depressions Cover surface of moon Formed from leftover debris during solar system’s formation

Moon Vocab – Ridges and Rilles Long deep channels that run through maria Ridges Long narrow elevations of rock Rise out of surface Criss-cross maria

Moon Vocab - Regolith Layer of gas and dust Covers most of the lunar surface Formed from crushing of lunar rocks by meteorites

Lunar Rocks Similar to Earth rocks Igneous rocks Contains many of same elements Igneous rocks Rocks that form when magma cools

Sides of the Moon… Near Side Far Side Always faces Earth Always faces away

Lunar Layers 3 layers Crust Mantle Core Outer layer Beneath crust Thicker on Far Side 60-100 km thick Mantle Beneath crust Made of silica, magnesium, iron Core Small, made of iron Neither completely solid nor completely liquid Why Moon has almost no gravitational field

How Was the Moon Formed? Giant Impact Hypothesis Large Mars-sized object collided with Earth Over 4 billion years ago Chunks of Earth’s mantle ejected into orbit Debris eventually clumped together to form the Moon

Differentiation of Lunar Interior When Moon formed… Surface was covered by ocean of molten rock Over time: Denser material moved to center  formed core Less dense material cooled  formed crust

Meteorite Bombardment Meteorites had hit the Moon over time Bombardment decreased significantly 3 billion years ago Stopped all geologic activity on Moon Moon has looked the same since then

Other Minor Bodies Other satellites that orbit the Sun Leftover debris from formation of solar system Include Asteroids Meteoroids Meteorites Comets

Asteroids Fragments of rock and metal Largest of the minor bodies Orbit the Sun in ellipses Largest of the minor bodies Known as “minor planets” Largest asteroid in solar system: Ceres Other examples: Earth-grazers – pass within 2x distance to the Moon Trojan asteroids Located on either side of Jupiter

Meteoroids Called meteors when enter Earth’s atmosphere Small pieces of rock or metal in space Meters to millimeters in size

Meteorites Any part of a meteor that is left when it hits Earth 3 types: Stony Iron Stony-Iron

Comets Bodies of rock, metals, gases, and ice 3 major parts of a comet Orbit the Sun Long period – orbit lasts longer than 100 years Short period – orbit lasts shorter than 100 years 3 major parts of a comet Nucleus  core Coma  spherical cloud of gas and dust around core Tail evaporating gas and dust Faces away from Sun

Comets, Cont’d Originate in the Oort Cloud Spherical cloud of gas and dust Lies beyond Pluto’s orbit Contains nuclei of billions of comets