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Chapter 24 – Earth’s Moon Ms. Martel Getting to the Moon • Getting a spacecraft to the moon is a complex task. – The rocket used must be large enough to put the spacecraft into Earth’s orbit before the rocket stops firing. – Once the spacecraft is in Earth’s orbit, another rocket fires toward the point where the moon will be when the spacecraft gets there. – The aiming and firing must be precise, otherwise the spacecraft will miss the moon and go into orbit around the sun. The First Spacecraft to the Moon • The first spacecraft to leave Earth orbit and reach lunar orbit was part of the Luna series launched by the former Soviet Union. • The United States launched the Pioneer series at the same time, however, their first attempts were unsuccessful. • In 1961, President Kennedy made it a national goal to land an astronaut on the moon and return them safely to Earth. Mercury and Gemini • The first American spacecraft to carry an astronaut was the Mercury Series. The series had 9 different space shuttles that were used to practice orbiting ships around the Earth. • The Gemini spacecrafts were designed for two astronauts. – These spacecrafts had two purposes: • First was to find out if humans could survive and work in the weightlessness of space for the 10 days needed to go to the moon and back. • The second was to train astronauts to maneuver the spacecraft. Apollo • The Apollo missions accomplished President Kennedy’s objectives. • In 1969, Apollo 11 astronaut Neil Armstrong and Edwin Aldrin Jr became the first people to walk on the moon. • The Apollo astronauts brought back a total of 380 kg of rock and soil samples. • They left behind instruments to measure things such as moonquakes, magnetic field, solar wind particles etc. The Space Shuttle • Unlike its predecessors Mercury, Gemini, and Apollo, the versitile space shuttle is designed to be reused. Each shuttle has 3 main units: – The orbiter, or the airplane body – The external tank, which feeds propellants to the engine during the first stage of flight. – Two solid rocket boosters that provide the energy to the initial lift-off. These are discarded about 10 mins after the launch. Properties of the Moon • The moon’s diameter is 3476 km, or more than one fourth Earth’s diameter. • The moon’s low gravity and low escape velocity means its much easier to launch a spacecraft from the moon than from Earth. • The equipment left over from the Apollo aircraft continued to operate for 8 years, and recorded enough data for scientists to develop a model of the moon’s interior. – The moon just like Earth has a layered structure. The Origin and History of the Moon • One likely theory based on lunar data proposes that the moon formed about 4.6 billion years ago from a collision between Earth and a Mars-sized object. – In theory, the collision broke through the solid crust and splashed a huge mass of molten rock into space, which cooled and became to moon. – Then, showers of rock-like particles bombarded the moon’s surface. This bombardment lasted for hundred of millions of years. – Hot lava then poured out of gaps in the great basins. These eruptions continued for nearly a billion years. – Finally the moons became geologically inactive, this has been the case for 3 billion years. Lunar Rocks: Evidence of the Moon’s History • Lunar rocks differ from Earth’s in several ways. Lunar rocks contain no water at all. • They contain more elements with high melting points such as titanium, rather than gas elements such as nitrogen. • Radioactive dating has been used to find the age of lunar rocks. Most are between 4-4.3 byo, however the oldest ones are dated at 4.6 byo. • The Lunar Maria Galileo thought the dark spot on the moon were seas, and thus called them Lunar Maria (the Latin word for seas). • However there is no signs that indicate the moon ever had water. – The Maria are smooth plains with huge circular basins. – The first spacecraft's to circle the moon found that the moon’s gravity was greater over some of the more circular maria. – These areas of higher gravity are called mascons for “mass concentrations.” – Rilles are long deep clefts or cracks running through maria bedrock. The Lunar Highlands • The final 3 Apollo flights landed in lunar highlands. These areas appear brighter than the maria because their rocks are lighter and reflect more sunlight. • Lunar scientists believe that the lunar highlands were thrown up by impact craters. Lunar Soil • Lunar soil is not really soil. – Scientists prefer t call it regolith, which means loose rock materials. – Unlike Earth soil, regolith contains no water or organic material. – Regolith was made by the smashing impact of meteoroids of all sizes. The Moon’s Orbit • The moon revolves around the Earth from west to east in an elliptical orbit. • It takes 27 1/3 days to revolve around the Earth. • The sun’s diameter is nearly 400 times the moon’s diameter, yet they both appear to be about the same size in the sky. – The reason is that the sun is nearly 400 times farter away from Earth than the moon. Moonrise and Moonset • The moon rises in the east and sets in the west, like the sun’s rising and setting. – As the moon moves around Earth, it can be seen rising at a different time each night. – The moon moves about 13° eastward along its orbit every day. Thus the Earth must rotate an extra 13° more than 360° to see the moon rise each night. – This takes approximately 50 minutes, which means the moon rises about 50 minutes later each day and sets about 50 minutes later as well. The Moon’s Phases • The phases of the moon are the daily changes in the moon’s appearance. • This occurs for two reasons: – 1. the moon is seen by reflected sunlight. – 2. the moon is in orbit around Earth. • 1) New Moon • 2) Waxing Crescent • 3) Waxing Quarter • 4) Waxing Gibbous • 5) Full Moon • 6) Waning Gibbous • 7) Waning Quarter • 8) Waning Crescent Lunar Eclipses • The shadow cast by any opaque object has two parts: – The umbra is the total shadow – The penumbra is the partial shadow surrounding the umbra. • The lunar eclipse can occur only at the full moon phase • The moon remains visible during its eclipse, but it has a dusky red or coppery colour. • On the average, at least one total lunar eclipse occurs every year. Solar Eclipse • A solar eclipse occurs when the moon’s umbra reaches Earth’s surface, and can only occur during the new moon. • Locations on Earth within the umbra experience a total solar eclipse – At that time, the moon blocks the entire photosphere of the sun. The sky is dark, bright stars and planets can be seen with the unaided eye. The Moon and Tides • The daily rise and fall of the ocean waters are called tides. • Tides are unusually large during the new moon and full moon phases, and unusually small during quarter moon phases. • Sir Isaac Newton first explained how the gravity of the moon causes tides. Spring and Neap Tides • The sun has the same kind of effect on Earth’s water’s as does the moon. – However, because the sun is so much farther away, the sun’s effects are only half that of the moons. – At new moon and full moon, we have spring tides, where high tides are especially high and low tides are especially low. – At quarter phases of the moon, we have neap tides, where high tides are not very high and low tides are not very low.