Exploring the Moon • satellite (moon) - a natural or artificial body that revolves around planet and that has less mass than the planet does. • Seven of the planets in our solar system have natural satellites, or moons. Our moon is Earth’s satellite.
Lunar ExplorationMoon is 386,000 kilometers from EarthSpacecraft going to moon must: 1. Rocket large enough to put spacecraft into Earth’s orbit before rocket stops firing(burnout).2. Second rocket to fire out of Earth’s orbit toward moon.3. Precise firing of 2nd rocket in order not to miss moon and go into orbit around sun.
First Spacecraft to Moon • Jan. 2, 1959 - Luna 1 – first successful flyby of the moon • Sept. 12, 1959, the USSR became the first country to place an object on the moon when it struck the lunar surface with Luna 2. • On Oct. 4, 1959, it launched Luna 3, which took the first photographs of the far side of the moon before entering a highly elliptical orbit around the earth. • Between the summer of 1958 and December 1960, US made 8 attempts to fly by or orbit the moon with Pioneer-type spacecraft, none of which came close enough to make scientific measurements. • The first U.S. space probe to escape the earth's gravity was Pioneer 4, launched on March 3, 1959. • In 1961 President Kennedy made it a national goal to land an astrounaut on the moon and return safely. • From 1962 through 1963 NASA launched a series of six Ranger spacecraft to the moon in vain attempts to take close-up photographs of the lunar surface. Finally, between July 1964 and March 1965, Rangers 7, 8, and 9 took thousands of photographs.
Lunar Orbits • On April 3, 1966, the Soviets' Luna 10 became the first probe to successfully orbit the moon. • NASA's Lunar Orbiter program was designed to photograph possible sites for the Apollo landing missions. • Lunar Orbiter 1 was launched on Aug. 10, 1966, and entered into orbit around the moon on August 14. On the spacecraft's 26th orbit of the moon, the first pictures were taken, developed, and stored. Electronic scanning and transmission to earth commenced on August 18. It was confirmed that the moon is slightly pear-shaped, bulging approximately 0.4 km (0.25 mi) at its north pole. • While Lunar Orbiter 1 was sending photographs of the moon back to earth, the Soviets launched Luna 11 on Aug. 24, 1966.. Luna 12 followed on October 22, achieving lunar orbit. • On Nov. 6, 1966, the 386-kg (851-lb) Lunar Orbiter 2 headed for the moon and on the 10th was successfully put into a 196 to 1,850 km (122 to 1,150 mi) lunar orbit. There were many excellent pictures that were returned of the surface of the moon, particularly of potential Apollo landing sites. • Lunar Orbiter 3, launched on Feb. 5, 1967, entered lunar orbit on the 8th and soon began sending photographs. The primary mission of this probe was to photograph possible landing sites for Apollo astronauts, particularly the prime site in eastern Mare Tranquillitatis. It drew great attention on February 21 by photographing the Surveyor 1 spacecraft.
Examining the Surface of the Moon • The US succeeded in making a soft landing on the moon. Surveyor 1 set down on June 2, 1966, just 14 km (9 mi) off target in the Ocean of Storms. Over 11,000 high-resolution, close-up photographs of the moon were taken and transmitted back to earth. • Surveyor 3 touched down in the Ocean of Storms on April 20 following liftoff three days earlier aboard an Atlas Centaur. Surveyor 3 sent back its lunar-surface photographs and invaluable data obtained by a digging and scraping mechanism that was used to determine the mechanical properties of the lunar soil. The sampler confirmed that the moon could bear the weight of an Apollo manned spacecraft. Initial analysis showed that the soil resembled a hard-packed wet sand and that its strength increased with depth. The spacecraft did not, however, survive the two-week lunar night, when temperatures dropped to approximately –160° C (–260° F). • Surveyor 5, launched on September 8, began sending close-up photographs of the lunar surface on the 11th. It also carried an experimental package that made chemical tests by the use of alpha-ray bombardment. Preliminary analyses revealed that the lunar-surface material is much like terrestrial rock. It indicated the existence of basalt, which is a dark, dense, fine-grained igneous rock. Silicon was especially noted as a constituent of the soil beneath the spacecraft. Surveyor 5 survived a lunar night and proceeded to commence operations again on October 15. • Surveyor 6, launched on November 7, had to land in rough terrain in Sinus Medii, a plain just south of the equator. The lander made measurements with an onboard soil analyzer. On November 17 it was commanded to make a "hop" on the moon's surface. Its 6.5-second flight took it about 3 meters (10 ft) high to a landing 2.4 meters (8 ft) away. The maneuver provided new data on the lunar-surface bearing strength. • The site selected for Surveyor 7 was the highland area around the crater Tycho, at nearly 41° south latitude. Launched on Jan. 7, 1968, Surveyor 7 landed on the evening of January 9. Devices were aboard the probe to dig into the lunar surface and analyze the scooped-out materials. With the successful conclusion of Surveyor 7's work, the U.S. unmanned lunar-exploration program came to at least a temporary end.
Other Unmanned Missions • Round-Trips to the Moon. On Sept. 15, 1968, the Soviet Union launched Zond 5 on a trajectory that sent the probe arching behind the moon and back to earth, where it parachuted to a landing in the Indian Ocean on September 21. It was recovered the following day. The probe, which was a test for manned lunar craft, became the first spacecraft to make the round trip. • Sample-Return Missions. The Soviet Union's Luna 16, launched on Sept. 12, 1970, became the first unmanned spacecraft to land on the moon and then return safely to earth. The probe set down in the Sea of Fertility just south of the moon's equator on September 20. Luna 16 transmitted pictures of its landing site, and its robot electric drill dug 35 centimeters (14 in) into the surface, retrieving rock samples. A capsule that had formed part of the original spacecraft returned these samples to earth on September 24. • Later Lunar Missions. After the Apollo and Luna programs were completed in the 1970s, there was a 14-year hiatus in lunar missions until Japan paid its first visit to the moon, in 1990. The MUSES-A satellite was launched into a highly elliptical earth orbit on January 24. Renamed Hiten (after a Buddhist angel) once in orbit, it flew by the moon on March 19, where it released the tiny 12-kg (26-lb) Hagoromo probe into lunar orbit. Hagoromo's radio transmitter failed almost immediately. Hiten continued to make regular flybys of the moon and was placed in lunar orbit in February 1992. It was intentionally crashed into the moon in April 1993. • The United States launched its first lunar mission in over 20 years on Jan. 25, 1994. After two flybys of the earth, Clementine, a joint NASA/Department of Defense probe, entered lunar orbit on February 19, where it spent nearly two months mapping the moon at a variety of frequencies. In a radar experiment Clementine discovered what could be ice water at the bottom of a permanently shadowed crater near the moon's south pole, though other results raised questions about this conclusion. On May 5 Clementine left lunar orbit in an effort to rendezvous with the asteroid Geographos, but a propulsion failure two days later doomed that part of the mission. • The Lunar Prospector probe, launched by NASA on Jan. 6, 1998, and entering lunar orbit five days later, returned data that seemed to indicate large amounts of ice water in the moon's polar regions. The probe was also intended to estimate the abundance of a number of elements on the lunar surface.
Reaching for the Moon • Plans for a crewed lunar expedition began in the late 1950s. • In 1957 the Soviet Union launched the first satellite, Sputnik I. • In 1961, Soviet cosmonaut Yuri A. Gagarin became the first human in space. • On May 5, 1961, Alan B. Shepard Jr. became the first American in space as part of Project Mercury followed by the two-person crews of Project Gemini. • On July 20, 1969, the Apollo program landed Neil Armstrong and Buzz Aldrin on the Moon, during Apollo 11.
Mercury (1961-1963) First American Spacecraft to carry astronauts Mercury 3: 1st Mercury flight (Shepard) Mercury 6: 1st to orbit Earth (Glenn) Mercury 9: Final flight in series
Gemini (1965-1966) Designed for 2 astronauts Purpose was: • to find out if a human could survive and work in weightlessness of space • to train astronauts to maneuver the spacecraft
Apollo (1968-1972) • Accomplished Pres. Kennedy’s goal. • Apollo 8 & 10 (1969)orbited the moon • Apollo 11(1969) landed on moon. Neil Armstrong and Edwin Aldrin were first people to walk on moon. • Apollo 12, 14, 15, 16, 17 all landed on the moon. All returned safely to earth. • Collected samples(380 kg of rock and soil samples) • Set up instruments to measure moonquakes, magnetic field, solar wind particles, gases.
Space Shuttle • Designed to be reused • 3 main units: • orbiter (airplane body)with 3 main engines, • external tank which feeds propellants to engines in first stage, • two solid rocket boosters that provide the energy for the initial lift-off. • Remote Manipulator System (RMS)-robotic arm • Used to launch and maintain scientific and technological instruments
Moon’s Unique Features • Earth’s moon is one of the largest moons in the solar system, especially compared to the size of the planet it orbits. • The Moon is relatively farther from Earth than most moons are from the planets they orbit. • Earth’s moon is a solid, rocky body, in contrast to the icy composition of the moons of the outer planets. • Earth’s moon is the only large moon among the inner planets.
Properties of Moon • ¼ size of Earth • Less density and mass than earth • Low gravity and escape velocity means that it is easier to launch spacecraft from the moon than earth • Layered structure • Slightly egg-shaped
The Lunar Surface • The albedo of the Moon, the amount of sunlight that its surface reflects, is only about 0.07 (7 percent) contrasted with Earth’s average of 0.31 (31 percent). • Because the Moon has no atmosphere, surface temperatures can range from 400 K (127°C) in sunlight to 100 K (–173°C) where it is dark. • There is no erosion on the Moon—except for surface creep and wear caused by recent impacts—because it has no atmosphere or flowing water. • Craters on the Moon are preserved until one impact covers another.
The Lunar SurfaceThe surface of the Moon consists of several features: The Highlands are lunar regions that are light in color, mountainous, and heavily covered with craters. The Maria (singular, mare) are lunar regions that are dark, smooth plains, which on average are 3 km lower in elevation than the highlands.
Lunar Highlands • Mountain ranges at end of maria • Light colored, coarsely crystalline igneous rock • Breccias-rocks made of angular fragments cemented together. Mostly gray. • Probably formed by meteoroid impacts that melted rocks together.
Lunar Maria • mare - a large, dark area of basalt on the moon • Galileo thought they were seas! • Smooth plains with huge circular basins • Examples: Mare Imbrium, Mare Crisium, Mare Sereniatis, Oceanus Procelarum • Rocks resemble basalt in lava flows in Hawaii and Iceland
The Lunar SurfaceThe surface of the Moon consists of several features: • Impact craters were formed when objects from space crashed into the lunar surface. • Ejecta is material blasted out during impacts that fell back to the surface. • Rays are long trails of ejecta that radiate outward from some craters. • Rilles are meandering, valleylike structures that are found in the Maria.
Lunar Craters and Rays • crater - a bowl-shaped depression that forms on the surface of an object when a falling body strikes the object’s surface or when an explosion occurs • Most of the craters formed when debris and meteoroids struck the moon about 4 billion years ago. • Largest, “Clavius” 240 km across • Circular with rugged cliff rims • Rays-bright streaks that radiate from crater. Consist of shattered rock and dust splashed out by meteoroid’s impact
Composition • The Moon is made up of minerals similar to those of Earth—mostly silicates. • The highlands are predominately lunar breccias, which are rocks formed by the fusing together of smaller pieces of rock during impacts. • The maria are predominately basalts that contain no water.
Lunar Rocks Lunar rocks are igneous, and most rocks near the surface are composed mainly of oxygen and silicon. Differ from earth rocks: • Contain no water • Greater proportions of elements with high melting points such as aluminum, titanium, zirconium • Less amounts of elements with low melting points such as sulfur and lead
Lunar Soil • The moon’s surface is very susceptible to meteorite hits because the moon has no atmosphere for protection. • Over billions of years, these meteorites crushed much of the rock on the moon’s surface into a layer of dust and small fragments called regolith. • The depth of regolith on the moon varies from 1 m to 6 m and is composed of loose rock material of all sizes • No water • No organics
The Interior of the Moon • The interior of the moon is less dense than the interior of earth. • Scientists have determined that the moon’s interior is layered by studying seismic information collected during moonquakes. • Like, Earth, the moon has three compositional layers: the crust, the mantle, and the core.
The Moon’s Crust • The side of the moon that faces Earth is called the near side, while the side of the moon that faces away from Earth is called the far side. • The moon’s crust is thicker on side than the other. • The crust on the near side is about 60 km thick. The crust on the far side is up to 100 km thick. • The difference in thickness was caused by the pull of Earth’s gravity during the formation of the moon.
Motions of the Moon The length of time it takes for the Moon to go through a complete cycle of phases is called a lunar month. The length of a lunar month is about 29.5 days, which is longer than the 27.3 days it takes for one revolution, or orbit, around Earth. The Moon also rises and sets 50 minutes later each day because the Moon has moved 13° in its orbit over a 24-hour period, and Earth has to turn an additional 13° for the Moon to rise. See visual
Lunar Month One new moon to the next. 29.5 days Earth has moved 27.3 degrees, moon must revolve 2 more days
Synchronous Rotation Synchronous rotation is the state at which orbital and rotational periods are equal. As the Moon orbits Earth, the same side faces Earth at all times because the Moon has a synchronous rotation, spinning exactly once each time it goes around Earth.
Phases of the Moon The sequential changes in the appearance of the Moon are called lunar phases. A new moon occurs when the Moon is between Earth and the Sun and we cannot see the Moon because the sunlit side is facing away from us. As the Moon moves along in its orbit, the amount of reflected sunlight that we can see increases until we are able to see the entire sunlit side of the Moon, known as a full moon. Once a full moon is reached, the portion of the sunlit side that we see begins to decrease as the Moon moves back toward the new-moon position. See visual
Moon’s Orbit • elliptical orbit – 27 1/3 days – 13 degrees/day • Earth moves around sun – 1 degree/day • not exactly on same plane (5 degrees) Fig.24.12 • sun diameter 400X moon but 400X farther away…look same size • rises in east, sets in west (apparent)
The Effects of Orbits The Moon’s orbit is tilted 5° relative to the ecliptic and usually the Moon passes north or south of the Sun as seen from Earth, during a new moon. A solar eclipse can occur only when the intersection of the Moon and the ecliptic is in a line with the Sun and Earth.
Phases of the Moon • During which phase(s) of the moon does the visible portion of the moon appear as a semicircle? • During which phase of the moon is it possible to see a solar eclipse from Earth if the moon happens to be crossing the plane of Earth’s orbit at that time? • How much time elapses between a full moon and a new moon? • Is a different part of the moon’s surface visible at each full moon? Explain your answer. • The unlit portion of a crescent moon is slightly visible from Earth. What is the source of this light?
Differentiation of the Lunar Interior • Early in its history, the lunar surface was covered by an ocean of molten rock. • Over time, the densest materials moved toward the center of the moon and formed a small core. • The least dense materials formed an outer crust. • The other materials settled between the core and the outer layer to form the moon’s mantle.
Meteorite Bombardment • When the moon first formed, it was bombarded with meteorites, creating craters and regolith on the moon’s surface. • About 3 billion years ago, less material struck the lunar surface, and few new craters formed. • Craters that have rays formed during the most recent meteor impacts. During this stage, virtually all geologic activity stopped on the moon.
Lava Flows on the Moon • After impacts on the moon’s surface foremd deep basins, lava flowed out of cracks, or fissures, in the lunar crust. • This lava flooded the crater basins to form maria. • The presence of maria suggest that fissure eruptions once characaterized the moon. • Because of the uneven thickness of the moon’s crust, more maria formed on the near side of the moon than on the far side.
Tectonics on the Moon? • The Moon, like Earth, has a layered structure, which consists of the crust, the upper mantle, the lower mantle, and the core. • Although the Moon experiences moderate moonquakes approximately once a year, scientists theorize that the Moon is not tectonically active. • That the Moon has no active volcanoes and no significant magnetic field supports this conclusion.
History of the Moon • Radiometric dating of lunar rocks from the highlands indicates an age between 3.8 and 4.6 billion years. • Regolith- is a layer of loose, ground-up rock on the surface of the Moon that formed as a result of the heavy bombardment during its first 800 million years. • The maria which are between 3.1 and 3.8 billion years old formed when lava welled up from the Moon’s interior and filled in the large impact basins.
The Formation of the Moon The Giant Impact Hypothesis • Most scientists agree that the moon formed in three stages. • The giant impact hypothesis states that the formation of the moon began when a large object collided with Earth more than 4 billion years ago. • The collision ejected chunks of Earth’s mantle into orbit around Earth. The debris eventually clumped together to form the moon. • This hypothesis explains when moon rocks share many of the chemical characteristics of Earth’s mantle.
Formation Theories • The impact theory is the most commonly accepted theory of how the Moon formed. • This theory proposes that the Moon formed as the result of a gigantic collision between Earth and a Mars-sized object about 4.5 billion years ago, when the solar system was forming. • See visuals
Formation Theories • The capture theory proposes that as the solar system was forming, a large object ventured too near to the forming Earth, became trapped in its gravitational pull, and formed into what is now the Moon. • The simultaneous formation theory states that the Moon and Earth formed at the same time and in the same general area, and thus the materials from which they formed were essentially the same.