Britannica LaunchPacks | Space Exploration Space Exploration For Years 3-5 This Pack contains: 4 ARTICLES 1 IMAGE 2 VIDEOS © 2020 Encyclopædia Britannica, Inc. 1 of 18 Britannica LaunchPacks | Space Exploration Moon Although the Moon may seem small and insignificant compared to the rest of the universe, its size and location make it very important to Earth. Other than the Sun it is the most visible body in the sky. Because of this, humans have been fascinated by the Moon since ancient times. It has been studied both from Earth and from space. In fact, more than 70 spacecraft have been sent on missions to the Moon. In addition, the Moon is the only place outside Earth that has been visited by humans. A view of the near side of the Moon shows some of its many craters. Photo NASA/JPL/Caltech (NASA photo # PIA00405) The Moon is the most prominent feature in the night sky. © Dmytro Pylypenko/Dreamstime.com The average distance of the Moon from Earth is about 384,400 kilometres (238,900 miles). This may seem like a great distance. However, compared to the distance of Earth from other planets, the Moon is actually quite close. © 2020 Encyclopædia Britannica, Inc. 2 of 18 Britannica LaunchPacks | Space Exploration Physical Features The Sun is the closest star to Earth, but it is still very far away. The distance from Earth to the… Encyclopædia Britannica, Inc./Patrick O'Neill Riley The Moon is slightly more than a quarter of the size of Earth. It is made of solid rock. The surface is covered with a layer of dust consisting of fine-grained rock fragments. The Moon’s landscape features include craters, mountain peaks, deep narrow valleys and plains, which are sometimes called maria. Highlands When looking at the Moon from Earth, some areas appear light-coloured and other areas appear dark-coloured. The light areas of the Moon are the highlands. These highlands are covered with thousands of craters, some of them overlapping one another. Astronomers are not sure about their origin, though many believe that they are the result of meteorites hitting the Moon’s surface. The highlands also contain mountain ranges. These mountains were given such names as the Alps, Pyrenees and Carpathians, after mountain ranges on Earth. Plains The dark areas on the Moon are large plains, or maria. The word maria comes from the Latin word mare, which means ‘sea’. It is believed that these plains are craters that were filled with lava billions of years ago. The plains on the Moon have names such as Mare Imbrium (‘Sea of Showers’) and Mare Nectaris (‘Sea of Nectar’). Mare Imbrium is the largest plain. It is about 1,120 kilometres (700 miles) in diameter. Temperature The Moon’s temperature varies greatly depending on whether it is facing the Sun. When the surface faces the Sun during the Moon’s day, the average temperature is about 107°C (225°F). At night on the Moon, when the Sun’s rays do not reach the Moon’s surface, the temperature cools to about -153°C (-243°F). Orbit and Spin Like the planets, the Moon has two types of movement, known as orbit and spin. The orbit is the path that the Moon travels around Earth. It takes the Moon about 27 days to make one orbit of Earth. The Moon also spins on its axis. The axis is an imaginary line that passes through its poles. It takes the Moon about the same amount of time to make one complete revolution on its axis as it takes it to orbit Earth. For this reason, the same side of the Moon always faces Earth. © 2020 Encyclopædia Britannica, Inc. 3 of 18 Britannica LaunchPacks | Space Exploration Phases of the Moon The same side of the Moon always faces Earth. This side is called the Moon's nearside. As the Moon… Encyclopædia Britannica, Inc.; source: U.S. Naval Observatory The diagram shows the position of the Moon at each of its phases. The enlarged pictures of each… Encyclopædia Britannica, Inc. Photos Yerkes Observatory, University of Chicago When viewed from Earth, the Moon appears to go through different phases. Sometimes it looks like a full circle while other times it appears as only a thin crescent. This is because the Moon reflects the light from the Sun. As the Moon travels around Earth in its orbit different parts of the Moon are exposed to the Sun’s light. When the Moon is on the other side of Earth from the Sun, the Sun is shining directly on the Moon, and the Moon looks full. However, when the Moon is between the Sun and Earth, the Moon looks dark since the Sun is behind the Moon. In each cycle of the Moon’s orbit around Earth, the Moon displays four main phases: new (when the side of the Moon that faces Earth is dark), first quarter, full and last quarter. It takes the Moon about 29 days to complete this cycle. Eclipses Sometimes the position of the Moon in relation to the Sun and Earth results in an eclipse. In astronomy, an eclipse occurs when one body is either completely or partially hidden from view by another body. © 2020 Encyclopædia Britannica, Inc. 4 of 18 Britannica LaunchPacks | Space Exploration During a lunar eclipse the moon, revolving in its orbit around Earth, passes through the shadow of… Encyclopædia Britannica, Inc. When Earth comes between the Moon and the Sun, it prevents the Sun’s rays from reaching the Moon. The Moon is then in the shadow of Earth and is hidden from view. This is known as a lunar eclipse. During an eclipse of the sun, the shadow of the moon sweeps over the surface of Earth. In the darkly … Encyclopædia Britannica, Inc. Another kind of eclipse occurs when the Sun is temporarily hidden from view on Earth. This happens when the Moon comes between the Sun and Earth. This is a solar eclipse. How the Moon was Formed Many astronomers think that a large body, perhaps the size of the planet Mars, struck Earth early in the history of the solar system. As a result, a cloud of fragments was thrown out around Earth. These fragments later combined to form the Moon. Observation and Exploration Because the Moon is the brightest object in Earth’s night sky, it has been observed by people since ancient times. In the 1600s the invention of the telescope allowed the Italian scientist Galileo and others to study the Moon more closely. In the same century Isaac Newton discovered a force called gravity. He also figured out that the pull of gravity from the Moon affects the level of the seas, causing tides to occur. For the following 300 years scientists continued to study the Moon from Earth. In 1957, the space age began when the Soviet Union launched an artificial satellite called Sputnik. This gave scientists greater freedom to study bodies in outer space. Throughout the early 1960s, the United States and the Soviet Union launched many spacecraft that flew by, crashed into or orbited the Moon. These missions provided close-up photographs of the Moon. In 1966 the Soviet craft Luna 9 became the first spacecraft to land on the Moon. This important mission provided photographs of the lunar soil. From 1966 to 1968, the United States and the Soviet Union continued sending unmanned craft to orbit or land on the Moon. These missions paved the way for the historic landing of Apollo 11 on the Moon. © 2020 Encyclopædia Britannica, Inc. 5 of 18 Britannica LaunchPacks | Space Exploration On 20 July 1969, US astronauts Neil Armstrong and Edwin ‘Buzz’ Aldrin, Jr, of the Apollo 11 mission, were the first men to walk on the Moon. There they set up experiments and took photographs. Armstrong and Aldrin returned to Earth with about 22 kilograms (48 pounds) of rock and soil samples that they had collected. From 1969 to 1972, the United States landed five more crews on the Moon. The Soviet Union placed vehicles operated by robots on the lunar surface until 1976. From 1977 until 1990, no missions to the Moon occurred as the United States and the Soviet Union studied other parts of the solar system. In 1990, the Japanese Space Agency launched a satellite that was put into orbit around the Moon. The next major US mission was the Lunar Prospector, which was launched in 1998. It was a small, unmanned spacecraft that orbited the Moon and mapped its surface. After a year, the craft was deliberately crashed into the Moon to look for evidence of water. It did not find any water. Citation (MLA style): "Moon." Britannica LaunchPacks: Space Exploration, Encyclopædia Britannica, 19 Feb. 2021. packs-ngl.eb.com. au. Accessed 5 Aug. 2021. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. rocket Flying devices called rockets come in many sizes, from simple fireworks to the engines that are used to launch missiles, satellites and spacecraft. The vehicles driven by rockets are often called rockets themselves. Rocket fuel can be liquid or solid. When the fuel burns, it gives off gas that pushes the rocket… Encyclopædia Britannica, Inc. © 2020 Encyclopædia Britannica, Inc. 6 of 18 Britannica LaunchPacks | Space Exploration How Rockets Work Like jet aeroplanes, rockets are jet-propelled. All jet-propelled vehicles rely on a chemical reaction called combustion to provide the force to move them through the air. A fuel onboard the craft is mixed with oxygen.