WHAT THE MOON IS LIKE:
       When we look at the moon, it looks like a smooth sphere with dark and light patches of gray. In the 1600's, Galileo was able to see other features as well. With field glasses or a simple telescope one can see that the dark patches are flat plains, called maria. Mare are lowland rocks that are covered with a thin layer of rocky soil. The light spots are parts on the moon where it is mountainous, called the highlands. Most of the maria were formed about 3.3 to 3.8 billion years ago by lava flows.
       Craters are the most abundant properties on the moon. The moon has craters inside of craters and some that even connect to one another. The small craters are bowl-shaped. Large craters are rimmed by mountains and have steep, terraced walls. The largest crater is the Imbrium Basin, which is 700 miles wide. It's floor is covered by dark lava, forming one "eye" of the moon.
       Some craters are called ray craters because they are surrounded by light gray strips. These rays look like bright splashes of material that extend in many directions. Secondary craters are formed in the rays by rocks thrown out of the ray craters. These rays are composed of broken rock.
       The formation of small craters was caused by the impact of meteoroids. Larger craters were formed by comets or asteroids which hit the moon. These are much larger than meteoroids. It is believed that the moon's largest craters must have been formed by planetesimals, solid objects that may have even formed the moon.
       Some of the craters on the moon resemble the volcanic craters on our earth. These craters are often found on tops of small mountains or hills. Some of the mountains are as tall as the ones we see on earth. In addition to mountains, the moon has narrow valleys, called rilles. Rilles are straight and were probably the result of the outer crust cracking. Sinuous rilles are winding valleys that look almost like riverbeds. It seems that these were formed from lava flow.

COMPOSITION
       The moon's composition has been of great interest to scientists. With the collection of moon soil and moon rocks by astronauts, many questions have been able to be answered. Moon soil contains no fossils of plants or animals, but when this soil is placed on earth plants, they seem to grow better.
       Moon rocks are composed of minerals including aluminum, calcium, magnesium, oxygen, silicon, and titanium. Some gases are also trapped in these rocks, such as hydrogen and helium. These gases are said to have reached the moon by solar wind.
       Astronauts collect two main types of rock, basalt and breccia. Basalt is formed from hardened lava and is made of feldspar, proxene and ilmenite crystals. These minerals were formed at 2200 degrees, which proves that the moon was extremely hot when it was forming. Breccia is made of soil and rock that have been squeezed together when hit by falling objects.
       The moon's outer crust seems to be solid and hardy but not much is known about its inner material. When Apollo 13 sent part of the Saturn rocket crashing on to the moon, the result was seismic vibrations which lasted for four hours. These vibrations were not expected by the scientists.

CONDITIONS:
       Astronauts can walk easily on the moon, regardless of all of their heavy tools and supplies. The force of gravity on the moon is six times less than on the earth. Gravity is weaker there because the mass is 81 times smaller than the earth's mass.
       The moon has little to almost no atmosphere. If the moon had a layer of gases, it would have leaked away because of the low gravity. Becuase it has no atmosphere, the moon has n o type of weather and no clouds, rain, or wind. The moon has no water on it's surface. There is no air to carry sound or for astronauts to breathe.
       The surface of the moon can become hotter or colder than any place on earth. At the equator of the moon, the temperature can reach up to 260 degrees and drop as low as -280 degrees. In some craters the temperature is always around -400 degrees Fahrenheit. 

This is a picture of on the Apollo 17 mission, astronaut Harrison Schmitt
is standing next to a boulder at Taurus-Lithow during the 3rd EVA.

MOVEMENT OF THE MOON:
       Following an elliptical orbit, the moon travels around the earth at 2,300 miles per hours. One trip or revolution is 1,4 million miles. The moon also travels with the earth as it circles the sun. The moon moves west to east on our sky, but seems to move east to west because the earth spins much faster than the move can revolve around the earth.
       Since the orbit is oval shaped, the moon is not always the same distance away from the earth. The point where it comes the closes to the earth is called perigee. This is 221,456 miles away. The farthest point, apogee, is 252,711 miles.
       The gravitational pull keeps the earth's moon in its orbit. The moon's revolution around earth is measured in synodic months and sidereal months. A synodic month is about 29 1/2 days long, and is the period from one new moon to the next new moon. This is the amount of time it takes to revolve around the earth relative to the sun. A synodic month is one full day on the moon. The lunar day is classified in to two weeks of light and two weeks of darkness. A sidereal month is about 27 1/3 days, and is the amount of time it takes for the moon to travel around the earth in relation to stars.

ROTATION:
       The moon rotates on its axis only once during its trip around the earth. The moon rotates from the west to the east, the same direction that it travels around the earth. At its equator it rotates about 10 miles per hour.
       Sometimes a short distance around the edge of the moon can be seen, called the limb. It seems to swing up and down and from side to side during each revolution. These type of motions are called liberations. They are caused by changes in the moon's speed of revolution and by a tilt of 5 degrees. Liberations allow us to see about 59 percent of the moon.
      

PHASES:
       The moon has many phases. During a synodic month we see the moon change from a crescent to a full circle and back. These seemingly changes in shape and size are due to different lighting conditions. Different amounts of sunlight is reflected by the sun to the earth, causing these phases. The shape appears to change because we see different parts of the moon's surface as it makes its orbit.
       When the moon is in between the sun and earth, its far side is turned away from the earth. It seems to be a darkened phase and is called a new moon. In the new moon phase, the side of the moon is lighted by earthshine, sunlight that is reflected from the earth to the moon.
       A day after the new moon, a thins slice of light can be seen, The line between the sunlit part and the dark part is called the terminator. Each day, more and more of the moon's sunlit side is seen. After seven days, we see half of a full moon. This half circle is exposed to the sun and can be seen from the earth. It is called the first quarter. Seven days after the first quarter, the moon moves to where the earth is between it and the sun. This phase is the full moon. Seven days after the full moon, we see a half of a full moon once again. This is known as the last or third quarter. After one more week, the moon returns to the new moon phase.
       As the moon changes from a new moon to a full, it is called waxing. During the period from full to new, the moon is waning. When it seems to be smaller than half of a moon, it is called a crescent. When it seems to be larger than half of a moon, it is called a gibbous.
       The moon rises and sets at varying times. The moon rises above the horizon. With each passing day, the moon rises about 50 minutes later and drops about 12 degrees. By the end of a week, the moon rises at noon and sets at midnight. During the full moon, it rises as the sun sets and sets as the sun rises. During the last quarter, it rises at midnight and sets at noon.

ECLIPSES:
When a full moon passes through the earth's shadow, we see an eclipse of the moon. During a lunar eclipse, the moon is a dark reddish color. It is lighted by faint red rays from the sun that have been refracted by the atmosphere of earth.
       During another eclipse, the moon passes directly between the earth and the sun. When part of the sun is hidden by the moon. we see a solar eclipse. (For more information on solar eclipses, visit the SUN)

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