| Moon | |
|---|---|
| |
| Full Moon in 2010. | |
| Diameter | 3,476 km 2,160 mi. |
| Distance from the Earth | 384,400 km 238,900 mi. |
| Mass | 7.3477×10^22 kg (0.012300 Earths) |
| Density | 3.3464 g/cm^3 |
| Symbol | 
|
The Moon (Luna) is the only natural satellite of the Earth, and the fifth largest satellite in the Solar System. About one-sixth of the Earth's gravity.[1]
While there are only two basic types of regions on the Moon's surface, there are many interesting surface features such as craters, mountain ranges, rilles, and lava plains. The structure of the Moon's interior is more difficult to study. The Moon's top layer is a rocky solid, perhaps 800 km thick. Beneath this layer is a partially molten zone. Although it is not known for certain, many lunar geologists believe the Moon may have a small iron core, even though the Moon has no magnetic field. By studying the Moon's surface and interior, geologists can learn about the Moon's geological history and its formation.[1][2]
Orbit[]
DSCOVR satellite sees the Moon passing in front of Earth
A double planet were taken by the Galileo spacecraft.
The Moon completes its orbit around the Earth in approximately 27.32 days. The Earth and Moon orbit about their barycenter, which lies about 4600 km from Earth's center.
Conditions[]
Astronaut Harrison Schmitt standing next to boulder during third EVA.
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. Because it has no atmosphere, the Moon has no 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° and drop as low as -280°. In some craters the temperature is always around -400°F.
Lunar Phases[]
The libration of the Moon over a single lunar month. Also visible is the slight variation in the Moon's visual size from Earth.
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°. Liberations allow us to see about 59% of the Moon.
Eclipses[]
The Moon, tinted reddish, during a lunar eclipse. October 8, 2014.
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.
The Moon blocking the Sun during the total total eclipse of August 21, 2017.
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.