The Moon had a relatively high-density atmosphere about 3–4 billion years ago. Gases emitted during volcanic eruptions had formed this ancient atmosphere, which was later destroyed by solar winds — all these gases dissipated into space.
The Moon has no atmosphere or weather, and the sky always appears black, even during the day. The Sun's light travels in a straight path without scattering, keeping all colors together.
The other side of the Moon had been hidden unless a spacecraft able to take a turn around the satellite and take pictures was invented. In 1959, Soviet station Luna 3 was the first to do this.
There are hundreds of moon trees growing on Earth now. In 1971, as part of the experiment, the Apollo 14 crew took 500 tree seeds with them to the Moon and returned them back to the Earth. Nearly all the seeds successfully germinated.
There is plenty of water on the Moon. Ice deposits with a total mass of over 600 million tons were found in the north pole alone. This ice is located mainly on the craters’ bottom.
There are earthquakes on the Moon, or more correctly moonquakes. Moonquakes are much weaker than earthquakes. They occur less often but last much longer.
The Moon's atmosphere is extremely rare — it's 10 trillion times less dense than the Earth's one. Even if gases are released from under the Moon's crust, they simply dissipated into space. The Moon's gravity is not able to hold them.
We can see the ocean tides on Earth thanks to the Moon. The Moon's gravity makes two bulges in the Earth's oceans — on the side facing toward the Moon and on the opposite one.
The distance between the Earth and the Moon is not constant. It can vary by about 43 thousand kilometers. The average distance between them is 384 thousand kilometers.
The Moon's mean distance from the Earth is constantly increasing. Fortunately, the change rate is very slow—about four centimeters per year.
To calculate the mass of an object on the Moon, you only need to divide it by 6. For example, a person with a weight of 75 kg on Earth would weigh about 12.5 kg on the satellite. It's all about the free-fall acceleration which is only 16.5% of that on the Earth.
The temperature all over the Moon's surface varies greatly. It ranges from -171°C at night to +140°C during the day. And it drops down to -238°C in the craters.
The mass of the Moon is about 81 times less than that of the Earth, but the volume is only 50 times less.
Lunar dust (which meant a "rock blanket" in ancient Greek) is commonly known as "regolith." Unsurprisingly, a thick layer of dust covers almost the entire satellite's surface.
Lunar dust is a serious problem for astronauts and also moon rovers. The dust layer ranges in thickness from 15 centimeters to tens of meters, while the dust itself is very fine and sharp, like tiny pieces of glass. It easily clings to surfaces.
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