Luna is a beautiful world that lies some 384,400 kilometers (almost 239,000 miles) from Earth. It is littered with mountains, valleys, old volcano sites, and many bowl-like holes called craters. Luna is a neat world to explore because you can see it without a telescope or binoculars. I know you have seen it. In fact, you may even see it tonight, that is because Luna is our moon.
For thousands of years, this fascinating place has been written about in stories and poems, sung about in songs, and been included in folklore and legends. But, did you know that our moon has some very important functions? The moon regulates the ocean tides on Earth. It also keeps the Earth's tilt on its axis regular. This is why we have seasons here on Earth. When the North Pole is tilted towards the sun, then the Northern Hemisphere is in its warmer seasons, like summer, and the Southern Hemisphere is in its colder seasons. When the South Pole is tilted towards the sun, then the Southern Hemisphere has its warmer seasons and the Northern Hemisphere is colder. The tilting of the Earth on its axis is also known as Earth's wobble on its axis.
As you observe the moon from your back yard, you will probably notice right away that some areas are darker than others. This is because long ago there were many comets and asteroids, many more than today, which frequently hit the worlds of our Solar System. Every once in a while, a very large object would crash into the Moon hard enough to break through its surface rock causing lava to ooze out. When you see a dark area, you are looking at an ancient bed of lava rock from one of these impacts. If a large object struck the Moon today, it would not cause a volcano, however. This is because the core of the Moon has almost completely cooled down, meaning there is no longer any lava in the core to ooze from its rock surface. The lighter areas on the surface of the moon are where objects have crashed into the surface more recently. But recently in astronomy terms can mean a million years ago. In photographs of the Moon, you can see large scars called craters. Craters are caused by collisions between the Moon and other objects, such as asteroids or comets.
The moon has been explored many times in the last half century. You probably know that astronauts landed on the Moon in 1969. But did you know that this was not the first successful contact humans made with the moon? And did you know that astronauts landed on the moon more than once? It's true!
In 1959, the Soviet Union launched a probe, called Luna 1, into space that was supposed to crash into the surface of the Moon to study the soil and radiation in space. This probe unfortunately malfunctioned and it missed hitting the Moon. Instead, it flew past the Moon and into space. Contact with this probe was lost as it flew away into space. Later that same year, the Soviet Union was successful in landing a probe on the Moon, Luna 2. This probe had sensors on board that allowed scientists back on Earth to study interplanetary space and sodium gas. Luna 2 made history because it was the first man-made object to make contact with another object in space.
Following this, more probes and satellites were sent to the Moon by the U.S. and Soviet Union. Some impacted the surface like Luna 2, some landed softly on the Moon, and others simply orbited the Moon and mapped out possible landing sites for future missions.
Then, on July 20, 1969, American astronauts landed on the surface of the Moon in a spacecraft named the Apollo 11. Neil Armstrong was the first human being to step onto the surface of the Moon. This mission was followed by 5 more successful missions to land on the Moon. In total, 12 astronauts walked on the surface of the Moon from 1969 to 1972. The astronauts collected 382 kg (842 pounds) of rock samples from the moon during these missions. They conducted many scientific experiments also, including solar wind experiments, soil, magnetic field experiments, and many others. They were also able to travel around on the surface of the Moon in a rover vehicle that kind of looked like a dune buggy.
Many scientists consider the Earth and Luna, or Moon, to be a double planet system. This is because they are so close in size.