ELI5: Explain Like I'm 5

Mare Tranquillitatis

Mare Tranquillitatis is a place on the moon where there was a very important event that happened a long time ago. It's basically a big area on the surface of the moon that looks like a big, flat circle.

In 1969, a really brave group of people called astronauts traveled all the way to the moon in a spaceship called Apollo 11. They landed in Mare Tranquillitatis and set up a little house that they called a "landing module."

One of the astronauts, named Neil Armstrong, was the very first human to step onto the surface of the moon. He said some really famous words that lots of people still remember today: "That's one small step for man, one giant leap for mankind."

The Mare Tranquillitatis is a really special place because it's where people first learned that it's possible for humans to travel all the way to the moon and walk around on it!