Mare Tranquillitatis

Mare Tranquillitatis, or the Sea of Tranquility, is a vast, flat area on the Moon, formed by ancient volcanic activity. It is one of the lunar maria—dark, basaltic plains that are less cratered than surrounding areas. The Sea of Tranquility gained historical significance as the landing site of Apollo 11 in 1969, where astronauts Neil Armstrong and Buzz Aldrin became the first humans to set foot on the Moon. The name reflects the calm appearance of the region, which is visible to the naked eye from Earth, often being one of the first landmarks people notice on the lunar surface.