Mare Tranquillitatis

Moon · space exploration · lunar geography

First human landing. On July 20, 1969, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin landed at Tranquility Base, making Mare Tranquillitatis the first spot on another world where people ever walked.

Dark lunar sea. Mare Tranquillitatis is a 'mare,' which means 'sea' in Latin, though it contains no water. These dark, flat regions on the Moon are actually ancient lava flows that cooled billions of years ago.

Smooth landing zone. Astronauts chose this area because its flat, smooth surface made it safer for landing than the Moon's cratered highlands.

Ancient basin floor. Mare Tranquillitatis sits inside the Tranquillitatis basin, a giant impact crater that formed when an asteroid hit the Moon long ago.