Apollo 11 · Tranquility Base

Apollo 11 was the NASA mission that first landed people on the Moon. On 20 July 1969 the lunar module Eagle touched down on a flat, dark plain called the Sea of Tranquility. The crew named the spot Tranquility Base. Neil Armstrong stepped out first, Buzz Aldrin followed, and Michael Collins circled overhead in the command module Columbia.

The landing answered a challenge President Kennedy set in 1961: to land astronauts on the Moon and bring them safely home. Armstrong and Aldrin stayed on the surface for about 21 and a half hours, walked outside for about two and a half hours, and brought back about 21.5 kg of Moon rock and soil. All three astronauts splashed down in the Pacific Ocean on 24 July 1969.

The mission

A Saturn V rocket launched the crew from Florida on 16 July 1969. Four days later Armstrong and Aldrin flew Eagle down to the surface while Collins waited in orbit. Armstrong radioed that the Eagle had landed, and hours later he climbed down the ladder and spoke his famous words about one small step for a man and a giant leap for mankind. The two astronauts collected samples, took photographs and set up experiments before lifting off to rejoin Collins.

What was left behind

The bottom half of Eagle, called the descent stage, still stands at Tranquility Base, with a plaque on its ladder that ends with the words: we came in peace for all mankind. The crew also left a seismometer to listen for moonquakes and a laser reflector, a panel of special mirrors. Scientists on Earth still bounce laser beams off it to measure the distance to the Moon very precisely. The American flag was blown over by the engine blast when Eagle lifted off.

Why the footprints last

The Moon has almost no air, so there is no wind or rain to wear footprints away. That is why the boot prints at Tranquility Base can stay for a very long time. On Earth, a footprint in beach sand can vanish with the next wave or gust of wind. On the Moon, the fine gray dust simply keeps its shape, so the tracks the astronauts made while setting up experiments and collecting rocks are still lying where they left them.

On the 3D Moon

On the 3D Moon you can see Tranquility Base with the lander's lower stage and the laser mirror, and the flag lying where the engine blast knocked it over.