After a tense final descent in which Armstrong took manual control to avoid a boulder field, the Eagle landed with roughly 25 seconds of fuel left. Mission Control's Charlie Duke radioed the famous line acknowledging Armstrong's report: 'Houston, Tranquility Base here. The Eagle has landed.' Hours later, Armstrong became the first human to walk on the Moon.
The landing almost didn't happen the way anyone planned. As the lunar module Eagle descended, its computer flashed unfamiliar alarm codes—1202, then 1201—overloaded by unnecessary data from a rendezvous radar switch left in the wrong position. A 26-year-old guidance officer named Steve Bales, sitting at Mission Control, made the call in seconds to continue the descent, a decision for which he later received the Presidential Medal of Freedom.
Then Armstrong saw the actual landing site: a crater strewn with car-sized boulders, nothing like the smooth plain in the simulations. He took semi-manual control, flying Eagle horizontally across the surface searching for clear ground, burning precious fuel while Mission Control and Aldrin, calling out velocity and altitude numbers, waited in silence. Estimates afterward suggested as little as 17 seconds of fuel remained when contact light confirmed touchdown.
Six hours later, at 10:56 PM EDT, Armstrong climbed down the ladder and stepped onto the surface, telling a television audience of 600 million people, 'That's one small step for man, one giant leap for mankind.' Aldrin joined him 19 minutes later, describing the view as 'magnificent desolation.' They spent two and a half hours outside, collected 21.5 kilograms of lunar samples, and planted an American flag before returning to lunar orbit to rejoin Michael Collins.