Apollo 11 Mission Overview
Left: Lunar Module Pilot Buzz Aldrin. Commander Neil Armstrong, who took the photo, and the Lunar Module Eagle are visible as reflections in Aldrin’s helmet visor. Right: Aldrin’s bootprint in the lunar regolith.
Apollo 11 was launched on July 16, 1969, at 8:32 AM Central Daylight Time (CDT) with the goal of performing the first human landing on the Moon. Commander Neil Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Edwin “Buzz” Aldrin entered lunar orbit on the afternoon of July 19. The following day, Armstrong and Aldrin begin their descent to the lunar surface in the Lunar Module, Eagle. The planned landing site in the Sea of Tranquility was selected as a flat, safe location and had been surveyed by Apollo 10 at an elevation of 10 miles above the Moon. However, a navigation error earlier in the mission caused Eagle to be about 7 kilometers beyond the planned landing location.
During the 12.6-minute-long powered descent, there were a total of five unexpected computer alarms. These alarms all indicated that Eagle’s computer system was overloaded, but in each case, Mission Control concluded that it was safe to continue the landing. The last of these alarms occurred less than three minutes before landing, when the crew was less than 500 meters above the surface. Because of the navigation error, the computer was guiding the spacecraft towards an unsafe touchdown point in the rugged, boulder-filled ejecta field surrounding West Crater. Armstrong took manual control and flew to a safe landing spot beyond the crater. At 3:17 PM CDT, he announced their safe landing, “Houston, Tranquility Base. The Eagle has landed.” At the time of landing, Mission Control thought that the spacecraft had just 17 seconds of fuel left in the descent stage. However, post mission analysis showed that sloshing in the fuel tank during Armstrong’s search for a safe landing site caused the fuel gauge to give an inaccurate reading. Eagle actually had about 45 seconds of fuel left when it touched down.
After a checkout of Eagle’s systems, Armstrong and Aldrin prepared for their moonwalk. At 9:56 PM CDT, Armstrong set foot on the lunar surface, “That’s one small step for man, one giant leap for mankind.” Aldrin followed a short while later. The duration of this first ever moonwalk was limited to just 2 hours and 31 minutes and the crew remained within 60 meters of Eagle. Armstrong and Aldrin collected 21.6 kilograms of samples and deployed a seismometer to measure moonquakes, a laser retroreflector to enable precise measurements of the distance between Earth and the Moon, and a device to collect a sample of the solar wind. They also performed ceremonial duties, including setting up a United States flag, unveiling a commemorative plaque on the lunar module, and having a brief conversation with President Richard Nixon.
During the moon landing, Collins remained in lunar orbit in the command module, Columbia. After just 21.6 hours on the Moon, Eagle’s ascent stage returned to lunar orbit and rejoined Columbia. Altogether, Apollo 11 spent 2.5 days in lunar orbit, circling the Moon 31 times. The crew returned safely to Earth on July 24, landing in the Pacific Ocean southwest of Hawaii, after a flight of 8 days and 3 hours. Although scientists considered it unlikely that the Moon had life on it, the crew was kept in a biological quarantine for 21 days.
Post-mission analysis showed that the Apollo 11 samples consisted of two primary rock types. Basalt is formed by the solidification of molten magma. The Apollo 11 basalts formed 3.6 to 3.9 billion years ago and are unusually rich in the element titanium. Breccias are composed of fragments of other rocks. On the Moon, breccias formed from rocks that are broken up by impacting objects. Analysis of the lunar samples also confirmed that they were indeed lifeless and showed no evidence of water.