On July 20 astronauts Neil A. Armstrong and Edwin E. "Buzz" Aldrin and the Lunar Module Eagle touched down at the Moon's Sea of Tranquility. Emerging from Eagle astronauts Armstrong and Aldrin explored the surface for 2 hours 32 minutes, as Michael Collins remained in lunar orbit inside the command module. During this exploration, they deployed two experiments as part of the Early Apollo Scientific Experiment Package and collected 21 kilograms (46 pounds) of lunar samples for return to Earth.

Transposition and Docking

The Lunar Module (LM) was launched from Earth in a compartment of the Saturn V, below the command and service modules. Once the spacecraft were on their trajectory toward the Moon, the command module pulled the LM from its compartment, and the two traveled together until they orbited the Moon. The astronauts lived in the command module.

Because lunar modules were designed to fly only in the vacuum of space, they did not have to be streamlined like an aircraft or carry a heat shield for protection during reentry. They were built to be left on the moon. Once a lunar module was launched into space, it could not return to Earth.