The two returned to the command module in an ascent vehicle, which was later jettisoned, and they came back to Earth in the command module. The mission lasted from launch on July 16 to splashdown July 24.
The Smithsonian has had the command module since 1971, said Allan Needell, who is curator in the Air and Space Museum's division of space history and oversees the Apollo program collection.
The scan shows an interior crammed with switches, buttons and dials, as well as three side-by-side seats.
The astronauts' wall writings have been known to historians but have not been widely available to scholars and the public, Needell said Wednesday.
He said the calendar, which Collins kept, was perhaps helpful because the astronauts, lacking sunrises and sunsets, wanted to keep track of the days back on Earth.
The markings give a sense of reality to the module.
"The whole wonderful thing about this is . . . because the thing is dirty and marked up and obviously lived in, it gives you a way to sort of transport yourself into the context of an artifact that . . . we don't usually provide," Needell said.
Because of its importance, he said, experts have been careful not to venture often inside the fragile command module. But the chance to scan inside would provide researchers a detailed record of life on board.
Amid the drama of the mission, for example, "it got pretty stinky in there," he said.
"There were various human functions that went on," he said. "Once they closed up some smelly waste in some locker, they didn't really want to bother to open it again until they were home."
So they labeled lockers accordingly.
Needell said the command module will be removed for conservation next year so it can be included in a future state-of-the-art gallery at the museum. The Smithsonian said the new exhibit is scheduled to open in 2020 and is titled "Destination Moon."