The Eagle has landed: 11 amazing facts about Apollo 11 - CNET

The astronauts all carried Duro-brand felt-tip pens (pictured is Michael Collins' pen), and if not for these the mission would not have made it home. In the cramped environment, someone had broken off the switch to the circuit breaker that activated the ascent engine. This is where Aldrin had a flash of ingenuity.

"Since it was electrical, I decided not to put my finger in, or use anything that had metal on the end," he wrote in his 2016 memoir "No Dream is Too High."

"I had a felt-tipped pen in the shoulder pocket of my suit that might do the job. After moving the countdown procedure up by a couple of hours in case it didn't work, I inserted the pen into the small opening where the circuit breaker switch should have been, and pushed it in; sure enough, the circuit breaker held. We were going to get off the moon, after all."