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It’s been over 50 years since the Apollo 11 mission landed humans on the moon, and in that time, we’ve learned a lot more about what happened during that historic event.

Here are five facts that you may not have known about that historic mission that began on July 16, 1969:

1. NASA was worried about moon germs

Following their arrival from the moon on July 27, 1969, Apollo 11 astronauts Neil Armstrong, Buzz Aldrin and Michael Collins were forced to quarantine for over two weeks in case they had returned with any dangerous lunar microorganisms.

Immediately after returning to Earth, the astronauts were transferred into a modified Airstream trailer with a physician and a technician. The “Mobile Quarantine Facility” was transported from the USS Hornet to Pearl Harbor. It was then loaded onto a military transport aircraft and flown from Hawaii to Houston.

The astronauts spent the remainder of their quarantine in the NASA Lunar Receiving Laboratory at Johnson Space Center.

On Aug. 10, 21 days after landing on the moon, Armstrong, Aldrin, and Collins stepped out of quarantine to a room full of reporters.

2. Pieces of The Wright Brothers’ “Wright Flyer” went to the moon (and back)

According to The Associated Press, a fragment of wood and piece of muslin fabric from the 1903 Wright Flyer flew to the moon with Apollo 11′s Neil Armstrong in 1969. The fabric and wood are displayed at the National Air and Space Museum in Washington, D.C.

3. The crew was afraid of being locked out of the lunar module

After Armstrong made his first steps on the moon, Aldrin was cautious as he exited the lunar module. He was concerned that the lander would automatically pressurize if the door was latched. Because the hatch opened inward, the pressure inside the lunar module would have made it impossible to open from the outside.

“I then got in position to come down … came down the ladder, and jumped off, being careful not to lock the door behind me,” Aldrin recounted in a Reuters interview.

4. A felt-tip pen kept them from being stranded on the Moon

After the historic moonwalk on July 20, 1969, Armstrong and Aldrin were preparing the lunar module for the return to the orbiting command module when they noticed a broken circuit breaker on the floor.

According to, the broken piece was part of an engine arm circuit breaker that had broken off the instrument panel, likely by their backpacks. Without a fix, the two would be stranded on the moon.

In his book, “Magnificent Desolation: The Long Journey Home from the Moon,” Aldrin described how they solved the problem using a felt-tip pen.

“After examining it more closely, I thought that if I could find something in the LM to push into the circuit, it might hold. But since it was electrical, I decided not to put my finger in, or use anything that had metal on the end. I had a felt-tipped pen in the shoulder pocket of my suit that might do the job,” Aldrin wrote.

Aldrin inserted the pen in the panel, holding the circuit breaker in place. The pair lifted off the moon not long after.

“To this day I still have the broken circuit breaker switch and the felt-tipped pen I used to ignite our engines,” Aldrin wrote.

5. Astronaut life insurance

Because of the risk involved with spaceflight, the three astronauts devised a clever way to provide for their families in case they didn’t return —autographs.

In the weeks leading up to liftoff, the astronauts signed as many autographs as they could in every spare moment, according to NPR. The astronauts signed hundreds of envelopes to be later postmarked and distributed to their families.

“If they did not return from the moon, their families could sell them — to not just fund their day-to-day lives, but also fund their kids’ college education and other life needs,” space historian Robert Pearlman told NPR.