Fifty years ago, three astronauts traveled to the moon for the very first time. 

Every American — and likely most people around the world — can recognize much of the audio, video and photos from the mission. However, a lot went into the Apollo 11 mission that most people may not know.

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Here are five facts you may not have known about the Apollo 11 mission.

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1. President Richard Nixon had a heart-wrenching speech prepared if the Apollo 11 mission failed. 

A mission to the moon was very dangerous, and there was a real chance that the astronauts on Apollo 11 would not have made it home safely. One of the biggest fears, according to the Washington Post, was that the astronauts would land on the moon but would be unable to get back to the space capsule. Nixon's chief of staff instructed a speechwriter to draft a speech for the president to deliver if the worst happened, which was later shared in a memo titled "In the event of moon disaster," discovered by a Washington Post reporter in the 1990s. The memo is difficult to read, even 50 years later: it instructs Nixon to call the "widows-to-be" on the phone before delivering the speech and says the astronauts' death should be treated as a burial at sea.

Read the full text of the speech here. 

2. The astronauts had to declare their moon samples at customs upon their return.

Seriously. According to Aldrin, he and the other two astronauts on the mission had to declare their moon rock and moon dust samples when they landed off the coast of Honolulu. Everything about the customs form Aldrin shared on Twitter in 2015 is entertaining, but if you look closely, you'll see the form says, "Any other condition on board which may lead to the spread of disease: TO BE DETERMINED." 

Yes the#Apollo11 crew also signed customs forms. We brought back moon rocks & moon dust samples. Moon disease

— Buzz Aldrin (@TheRealBuzz)August 2, 2015

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3. Instead of life insurance, the astronauts signed postmarked envelopes their families could sell if they died.

A life insurance policy for the first men to travel to the moon wasn't exactly affordable, so in lieu of an insurance policy, Neil Armstrong, Aldrin and Michael Collins signed hundreds of envelopes while they were in pre-launch quarantine. Then, on important dates like the day they launched and the day they landed on the moon, friends mailed them through the post office so the envelopes had postmarks for those important dates, with the intention that these envelopes could be sold for a small fortune — enough to support their families if the mission went south. Fortunately, the envelopes were never needed. However, as you can imagine, a few of them have surfaced, and they sell for as much as $30,000.

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4. The moon smells. 

It doesn't smell bad, necessarily, but it does have a scent. Aldrin said is smells like charcoal "or similar to the ashes that are in a fireplace, especially if you sprinkle a little water on them." Other astronauts have also described the moon's distinct smell, which you can read more about here. Experts say that smell comes from broken minerals. 

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5. The astronauts nearly forgot to leave a symbol of peace that they brought along with them. 

According to The Conversation, Aldrin and Armstrong were so occupied with that whole first-men-on-the-moon thing, they nearly forgot to leave behind small silicone disk inscribed with microscopic messages from world leaders. The messages are full of hope — one of Armstrong's favorites included a message from the president of the Ivory Coast, who wrote that the astronauts should "turn towards our planet Earth and cry out how insignificant the problems which torture men are, when viewed from up there." Read more of the inscriptions here.

Here are some of the personal items the Apollo 11 astronauts took to the moon