The Eagle has landed: 11 amazing facts about Apollo 11

When Neil Armstrong made the first step onto the moon's surface, he had a prepared line... and it sounded like he messed it up. He said, "One small step for man," but he was supposed to say, "One small step for a man, one giant leap for mankind."

He later insisted that the "a" simply didn't get heard. In a 2006 biography, he noted, "I think that reasonable people will realise that I didn't intentionally make an inane statement and that certainly the 'a' was intended, because that's the only way the statement makes any sense."

Famous images show Neil Armstrong and Buzz Aldrin standing next to the American flag, the first flag planted on the moon. However, the flag is no longer standing proudly.

As the astronauts departed the moon, Buzz Aldrin saw the flag knocked over by the module's thrusters. It has since probably disintegrated under the moon's harsh conditions.

A few minutes after Buzz Aldrin and Neil Armstrong landed on the moon (fellow Apollo 11 astronaut Michael Collins remained in orbit), they sent a message back asking for a moment's silence. In this time, Aldrin, an elder in his local Presbyterian Church, had a little communion ceremony of his own, reading scripture and taking the sacrament.

In his own words: "I ate the tiny Host and swallowed the wine. I gave thanks for the intelligence and spirit that had brought two young pilots to the Sea of Tranquility. It was interesting for me to think: The very first liquid ever poured on the moon, and the very first food eaten there, were the communion elements."

Along with the American flag, the Apollo 11 mission left behind a small collection of items. Among them were medallions honouring Russian cosmonauts Yuri Gagarin, the first man in space, and Vladimir Komarov, both of whom died tragically. Komarov's death is particularly shocking. The story goes that he knew he was probably going to die on the 1967 mission to put a man into Earth orbit. He didn't back out, because Gagarin was his back-up and he didn't want Gagarin to die.

When attempting to land the Apollo Lunar Module (also called the Eagle), pilot Neil Armstrong had to think fast when they missed the landing site and were aimed at not an obstacle-free plain, but a crater. He piloted the craft even farther from the landing site, and descended to the surface of the moon four miles from the original landing site with less than a minute of descent fuel remaining.

"The Eagle has landed." The phrase is famous, but they weren't the first words spoken from the surface of the moon. According to the mission transcript, the first words were "contact light," spoken by Buzz Aldrin as the Apollo Lunar Module's probes touched the surface of the moon, followed by a brief checklist before Armstrong spoke the famous words.

The three astronauts were in very close quarters during the eight-day mission. This would normally be a little rough, but it was made even worse by the water.

"The drinking water is laced with hydrogen bubbles (a consequence of fuel-cell technology which demonstrates that H2 and O join imperfectly to form H2O)," wrote Michael Collins in a 2001 memoir. "These bubbles produced gross flatulence in the lower bowel, resulting in a not-so-subtle and pervasive aroma which reminds me of a mixture of wet dog and marsh gas."

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."

On their return to Earth, the three astronauts were brought back via Hawaii. On their entry, they had to be processed like any other traveller, filling out customs declarations. In the "Departure From" field, they simply wrote "Moon," and declared the "moon dust" and "moon rock" they were bringing into America.

Life insurance premiums for a trip to the moon were well beyond the means of Armstrong, Aldrin and Collins. As a preemptive measure to take care of their loved ones if they didn't come back, the astronauts signed hundreds of postal covers. If they did not return, their families could sell these signatures. Today, these signed postal covers occasionally show up in space memorabilia auctions, where they can sell for thousands of dollars.

President Richard Nixon had a contingency speech lined up for if the mission failed, too. You can read it here.

When Armstrong and Aldrin returned to the Eagle from mucking about on the moon, they were able to smell the moon dust on their space suits. In his 2009 memoir "Magnificent Desolation," Aldrin described it as "a pungent metallic smell, something like gunpowder, or the smell in the air after a firecracker has gone off." Armstrong, as noted in the 2001 book "Tracking Apollo to the Moon," described it as "wet ashes in a fireplace."