NASA’s Apollo missions were the only instance in which human beings have successfully set foot on another world, an accomplishment that can’t be overstated and will likely continue to grow in importance as our civilization continues its reach toward the stars. Because of this, the experiences of the only 12 men to ever set foot on the Moon have been subject to a great deal of analysis and observation, as their adventures in space have provided the human race with a lens through which to witness just how small we truly are when juxtaposed beside the vastness of existence.

Plenty of people have opined on how Neil Armstrong must have come up with his famous lines before departing the Lunar Lander for the first time, and we all sat on the edges of our seats as we watched Tom Hanks recreate Jim Lovell’s anxiety in the face of disaster, but something we tend not to think much about are the less logical, emotional moments these men likely experienced. Armstrong’s eloquence and Lovell’s composure make for easy-to-understand—and to appreciate—moments in our species’ history, but it can be harder to grasp the sense of uneasiness, of fear, that likely wormed its way into the minds of NASA’s best and brightest.

I’m at my most comfortable when I’m alone, I prefer night over day, and I love the woods. Combine those elements, and you’d think you’ve got the recipe for a guy who would just adore roaming around the woods at night all by myself. It would be a fair guess, as I’ve certainly spent a lot of time alone in the woods at night, and you’d be hard-pressed to find a time in which I’d pass up an opportunity to do so again. The thing is, though, being alone in the woods at night can sometimes scare the living crap out of me, too.

Those creeping uncertainties about yourself, your environment, your ability to handle whatever may pop up around the next corner, are all exacerbated by unfamiliarity and discomfort. If you’re not familiar with the trail you’re on, being alone in the woods at night can legitimately be risky. If you’re 238,900 miles from home in a tin can, one might assume those nagging concerns wouldn’t have to try hard to find their way into your conscious mind.

This brings us to the picture at the top of this article, a picture I’m convinced is the scariest ever taken by our space program. It depicts the Apollo Lunar Lander in the distance, tiny and barely visible from the vantage point of our astronauts.

Eugene Cernan and Harrison Schmitt drove their lunar rover as far as 2.5 miles from the Lander that offered the only tiny bit of refuge from the lethality of space on the entire celestial body they inhabited. The two men, who were the only living things on a planet larger than Pluto, wandered the barren expanse of the lunar surface for nearly three days, all the while relying on their space suits and the external shell of the Lander, as thin as a single piece of aluminum foil in some places, to keep them alive.

This picture demonstrates the vastness of our moon, which we tend not to think of as that big at all, and how the most technologically advanced equipment the human race was capable of producing at the time amounted to little more than a tiny dot in the distance. If the batteries on their rover failed, it was highly likely the both Cernan and Schmitt would have died well before being able to reach their tiny bit of oxygenated shelter.

'In Event of Moon Disaster' - the White House memo to be used if Apollo 11's crew became stranded on the moon

Read Next: 'In Event of Moon Disaster' - the White House memo to be used if Apollo 11's crew became stranded on the moon

I can’t tell you how many times I’ve stepped out of my front door in the middle of the night, listening to the sounds of the forest and waiting for my eyes to adjust to the darkness, and felt an uneasy feeling wash over me. There, beyond my line of sight, was the unknown, where danger could feasibly be lurking. Now imagine that same sense of dread climbing into your mind while sitting there, miles from shelter, the only human beings in the world, and knowing full well that if something were to happen, there was no one coming to save you.

Being brave in a moment that demands it is, of course, heroic, but we shouldn’t lose sight of the steady, consistent courage it takes to venture so far off the beaten path, alone in a lethal world, with no idea what’s around the next corner. If you’re not so sure you’d be willing to venture out a few miles into the woods in the middle of the night, just imagine what it must have felt like to leave the habitable cocoon of the Lander to drive a few miles into a never-before-seen expanse of the Moon’s surface, knowing full well that any sort of failure would result in asphyxiating a half a million miles from the family that you love.

Speaking of family, here’s one more picture from the Apollo missions that doesn’t get mentioned or shown very often, but that eases the anxiety I begin to feel when even thinking about what those brave men went through: It’s of a picture of astronaut Charles Duke’s family. He left it on the Moon before departing at the end of Apollo 16, making his family portrait the only one anywhere on the entire celestial body.

On the back of the photo, Duke wrote, “This is the family of astronaut Charlie Duke from planet Earth who landed on the Moon on April 20, 1972.”

Duke’s gesture to his family, however unrelated, does quite a bit to answer my questions about astronauts steeling their nerves. How do you face the kind of uncertainty and fear our astronauts must have experienced before setting out on their historic missions? The same way our war-fighters do: by remembering who they’re doing it for.

Images courtesy of NASA