In 2011, I discovered for myself just how altering that experience can be when a small aircraft dropped me on the coast of Antarctica at the beginning of a two-month journey to ski across the continent alone.
As the plane slowly vanished I took in my surroundings. On one side was the flat white horizon of the Ross Ice Shelf and on the other the distant peaks of the Transantarctic Mountains. I knew that in all that landscape I was the only human being -- but quite possibly the only form of life whatsoever. Away from the open water 700km (435 miles) to my north, there was no wildlife -- no penguins or seals, no moss or grasses. Just me.
More significantly, I knew that it had taken two planes, two fuel depots and more than a week of complex logistics to get me to my start point. There was no chance of the plane easily coming back for me.
Out of habit, I immediately fell into my familiar expedition routine, preparing my kit in order to begin skiing the following day. But as I worked I noticed that something was wrong. My heart was beating fast. I was unusually clumsy. My hands were visibly shaking. Abruptly, I realised what the problem was -- I was terrified. Not terrified of personal injury, or of the risk of fatality in the weeks and miles to come but terrified of being so utterly isolated.
It was the alone-ness itself that was frightening and my subsequent 59-day ski across the continent was dominated by my battle to deal with the shock of it.
I imagine that the first humans to visit Mars might experience a similar state of shock at their disconnection from human society. It is intriguing to wonder whether there might be parallels between the psychology involved in exploring Mars and exploring Antarctica.
Could potential astronauts preparing for long space missions across the solar system learn anything useful from experiences like mine in Antarctica?
As I began my loneliest of expeditions I had the benefit of more than a decade of previous polar journeys to draw from. In addition I had carefully prepared for the psychological stress of isolation, consulting a specialist sport psychologist.
Yet, I was taken aback by the range of ways in which the alone-ness affected me. I became increasingly emotional. With no one to witness my behaviour, I allowed inner feelings to flow into outward expression without check. If I felt angry, I shouted. If I felt upset, I cried.
Self-discipline became much harder. Surrounded by others, taking risky short-cuts isn't a possibility, largely because of the embarrassment of being discovered. But alone, with no-one to observe your laziness, the voice of temptation was always present. I found that ignoring the voice of temptation was an extra drain on mental energy that simply hadn't existed on team expeditions.
My brain, starved of any input by the lack of colour, shape or form in my largely blizzard-obscured world began to fill in the gaps by creating hallucinations.
I was surprised to find that we can hallucinate not just with our visual sense but with all our senses. I hallucinated strange forms in the gloom of regular whiteouts that took the shape of floating hands and small bald men on dinosaurs, but I also hallucinated smells, tastes and sounds that all seemed very real.
As I skied, I began to direct my internal monologue at the sun (when it was visible through the bad weather) and was slightly perturbed when eventually the sun began to talk back to me in my mind. It took on a very distinct character and even though I knew on some level that it wasn't real, the sun played an important part in my coping strategies.
Routine became increasingly important to me in overcoming these damaging responses to alone-ness. When everything else in my landscape and daily experience was so surreal, routine became the rhythm that I clung to. I performed every task in exactly the same way, every time it had to be done. I repeated chores in the same order again and again until I reached the point that I barely had to think about them. Reducing the thought required seemed to simultaneously reduce the emotion.
This was despite the fact that I did have some connection to the outside world during my expedition. I carried a satellite phone which was capable of calling anyone in the world at any time from my tent -- and yet, largely, I decided not to.
I was scared of the emotional high that speaking to loved ones might bring, knowing that it would inevitably be followed by a crushing emotional low as I was forced to end the call.
The one call I was obliged to make every day to a logistical coordinator in Antarctica to report my position became nothing more than a brusque transfer of information. I simply couldn't cope with the emotional entanglement of even the briefest of conversations. The switch between complete isolation and sudden connection with another human being was too much for me to process emotionally.
And that, perhaps, is the most important advice I could offer potential interplanetary astronauts -- to prepare not just for the psychological response to their undertaking, but the emotional response too.
I would speculate that their preparations need to allow for an emotional response to the enormity of what they are doing, the complexity of the expectation from home and the strangeness of their normality. We humans are emotional beings, which means that we often react in illogical and unexpected ways.
Any preparation for long interstellar missions would be all the stronger for taking that into account.
And by the way, despite all the challenges of my time alone in Antarctica, if there are any spaces left on that mission to Mars ... I'd love to apply.