Ever since the official announcement by Dennis Tito that he is planning a privately financed manned Mars flyby in 2018, whenever I catch a glimpse of the SpaceX capsule on television or on the Internet, my heart beats just a little faster.

That is because, for just a fleeting moment, I imagined what it would be like if it were my wife and I who took this planned 501-day trip. And when I did that, suddenly all the excitement I used to feel reading science-fiction as a young teenager came back. Heck, my heart beats faster even now, as I am writing down these words.

I imagined the work preceding the launch. The astronauts of this mission will do a great many things that have never been done before. First, they will spend 501 days in space; the longest mission to date was 438 days. They will spend most of this time far from the Earth, with no abort option, and no help available. In other words, whatever happens during these 501 days, they will be on their own. Which means that in the years leading up to launch date, they will need to learn everything. They will need to be able to disassemble, repair, and reassemble the spacecraft's systems in their sleep. They will need to acquire a basic level of medical knowledge sufficient to provide help to each other in case of a serious medical emergency. The learning they will need to do... well, let's just say 2018 is not that far away, and if Mr. Tito & Co. are serious, they better start crew selection soon.

I imagined the days just before launch. When the rocket is already assembled, "all systems go", the last media interviews are done. The worry over last minute concerns, the knowledge that if something goes wrong and the launch window is missed, all those years of preparation will have been for naught.

I imagined launch day. When you ride the elevator up to the capsule and look around one more time, with the knowledge that if all goes well, this will be the last time you are going to see a blue sky in person for the next 17 months or so; and if things don't go so well, this is the last time, period. You say good-bye to the launch crew and then you look at each other, knowing that the face in front of you will be the only human face you will see for the next year and a half.

I imagined the launch itself: ten minutes of terror, as the equivalent of a small nuclear explosion takes place under your hind part in a controlled manner, accelerating your capsule to escape velocity and beyond.

And then, I imagined the days that followed. They are likely to be very busy days: deploying the inflatable crew habitat, rearranging the furniture, and dealing with the inevitable glitches of all the equipment designed to keep two humans alive in deep space for 501 days. But there will be time to think, to look out the windows, to reflect. Not long after launch (a day, maybe? Perhaps less? It took Apollo four days to get to the Moon but that was a completely different trajectory) the spacecraft will cross lunar orbit, and you two officially break the record of traveling the farthest from our home planet. And not long after that, it becomes impossible to hold a meaningful conversation over the radio, due to delays. Same goes for conventional Internet connections; no more simple browsing the Web.

And, as you settle into the daily routine, the Earth keeps shrinking in the window, until one morning you look out and realize that your eye can no longer resolve it into a disk: the Earth has become a star. Sure, it's still the brightest star in the sky (its companion the Moon, the second brightest) but... just a star. No matter where you look, the only object outside of your spacecraft that is not a pinpoint of light is the Sun (and you better not look at it directly, especially in deep space). You are truly and utterly alone.

Meanwhile, the spacecraft begins to stink a little. Your drinking water is recirculated urine. Toilet cleaning in zero-G is no fun. There are inevitable breakdowns and glitches that require hours of painful work; you cannot afford to make a mistake, since these are largely non-redundant systems and your lives depend on them. There is no turning around. And it's a tad noisy: machinery runs all the time, processing your air, maintaining the temperature, processing your waste. Fortunately, none of this is unexpected: you knew exactly what you signed up for.

And the trip goes on and on and on, in deep space, much like the serene scenes from 2001: A Space Odyssey. You may even feel inclined to listen to Blue Danube by Johann Strauss, not because you like 19th century pop music but because, well, Stanley Kubrick was right: it is appropriate for the occasion.

And the months go by. The Earth now faded. It remains the brightest star in the sky, but it is now simply a bright star, nothing more. The Sun continues to shine of course, and you hope that that's all it does; a solar flare in your direction might flood the spacecraft with a deadly dose of radiation. Your shielding is inadequate as it is; when you signed up for this mission, you did so in full knowledge of the fact that your lifetime risk of cancer will be much greater upon your return. But a solar flare would kill you a lot more quickly.

And the months go by, and you now have a new brightest star in the sky, and it is red. You stare at it every day. You already know the features of the Red Planet by heart, and as you stare at that ever brighter dot, you imagine that you can already resolve the southern highlands. Until one morning, you really can. Well, sort of... you cannot really see surface features just yet, but you can definitely see the disk of Mars with your naked eye.

Things speed up a great deal around this time. Thrusters that have not been used for months come to life to make last-minute course corrections. I imagine that the inflatable module will be deflated and stowed, to make sure that it is not damaged as your spacecraft skirts by the planet's upper atmosphere. The excitement grows.

And the big day comes. Mars now looms big in the sky, and you realize that you can actually see it grow slowly. You get closer and closer. Taking only short breaks, you two give an on-going commentary over the radio to a terrestrial audience that may number in the billions. The hours tick by and Mars fills the sky. Suddenly, you no longer feel like being in a spacecraft; you are flying over the surface of an alien planet. With a small telescope, you can see rocks1. You remind your audience that it was just 50 years earlier that a human being set foot on Earth's satellite, traveling less than 400,000 kilometers; and now here you are, several ten million kilometers from your home planet, flying by an alien world. An alien world that one day... well, you are not in it for the glory, but you know that if humans ever colonize Mars, there will be metropolises on the planet named after you.

And then, it's all over. Mars begins to recede in the distance. You end your live radio broadcast (well, "live", although it took some 7-8 minutes for the signal to reach the Earth) and take turns using the zero-G toilet.

The flyby is over but the trip isn't. You still have another eight months and then some to go. You are in deep space again; Mars rapidly shrinks back to the bright red dot that it was for most of your trip on the way there. But your eyes are now set on the Earth.

You of course get the news coverage. You know what Earthlings think and say about your historic trip. You also get other news: news about suffering, about conflict, about wars. You send back messages, accompanied by pictures in which the Earth is just a bright point of light in a jet black sky, about peace and unity. About how unimportant such petty conflicts are when the entire planet, with all the billions of souls that live on it, is just a speck of dust in the sky. You utter messages of peace in English, Arabic, Chinese, and other languages. You appeal to God, Jehovah, Allah and other deities. And you know that it will be in vain; conflicts and suffering will not end just because of this one inspiring trip. But you still feel compelled to do this.

And the months go by. The Earth is now dominating the sky: it is still just a star, but a really bright one, and you can see its companion the Moon, too. The radio delay is becoming shorter.

And then only days are left. Final course corrections have been made, you know the exact moment and location of your atmospheric entry. As do the captains of the fleet who will recover you from the ocean. You are making final preparations. Some things remain in the inflatable habitat; other things need to be hauled back into the capsule. A day or so to go, and the passageway is closed, the habitat is detached. It will burn up in the atmosphere.

And then come the final few minutes of terror: the capsule enters the atmosphere. Its heavy duty heat shield, never tested in flight, is what keeps you from burning into cinders. The force of gravity is almost unbearable; you just spent a year and a half in deep space with less opportunity to exercise than the cosmonauts of Mir. Herds of elephants are sitting on your chests. Then the pressure eases... but it never quite goes away. Explosive bolts do their business, the parachutes open and your spacecraft is now gently floating down towards the ocean, with the ships rapidly closing in on your anticipated impact point.

Splash! You are down. Everything worked as they were supposed to. You wouldn't be here otherwise; there was absolutely no room for error. You are bobbing up and down. You feel nauseated, and the pressure of 1g gravity is nearly unbearable. You know that you won't be able to get out of your couches without help, but this, too, is not unexpected. Finally, the recovery crew arrives, they attach the capsule and lift it out of the water, and that's it: your journey is over. You are removed from the capsule and taken onto gurneys, since you are unable to stand up and walk in the Earth's gravity; it will be a few days (a few very hard days) before you are able to stand on your own feet again.

But that day, too, will come, perhaps too soon. Because these will be the days when you will do more miles in ordinary aircraft than the length of your trip to Mars. You will meet kings and queens, presidents and prime ministers, the Pope and emperors. You will talk publicly about what it was like to be out there in deep space and why it is so important for humans to be out there. The moments you will most enjoy is when you talk to school age children seeing in their eyes the dream that one day they will be the ones who walk on Mars, but what you will really long for is privacy. You will wish to be back on the spacecraft, halfway between the Earth and Mars.

But then this, too, will fade. The world's attention will turn elsewhere. You get fewer invitations and it will be easier to turn them down. You still have a PR manager, but you no longer talk to her several times each day. Eventually, you can return to a more or less private life and reflect upon what you did. You will worry about your health: cancer screening will be a routine part of your medical checkup for the rest of your lives. You will start writing your memoirs. You will try to find new meaning for your lives even as you know that nothing you do will ever top what you have done. But this, too, was part of the deal; you knew this was bound to happen when you signed up.

And if you are lucky, your marriage will have survived the trip. It's not easy even for a loving couple with a 20-year marriage behind them to be locked up in a tiny capsule for a year and a half, but you managed, and you are still together. You step out onto your balcony one night when Mars is high up in the sky, look at it and while you hold hands, you tell each other: we have been there. After billions of years of life, millions of years of human evolution and thousands of years of human civilization, this species acquired the ability to build machines that could haul two human beings across such an unimaginable distance, to fly by another planet. And you two were those two human beings.

And you realize that even if you are diagnosed with cancer the next day, even if you are bound to die a premature death in suffering and pain, it will have been well worth it.

You step back in, you close the balcony door. You feed the cats, make the bed and retire for the night, talking about the ailing air conditioner in the house that will soon need servicing, and about when to take the cat with the ingrown claw to the vet. You sleep soundly and wake up in the morning, just a few minutes before the alarm would go off, refreshed. And thus you begin the first day of the rest of your lives.

1 Or not; after I finished writing this article, I came across a diagram of the proposed orbit and realized that during closest approach, the spacecraft will actually be flying over the night side of Mars.