Mars One will soon open the application process to be part of the first Mars colony in 2023, and it recently released the basic requirements to become a future member of this Red Planet community.

Are you at least 18 years old? Proceed. Do you have a "can-do" attitude? Keep reading. Are you in good physical health? Check.

Are you willing to spend the rest of your life on Mars without the possibility of returning to Earth? Pause. Re-read that sentence. Your future home on Mars is permanent, and understanding that is the most important criteria of an applicant.

"Once on Mars, there is no means to return to Earth. Mars is home. A grounded, deep sense of purpose will help each astronaut maintain his or her psychological stability and focus as they work together toward a shared and better future. Mars One cannot stress enough the importance of an applicant's capacity for self-reflection."

This isn't the first we've heard of colonizing Mars without the possibility of return. In fact George Herbert first introduced the concept in 1990 with a plan called "Mars to Stay." It proposed sending astronauts on a one-way mission to Mars to avoid the technological hiccups and costs associated with launching a return flight.

Mars One, a non-profit venture based in the Netherlands, is headed up by Dutch entrepreneur Bas Lansdorp. It plans to launch at least six groups of four people that will spend at least five years training together before launch. Every two years, another team of colonists will settle on Mars, adding to the overall population.

Other private Mars colonization projects — Mars Society and 4Frontiers are just two examples — operate under a similar lofty plan, with some minor differences. And these movements have their share of big-name supporters, including former astronaut Buzz Aldrin.

Even with a one-way flight, however, many political and technological concerns remain. When it comes to putting a man on Mars — let alone letting him live out his life there — some of the greatest minds in science remain divided on the subject.

Our Brains Are a Big Hurdle

Let's assume the technology exists (Mars One and other similar ventures say it does; other experts say it will take longer) and that the funding is there (Mars One estimates it will cost $6 billion. Meanwhile, NASA says it's hard to put a price on it, but for reference, the highly sophisticated Curiosity rover cost $2.5 billion.).

Even if all these seemingly unreachable factors fall into place, there still remains one basic problem that we'll never be able to control: human nature.

Aside from the unknown physical health risks associated with living with 40% gravity, could we psychologically handle Mars without return? That's the question we wanted answered, and it's one that Mars colony supporters don't tend to address. Isolation and depression will be these colonists' darkest demons.

A few years ago, NASA put together a wildly imaginative plan for a round-trip manned mission to Mars. According to this report, one of the key challenges for a mission like this is behavior and performance deterioration during long-term spaceflight missions — and that's for astronauts who will actually return to Earth.

The study points out that "humans have never embarked upon spaceflight missions approaching the scale of exploration now envisioned." So far, the best research that we have regarding this type of isolation comes from Antarctic and undersea expeditions.

Marc Shepanek, lead for aerospace medicine at NASA, has been on one of these Antarctic missions himself. "I prepared for the vast majority of things that I was going to experience," he explains. "I had the benefit of having worked at NSF, working with people who had worked down South. I was very well-read, even for the research I helped report when I went down."

Despite months of training, heavy gear, knowing — and mentally absorbing — the fact that there would be a 90-degree drop in temperature, Shepanek didn't really understand the Arctic until he first stuck his head out the window. "My face hurt from the drop of temperature [...] then it fully registered with me."

"I imagine the first time an astronaut experiences micro-gravity, sees the earth from that great height — no matter how much you have read, no matter how many pictures you have seen — I imagine that it's an experience," he says. "Being human beings — even the most controlled, disciplined, capable human beings — it's going to be different when you do it."

Shepanek does say humans are easily trained when it comes to social skills, and that includes mentally preparing for an extended period of isolation.

Mars One Medical Director Norbert Kraft agrees that no one can really understand how an isolated life on another planet will really affect them until they are actually there — of course by then it's too late.

Prepping for a Mission Without Return

Kraft says Mars One will do its best to prepare these pioneers with ten years of training that includes spending three months of every year inside an isolated habitat. "Then we will see if they can handle that environment," Kraft tells Mashable. "It's tough for someone to imagine that environment. You have to experience it to know if you're the person that can do this."

Even NASA has trouble assessing astronauts for long-term missions. During selection for a mission of this kind, applicants identified with a psychiatric disorder that would impede on-the-job success are removed from further consideration. As a result, some astronauts hide preexisting psychological conditions that could jeopardize their flight status.

"If someone were to go [into space] and something were to happen, there are regular private psychological conferences every two weeks and more frequent on a long term mission," Shepanek says. "You can always request a private conference, and you always have access to a crew medical officer that's on board every mission."

However, even successful precautionary measures doesn't necessarily guarantee a healthy crew. The average age of onset depression for people who have no family history of depression is 41 years old. Astronauts selected for the Astronaut Corps can be as young as 26. Mars One will consider applicants as young as 18; those participants would be 28 when they land on Mars.

The European Space Agency recently conducted a Mars mission simulation in which six volunteers were locked inside a spaceship for an unprecedented 520 days, making it the longest spaceflight or simulation in history. The results? The crew's overall movement progressively decreased, entering what the researchers called "behavioral torpor." They also experienced notable disturbances in sleep behavior.

"Five of six crew members slept more, and it is usually sleep deprivation that is linked to depressive symptoms. [Of the six] only one crew member showed signs of (self-reported) depressive symptoms," says Mathias Basner, study co-author and assistant professor of Sleep and Chronobiology at University of Pennsylvania.

Basner says insufficient light in the chamber may have contributed to the depressive symptoms in the crew member. A Mars colonist would be subjected to similar indoor lighting conditions and confined spaces, but for an even longer period of time. When asked if, based on the information we currently have about Mars' environment, it's possible to predict how a human would psychologically react once he or she is there, Basner says "absolutely not."

"At this point, it is pure speculation, he says. "The partial gravity and a longer than 24 hour day alone will be very challenging."

Who Gets to Live on Mars

Mars One has already received more than 1,000 emails from people interested in this mission, and the application process hasn't even started yet. But how will Mars One — or any Mars colonization project for that matter — whittle down the applicants into a small group of serious people in which private investors will pour billions?

When assessing potential astronauts, NASA not only applies the rigorous background checks that come standard with government jobs, but the agency also puts its candidates through various physical tests and extensive interviews with both psychologists and psychiatrists.

However, Mars One's selection process is quite different. Certified physicians and scientists with years of experience will not select the future Mars colonists — you will. The public will choose the candidates who make it to the final round after a televised gameshow-like reality competition.

There will be a national selection in which 20-40 applicants per country will participate in challenges "that demonstrate their suitability to become one of the first humans on Mars." This whole process will more than likely be broadcast on television, and the the audience will select the one applicant from their respective country that will move forward.

Mars One will still have the final say of who goes to Mars, and crew selection will also depend heavily on how the members get along with each other, a key interpersonal component NASA also looks for when assessing astronaut candidates.

"These people should be comfortable with being observed all the time," says Kraft. "They won't have a lot of privacy."

On paper, a future colonist's day on Mars sounds similar to the life we live on Earth — do a job for eight hours per day, after which they can go "home" to call family or watch television. But, in reality, it's more like an extraterrestrial version of The Truman Show — a life lived under surveillance.

Suicide Mission or Revolutionary Exploration?

Like the vast majority of federal space agency experts, Shepanek believes that a round-trip manned mission to Mars should precede Mars colonization. An extended stay on Mars "would be something to answer after we go for a short period of time," he says.

The astronauts' health is NASA's No. 1 priority, according to Shepanek. When it comes to putting a man on Mars to live, however, there just simply isn't enough information to guarantee that.

"Working for NASA and knowing astronauts as I do, I want to keep them healthy. If given a choice, we like to bring our people home," Shepanek explains. "It's not unlike the field — we leave no one behind. We will take care of health and safety no matter what. Failure is not an option."

Mars to Stay proponents, though, don't believe this one-way journey is a suicide mission. Its supporters point out that, historically, man has gone to the ends of the Earth without the promise of return in the name of exploration. Columbus, Frobisher and Scott embarked upon their missions at the expense of huge personal risks.

That notion of boundless exploration is one of the only things that both federal agency experts and Mars colony supporters can agree on when it comes to putting humans on the Red Planet.

"If the kings of Spain and England could send people around a world that was potentially flat, I couldn't imagine that we wouldn't be capable of going to Mars and coming back," says Shepanek. "People are flexible; they adapt. There are all kinds of people in history who have survived heroically [...] It's amazing what people can do when they have to."

Mashable composite/photo courtesy of NASA; Image of Mars colony courtesy of Mars One