Leila Zucker remembers the ping of her inbox that launched her on this quest.

From: Ron Zucker

Subject: I don’t WANT you to...

Dan Carey remembers the tears on his wife’s face when they discussed his outrageous plan. He wanted to land his name in the history books. She wanted to know: “You would leave me?”

Derrick Johnson remembers the moment a bartender asked, “Hey Derrick, how’s that Mars thing going?” He remembers his heart lurching. Right then, he was standing next to his new boyfriend. The boyfriend he hadn’t expected. The boyfriend who didn’t know that Derrick had spent his whole life striving for something bigger than himself, so he had signed up for the biggest something he’d ever heard of.

“What Mars thing?” the boyfriend asked.

Derrick stuttered and stumbled, trying to explain, as they all must have done, Leila and Dan and the 202,583 other people who had applied for this seemingly crazy thing, this life-ending thing, this trip to the planet Mars.

“Wait, I read about that,” the boyfriend said. “Isn’t that . . . ” he slowed, stressing each word.

“. . . a one-way trip?”

Timeline: The ambitious — some say too ambitious— Mars One plan

The name of the organization that could be the first to put humans on the Red Planet is Mars One. “One,” as in, yes, one-way. It will launch people into space, land them on Mars and attempt to keep them alive for the length of their natural lives — but it won’t be bringing them back.

One-way is cheaper, according to the entrepreneur, physicist and physician masterminding the Mars One project. One-way is more technologically feasible. One-way, they believe, can happen in the year 2024.

NASA has no public plans to attempt a human landing on Mars until the 2030s, and even then, it will certainly be NASA astronauts who take the trip.

So what the Dutch not-for-profit endeavor promised was groundbreaking: Anyone could apply. With a decade until takeoff, Mars One founders reasoned that they don’t need the most experienced, educated or credentialed astronauts. They need people — four for the first trip, and four every two years after that — who can psychologically handle spending the rest of their lives with only each other on a planet no human has ever set foot upon.

Then and now, the skeptics abound. Some say the technology to survive on Mars isn’t nearly where it needs to be. Some doubt they can raise the funds to do it. Some are convinced it’s all a scam. But no one can prove that the plan is impossible — and for thousands of people, that was enough to put their faith in it.

Mars One is nearing the end of its nearly two-year selection process to narrow more than 200,000 applicants into 24. Those candidates, broken into six teams of four people, will spend eight years training and preparing, while competing against each other to determine which group will leave for Mars first. To help fund the estimated $6 billion trip, their experiences will be broadcast on television. Today, 660 candidates remain in the running.

[Here’s what a successful application for a one-way trip to Mars looks like]

You might assume that these people must be some kind of crazy; that they must hate their lives or harbor a death wish. But interviews with 10 of them and application videos made by hundreds of others show a group of people who seem pretty normal. Incredibly ambitious, but sane. Sixty-three have PhDs, and 12 are physicians. They are lawyers, pilots, veterans and businessmen. They come from all over the world: Moscow, Madrid, Miami Beach. The youngest were 18 when they applied, and the oldest was 71.

They are people who want to leave a mark on our planet — by leaving our planet.

On Friday, they will learn if they have made the next cut, from 660 to 100.Until this week, the candidates have been able to wait and wonder with no immediate pressure to commit to leaving the planet.

But if they make it through to 100, things start to get serious. They will have to look at their lives and declare if they really want to keep going, if they really want to make it into the cadre of 24 who will abandon it all. Grass. Beaches. Rain. The slobber of their dogs. The voices of their parents. The smiles of their children. All of it, to live on Mars.

Derrick Michael Johnson, 29, is one of the 660 Mars One candidates still in the running to be one of the first people to take the trip to the planet. (Marvin Joseph/The Washington Post)

Johnson chose his iPod as the one item he couldn’t live without on Mars. He plays multiple instruments, including percussion and the flute. (Marvin Joseph/The Washington Post)

Derrick’s mom can pinpoint when his life became focused on achievement. After his parents’ divorce, and those years getting picked on because he was “not a roughy-toughy boy,” she says, he switched schools in the seventh grade. As if a 13-year-old could sense the power of a fresh start, everything changed.

“I think I had the mind-set at that point that I wanted things to be different,” he says now. “I knew there was so much more I could learn, so much further I can go, so much greater I could be, I wanted to push that bar as far as it would go.”

By high school, Derrick was one of the popular kids. He played soccer, ran track and became the drum major of the marching band. He was voted president of the student body. He told his mom he would make it into a four-year college far away from their home in Maryland, and he did. He told her he would become the drum major of the University of Florida marching band, and he did. When he graduated, he told her he would be mayor of D.C. one day.

“And if he wants to, he will,” she said.

But a few years out of college, Derrick had lost that focus. He was 27 and single, toiling away at a government contracting job. His office was in a run-down building in Arlington. The paperwork was boring. One day in April 2013, a co-worker called him into her office.

“You gotta see this,” she said. It was a story about Mars One. Derrick had never been that interested in space or engineering. But back in his office, with a Florida Gators flag on the wall, he was convinced this was his next move.

Within days, he wrote the essays. He picked out a gray vest and bow tie and filmed his application video — singing, to a tune of his own making: “Anything can happen if, you dream, and try then stick with it, I want to inspire young lives, to imagine dream and thrive!”

He told his mom. She rolled her eyes. He told his co-workers. “What if you meet someone?” one of them asked.

“I just don’t think that’s gonna happen,” he said.

Daniel Max Carey, 52, is a father, musician and data architect. (Marvin Joseph/The Washington Post)

If Carey makes it to the next round, he’ll have to decide if going to Mars is worth leaving his wife and two children. (Marvin Joseph/The Washington Post)

Daniel Carey met his wife in 1982 at Georgia Tech. He was president of the student theater. Anne was working the box office. He asked her out to a dessert place called The Dessert Place.

Anne knew all about Dan’s childhood dreams of going to space. How he watched the Apollo launches on TV. How he thought humans would have landed on Saturn by now. How he quickly found out how difficult it is to become a NASA astronaut.

He grew up to become a data architect instead, and she an accountant. They had two kids, a dog named Joss and a house in Annandale. Their bedroom is space-themed. Anne let Dan decorate it. He chose yellow paint and a red comforter. He filled the bookshelves with “Mars Up Close” and “Red Mars” and “The Case For Mars.” He pasted a giant “Star Trek” quote on the wall.

When he sat down at dinner and told his family he was going to apply for Mars One, they weren’t surprised or terribly worried. What would these Dutch scientists want with a 52-year-old tech guy with no real aerospace experience? It seemed like just another quirky dad thing.

And then he made it to the next round.

And then Anne was crying.

Had he thought about all he would miss?

“How do you ask someone who you love to give up something that is important to them?” she said. “And on the other hand, how can they love you if they are willing to leave you to go do this thing they are dreaming about?”

His 20-year-old son Jack thought about how quiet the dinner table would be.

His 22-year-old daughter Wendy thought about the time her father had dressed as Santa Claus for the whole neighborhood, so dedicated to making the children believe that he dyed his eyebrows white. She had imagined him doing that for her own children one day.

Dan thought about those things, too. And he thought about Mars. He believed it was mankind’s destiny to explore the universe, that their mission would inspire generations to come. If Mars One decided that out of more than 200,000 people, he, Daniel Carey, has what it takes — the dedication to a team and capability for isolation, the smarts and skills and sensibility to survive on Mars — didn’t he have an obligation to go?

Leila Zucker, 46, says she would bring her husband, Ron, to Mars if she could. (Marvin Joseph/The Washington Post)

Zucker is one of 12 physicians still in the running to go to Mars. She holds the pieces to Looney Pyramids, one of her favorite board games. (Marvin Joseph/The Washington Post)

From: Ron Zucker

Subject: I don’t WANT you to. . .

but I’d feel like a lousy husband if I knew about this and didn’t at least send you a link.

Leila Zucker clicked, and there was her future in an NBC News headline: “Wanted: Astronauts for one-way trip to Mars.”

She knew why her husband had sent this to her. She wouldn’t have to explain it to him like she would to so many others.

“People ask, ‘Why would you want to go?’ But I see the reverse. Why wouldn’t I want to go?” she says. “People ask, ‘Well, what if you die?’ Well, I could die getting hit by a car tomorrow. I could die of old age. Or, I could die trying to be the first human to set foot on Mars. Why wouldn’t I want that?”

But of course, there are reasons not to want that.

Her job: She told her father at age 3 that she wanted to be a doctor. She applied to medical school three times before she was accepted into Georgetown at 35. Now, she is an emergency room physician at Howard University Hospital, where she gets to play the hero every day. She has, she says, the perfect job.

Her house: She loves this house. It is gray on the outside and sky blue on the inside. It has hardwood floors and a kitchen for Ron to make soup and an impressive collection of tabletop board games. It has no room for kids, and they plan on keeping it that way.

And her husband: A man who once quit his dream job in D.C. so she could move to California to care for her mother. Who moved back to D.C. so she could become a physician. Who sent her the Mars One application because he knew that her perfect job and her perfect house are just stuff. That’s what makes him the perfect husband.

The day her video interview with Mars One was scheduled, she thought about her answer to “Why would you want to go?” Norbert Kraft, the chief medical officer of the organization who was conducting the interviews, was bound to ask something like that.

She looked into the camera, and he popped up on the screen.

“Hello, Leila!” he said.

She smiled back at him. For her, perfect wouldn’t ever be as good as setting foot on another planet.

“Hello, Dr. Kraft!”

For an overachiever, interviews are like a sport. Derrick Johnson chose a yellow paisley tie with a lemon-yellow shirt. He had practiced his slightly gap-toothed smile. And now Kraft was looking at him through the screen, asking him the first of eight questions each candidate would answer. Four were personality questions, to prove they were dedicated team players. Four were knowledge questions, to prove they were intelligent enough to study the assigned technical materials.

“Tell me about the day when you decided to settle on Mars with no return to Earth, and why?”

That day seemed so long ago. Derrick was 29 now, and had long since quit his government contracting job. He was working for the Young Presidents Organization, a network of young executives and business leaders, achievers like himself.

And now he had Jonathan. They met in November. Derrick loved the way Jonathan’s hair stuck out of his slouchy hats, the way he was always Googling the answers to their silly arguments. He loved the selfie of them together on the home screen of his phone.

Maybe it was Jonathan, or the new job, or just being two years older that made Derrick finally grasp the significance of committing to Mars before he even turned 30. He would never be mayor of D.C. Or own a house with a yard. Or have a wedding. He would never have the two kids he had always envisioned, one genetically his and one his husband’s.

Jonathan didn’t need to know any of this yet. Derrick planned to wait until he found out if he was one of the 100 candidates moving on before he said anything about Mars.

And then, two days before Derrick’s interview with Kraft, they were at Shaw’s Tavern and the bartender was asking, “Hey Derrick, how’s that Mars thing going?”

Finally, they had to talk, and it confirmed his fears: Jonathan had no intention of staying with someone who was going to leave. But they made a pact. There were five weeks until he would learn if he made the cut. Until that day, they wouldn’t bring it up again.

In his space-themed bedroom, Dan excitedly answered every question of the video interview, trying to project the personality traits Mars One is looking for: curiosity, adaptability, resilience.

Tell me about the day when you decided to settle on Mars with no return to Earth, and why?

Tell me a story from your life that shows what unique, valuable qualities you bring to a team. Give me some examples what your family and friends say about you wanting to settle on Mars and never come back.

And then, the knowledge questions.

How much general protection shielding against radiation will the crew receive from the structure of the Mars transit vehicle? How many hours will the reserve of water during normal water usage last? How many square meters of power generating surface area will the first settlement install?

And last, the question he didn’t see coming.

After three years on Mars, given the opportunity that a return flight will be possible, will you take the trip?

Dan paused. If he could go to Mars, and then come back, would he? Would they choose him if he said yes?

His answer was long. He talked about the psychological effects, the readjustment to gravity, the importance of each team member’s skill set.

“I’m going with the idea that I’m going to stay. So, no,” he said, nodding to the screen. “I’m here to stay.”

The interview ended. He got up, shut his computer and walked out of his bedroom, closing the door on the “Star Trek” quote on the wall:

“To boldly go where no man has gone before.”