Maxwell, on the other hand, had long assumed that a career in space was out of reach.

He was raised in an economically depressed rural area of eastern North Carolina, although his accent could just as well place him from the Midwest. His parents divorced when he was 7; after his mother moved to Florida, he spent time bouncing between the two states until college.

His father was a railroad engineer for most of his career, although he previously worked as a dean at various colleges.

Carl Sagan was Maxwell's childhood hero. He adored watching the 13-part TV series Sagan hosted called "Cosmos: A Personal Voyage," first broadcast in 1980 on PBS.

In one episode, the scientist talked about what it would be like to go to Mars. Only last year, Maxwell watched the episode again and remembered it mentioned a prototype Mars rover, which at that time seemed a futuristic idea.

"I realized in that moment that that's where I get this sense that I've grown up and stepped into this fantasy world that I had when I was a kid, because I have," he says with excited emphasis.

As a child, Maxwell loved imagining what it would be like to go to other planets. But as an older teen, he assumed he would study hard and end up in a career that seemed more common and attainable than space exploration, such as banking.

"This kind of thing always seemed to me like the kind of thing other people do," he said. "There's me. And there's this big invisible glass wall. And there are people who are doing stuff like that."

Maxwell believed he could never cross over to the other side of glass wall.

It wasn't until he got hired by NASA, after completing his master's degree in computer science, that he realized the wall never existed.

Maxwell is living his fantasy now, but he hasn't always had such luck. At age 20, while double-majoring in English and computer science at East Carolina University, he learned that his swollen lymph nodes were a symptom of stage 2 Hodgkin's lymphoma. The cancer had spread in his neck and chest. He went through nine weeks of radiation treatments and has been cancer-free ever since.

Just days after the treatments ended, he left for graduate school at the University of Illinois at Urbana-Champaign. Going from a state school to a prestigious engineering institution, he was floored on the first day when a professor expected everyone to have already learned the material in the first six chapters of an algorithms textbook. Maxwell had to quickly catch up on his own but says he loved learning so much at once.

And though he feared he couldn't afford his master's degree, he found work with the research and development arm of the U.S. Army and left school debt-free.

He had intended to go to Illinois to work toward a Ph.D., but ultimately the cancer changed his priorities.

"I was interested in going out and making tools for people to use," he says.

JPL came to recruit at his school in fall 1993, and he remembers telling the recruiter how he was fascinated by NASA's Voyager mission -- twin spacecraft that had photographed Jupiter in unprecedented detail. His excitement apparently made an impression: He landed an interview at JPL in January 1994, and started his job that June.

Today, he lives on a quiet Pasadena street, in a cozy house that boasts some of his nerdy treasures, including an extensive collection of science fiction books. "But then my life became science fiction," he said, explaining why he's reading more Shakespeare and Dickens these days. As he shows off his collection, his cat Molly purrs, demanding his attention. The brown and black marbling on her otherwise white fur looks somewhat like the Martian landscape, although that's not why he adopted her.

A glass-paneled cabinet hosts metallic "Star Wars" and Mars rover lunch boxes. There's a vial of a substance he calls KimSim, a material his girlfriend helped create to figure out how to rescue the Spirit rover after it got stuck in a "sand trap" of alien soil on Mars in 2009.

And there are stones from the Cotswolds, an area in England he bubbles with excitement over. He says, "Wait, wait," like a child about to demonstrate a new toy, and runs to get a book filled with images of the region. He likes the views from the ground better than the aerial shots -- ground-level is more like what a rover would see, he explains.

The wider, well-manicured street perpendicular to his own, with larger houses and roses growing on front lawns, is the sort of place where he'd always wanted to live, but he says the houses are "wicked, ridiculous, crazy expensive." Still, he loves the house he bought, with the added bonus of a lemon tree growing at its side.

It's a bit like how he loves his job driving a vehicle on Mars, even though he dreamed of becoming an astronaut.

"Things in my life aren't quite how I pictured them," he said, "but they rhyme."

At NASA, not just a sojourner

It's been 18 years, but Maxwell still occasionally interrupts himself to say things like "I can't get over that I work at a place called the Spacecraft Assembly Facility" when he mentions that building at JPL.

For the first couple of months there, Maxwell felt like he was in a foreign country where he didn't speak the language. He says it was fun to be clueless about the acronyms his colleagues were throwing around. "Now, I'll use 10 acronyms in a sentence and won't think twice about it," he says, "but you kind of have to pick up the culture."