(FORTUNE Magazine) – IT'S BEEN ONLY A FEW WEEKS SINCE Paul Allen and Burt Rutan took one giant step for space tourism and won the $10 million Ansari X Prize after sending a manned vehicle called SpaceShipOne into suborbit and back twice. But space buffs are already scoffing that suborbital flights as really just a "sideshow to the large-scale exploration of space," as John Logsdon of the Space Policy Institute puts it. "It's bungee jumping for rich people." Now that tourism has been conquered (at least sort of), industry types are looking ahead to the next space race: colonization. And the biggest name in that field? Jeff Bezos.

In 2002 the Amazon.com founder started a company called Blue Origin, based in a warehouse in Seattle not far from Amazon's headquarters, that is "developing vehicles and technologies that, over time, will help enable an enduring human presence in space," according to the company website. Bezos isn't talking, but the hiring bar, needless to say, is "unabashedly extreme."

Space businesses on the side are of course the new hobby of the rich--even Sir Richard Branson is getting in the mix. But if the words "enduring human presence in space" are any indication, Bezos is up to something much larger than suborbital stunts. (Though he's interested in that too: To colonize space, you have to get there first. His first order of business, again according to the website, is to build "a crewed, suborbital launch system that emphasizes safety and low cost of operations.") For Bezos, dreams of human life on other planets are hardly out of character. He gave his valedictorian address at Palmetto High School in Miami on the need to colonize space in order to secure humanity's future, and he once won a trip to NASA for a paper on "The Effect of Zero Gravity on the Aging Rate of the Common Housefly."

"Space was his passion," says one high school friend who remembers Bezos's collection of shuttle posters and his dog Kamala, named after a Star Trek character. "Passions don't change. Amazon was a means for making money, but I don't think it's ultimately satisfying enough for him. He definitely felt that the future of humanity was beyond Earth."

Because of the secrecy surrounding the company, and Bezos's obvious passion for space, the industry is alive with rumors: "Space is, like, Jeff's No. 1 interest," one space gadfly told FORTUNE rather conspiratorially. "I heard he's putting a billion dollars into the company. "

Interestingly, Bezos isn't the only techie with such Robert Heinlein--inspired dreams. Elon Musk, who sold PayPal to eBay for $1.5 billion, also has long-term hopes regarding the colonization of outer space. A member of the Planetary Society and the Mars Society, Musk has spent $100 million on his own company, Space Exploration Technologies, of El Segundo, Calif., where he is developing an orbital launch rocket. (He already has a launch deposit from hotel magnate Robert Bigelow, who is working on his own grand dream: hotels in space.) But Musk's true long-term goal, like Bezos's, is colonization by any means possible. "It's one of the greatest things humanity could possibly do," he says. "On a species level, it would be huge."

There are hurdles, of course. A one-way flight to Mars takes seven months, and the interplanetary geometry required to make a landing comes around only every year and a half. In addition, "Mars has a poisonous atmosphere and a toxic surface," says Dr. Louis Friedman of the Planetary Society, "and if you stuck a life form on it, it would be fried instantly." On the other hand, he sees hope: a robotic infrastructure, fueled by nuclear power and populated by humans who live largely indoors ("like they do in Minnesota"). Residents would grow their own food in greenhouses and could only venture outside in skintight spacesuits. Friedman estimates that it would take around $50 billion to fund a full-scale Mars colonization project, and he thinks such a plan is a long way off." If Bezos wants to see colonization happen," Friedman says, "a concurrent problem he will have to solve is eternal life." -- Grainger David