A one-way ticket to Mars: would you join a mission to Mars if you could never return to Earth?

• Author: Potenza, Alessandra
• Position: SCIENCE

How would you like to be the first person to set foot on Mars? There's only one catch: You can never come back.

A Dutch nonprofit called Mars One plans to send people to colonize the Red Planet by 2027. But to make the mission affordable, its founders say there can be no returning to Earth. That doesn't seem to have deterred many would-be explorers: More than 200,000 people from all over the world signed up.

Mars One has already narrowed the list of applicants to 100 finalists, with 24 to be selected for the mission in the fall. They'll face years of training before boarding a 6- to 7-month spaceflight to Mars--if the project ever gets off the ground (see Colonizing Mars).

Why are so many people willing to travel 140 million miles to live--and die--on another planet? Maybe it's not as crazy as it sounds. Humans have been exploring the unknown forever--often at great risk. When Christopher Columbus set sail to find a western route to Asia in 1492, he had little idea of what loomed beyond the horizon. And when 102 pilgrims left England and landed at Plymouth Rock in Massachusetts in 1620, they couldn't have known what life would be like in the New World. More than half died of starvation and disease within the first few months.

"Just like the American pioneers settled the West," says NASA engineer Jason Crusan, "today's students will have the opportunity to be the first humans to visit the Red Planet and pioneer Mars."

Laurel Kaye, a 21-year-old senior at Duke University in North Carolina whose first word as a baby was moon, agrees. She's one of the Mars One finalists and sees herself as a 21st-century pioneer: Going to Mars for her is a bit like what her ancestors experienced when they came to America from Europe in the 1800s.

"They saw a different future out there for them, and that's what I see," she says. "This is humankind's next step in that direction."

Scientists agree that of all the places in the solar system that earthlings might colonize, Mars is the most promising. Like Earth, Mars has seasons, its days last roughly 24 hours, and its gravity is 40 percent that of Earth--enough to avoid the severe bone and muscle loss caused by lack of gravity. Yet Mars remains a brutal place for humans. Its average temperature is -60 degrees Fahrenheit, it has no liquid water, and its atmosphere--made largely of carbon dioxide--is unbreathable. If you went for a stroll on Mars without a spacesuit, you'd die within minutes.

"No more smell of fresh...