Fast forward to the year 2015, nearly 500 years after Magellan set sail. A group of six space explorers sets off toward Mars in the best rocket ship ever built. Many scientists in the space community believe this scenario will come true.

Such a journey would be similar in many ways to Magellan's voyage: It would take about three years—the same amount of time it took Magellan's ships to circle the globe. The same problems Magellan faced—mutiny, health, and navigation—plus a host of other issues will also have to be solved before anyone travels to Mars and back.

When humans take the leap to explore another planet, the crew will have been thoroughly tested for their ability to get along and for health risks that could sabotage the journey. They will also be trained to fly a ship so far from Earth that communication back and forth could take up to 40 minutes.

Life on Board

The space-faring crew will live, eat, and sleep in a compact spaceship no larger than a few hotel rooms. Strict protocols and guidelines for handling any crisis that may arise will be developed and rehearsed. Much of the simulation will take place on the International Space Station.

Magellan and his crew had to battle their way around the tip of South America and into the Pacific Ocean. It took them 42 days of arduous sailing to break away from the currents of the Atlantic. By the time he reached the Pacific, Magellan had lost two ships—one to storms, the other to mutineers.

Astronauts traveling to Mars would have something far more dangerous to face—galactic and solar radiation that can rip human DNA to shreds, causing cellular mutations and possibly cancer.

The spaceship would have to be built to shield the occupants from these invisible bullets. The craft and crew, while cruising between the planets, would also be doing so with little protection from a gigantic solar storm called a coronal mass ejection.

Another health issue is the severe drop in bone mass due to weightlessness in space. Our bodies are built and operate best when living on Earth. In micro-gravity muscles atrophy, and through a complex and not quite understood process our bones stop regenerating.

The space community will need to develop systems to produce food, purify their water supply, regenerate oxygen, and remove undesirable components of the air. This would have to be a tightly controlled and closed-loop system in which the growth of edible plants would provide food and contribute to water purification, air revitalization, and the processing of waste materials.

The entire system would have to take up as little room as possible, use a small amount of energy, and not take up too much of the explorers' time.

Though Magellan used the best maps available in 1519, he still miscalculated the size of the Pacific Ocean and had to sail for more than three months without sight of land.

The fastest and most sensible route to Mars is on a path that only occurs every 22 months when Earth and Mars are in a certain alignment with each other. The journey would still take at least three months each way. Once the explorers reached Mars they would have to stay there for 550 days until the planets realigned themselves.

All of these challenges to sustaining humans in space—mental, physical, and technological—can be solved. Each step along the way will advance our knowledge of science, technology, and medicine.