President George H.W. Bush estimated that it would cost more than $500 billion, and in 2010, President Obama and his administration called the potential mission "far-reaching exploration milestones."

A manned journey to Mars has fascinated science fiction authors and scientists for more than a century, according to The Week, but is it a feasible goal?

NASA still does not have a budget for the potential mission, nor the technology to safely land humans and bring them back to Earth.

"The challenge ahead is epic, but historic," Former astronaut Buzz Aldrin told The Week. "We are on a pathway to homestead the Red Planet."

Getting humans to Mars would prove difficult for a number of reasons. For starters, Earth and Mars are 34 million miles apart at the closest points of their orbits, and astro-engineers predict it would take a manned spacecraft about 10 months to reach the Red Planet, requiring tons of food, equipment and fuel for the grueling space journey.

Even if supplies are sent in a separate vehicle, there is also the issue of landing safely, as Mars' atmospheric pressure is less than 1 percent of Earth's, which would make it very difficult for a spacecraft flying towards the surface at about 13,000 miles per hour to land without incident.

"We're talking about landing perhaps a two-story house, and then another two-story house with fuel and supplies right next to it," former NASA technologist Bobby Braun said to The Week. "That's a fantastic challenge."

Scientists are also concerned about the potential health risks associated with living on the Red Planet. Long-term exposure to reduced gravity, radiation, pro-longed days and extraterrestrial atmospheric conditions may lead to bone degradation, muscle loss, and swollen optic nerves from too much time in zero gravity.

In a Russian experiment known as Mars 500, six men were confined for 500 days under conditions meant to simulate a Mars mission, and researchers discovered that these men and potential Mars travelers may face severe sleep disturbances, lethargy, and depression.

Mars' ultra-fine surface dust also concerns scientists who worry that the highly chlorinated salts may lead to respiratory problems and thyroid damage.

Mars explorers would have to construct pressurized, air-tight quarters with plenty of supplies for long-terrm living, with long-term food supplies of course. Explorers would dine on powder foods and concentrates that would mimmick the texture, taste and smell of natural Earth food.

"I've had a deep need to explore the universe since I was a kid," Peter Greaves, a self-employed technologist, told The Week. "I envision life on Mars to be stunning, frightening, lonely, quite cramped, and busy. But my experience would be so [different] from all 6 to 7 billion human beings. That, by itself, would make up for the factors I left behind."

John Grunsfeld, among the researchers, astronauts, and space exploration firms who see establishing a Mars colony as crucial to the survival of mankind.
Stephen Hawking agrees, explaining that the "human race shouldn't have all its eggs in one basket, or on one planet."

Shrinking resources, possible nuclear destruction, climate change, overpopulation and a possibility of hostile aliens may make Mars essential to keep humanity going.

"I believe that we will eventually establish self-sustaining colonies on Mars and other bodies in the solar system," Hawking said. But he estimates it won't happen "within the next 100 years."