Future humans could live in subway-like tunnels on Mars

Spacesuits that can deal with Mars' extremely low and unpredictable pressure will be essential.

Mars exerts only 0.06% of Earth's surface pressure. Depending on the location, Earth's air pressure can vary about 10%, whereas Mars' can vary as much as 50%.

This month, NASA unveiled a spacesuit prototype that can take the pressure. With the Z-2 suit, astronauts can maneuver in and out of rovers, collect samples, and walk around with ease.

Once we have the suits, we will also need to shield the colonies from cosmic rays.

NASA recently reported that solar wind stripped Mars' atmosphere and turned the planet into a wasteland. Now, it has about 1% of the atmosphere of Earth.

Zubrin says that our best bet is to cover the colonies in sand bags.

Good news: we have pretty much everything we need to physically build space colonies.

Zubrin says we could live in inflatable, aluminum habitats connected by underground tunnels. This would make it easier to travel between the habitats without a spacesuit.

Since Mars sees plenty of sun, plants can grow in greenhouses. Most plants are also very resistant to radiation, Zubrin says.

Organizations, like Zubrin's Mars Society in Utah and HI-SEAS in Hawaii, simulate Mars missions in fake colonies. At HI-SEAS' research station, cots in the 1,300-square-foot domes include the bare minimum: a foam mattress, a narrow table, and a set of drawers.

When we run out of food or a part of the habitat breaks, we will need to figure out how to transport extra supplies.

Until the colony can sustain itself, we'll have to drop off cargo from Earth. To minimize trip time, astronauts should travel when Earth and Mars align, which happens every 26 months, Waldman says.

"If it does happen, it will take more collaboration than we've ever seen before," she says. "It'll be more worthy of celebration than the moon landing, because it will take a lot of people coming together on an unprecedented scale."

"The key ingredient is courage," says Zubrin. "That's what got us to the moon."

That, and billions of dollars of funding over decades.