So forget about fictional little green Martians invading Earth. In the not-too-distant future, you could be packing for a trip to our solar system next-door neighbor — a voyage that, with current technology, would take about eight months each way.

Think of the frequent-flier miles! At its closest, in August 2003, Mars was “just” 34.8 million miles from Earth. On average, though, it’s about 140 million miles away. The distance varies because both planets are constantly moving.

After traveling all that way, you’re probably going to want to stay awhile. NASA is working on two plans. One would have you and your fellow astronauts remain on Mars for a few weeks. The other plan has you staying for more than a year.

In either case, where will you live in that desertlike environment? And what will you eat? In addition to the planet’s thin atmosphere, its rocky, sandy surface lacks liquid water and endures weeks-long dust storms, so growing food outdoors is a dream decades away at best.

These are among the millions of questions that scientists and engineers are tackling. And they’re seeking ideas from all of us.

Picking our brains

The 3-D-printed Habitat Challenge is a five-year competition hosted by NASA and its partners to design housing for deep-space exploration, including trips to Mars.

Basically, the pros want to see what the rest of us can come up with to build reusable shelters using recyclables and materials found on site.

The competition, with $3.15 million in prize money, is in its third and final phase and will end in the spring.

“It’s been eye-opening to learn from people outside NASA their concept of what a house on Mars would look like,” said Monsi Roman, program manager for this and similar NASA competitions at the Marshall Space Flight Center in Alabama. “It’s amazing what people can come up with when they’re not constrained by money, time and other limits.”

NASA’s goal, she said, is to have its experts look at an entry and think: “Yeah, that makes 100 percent sense. How can we not have thought about that before?”

Robots will go first

For the competition’s final phase, entrants are building virtual or reduced-scale models of their habitats. Each must be able to house four astronauts for one year and include space for cooking, sleeping and recreation in addition to a work area. Some plans include an indoor garden. All must offer protection from harmful radiation levels much higher than on Earth.

The heart of the challenge is that the habitat must be ready for use before any astronauts arrive on Mars. Robots will go first and collect local materials to create a mixture called Martian concrete. One or more 3-D printers sent with the robots will use that concrete and other materials to build the habitat.

Entries have come in various shapes and sizes. Team Zopherus from Arkansas won the first stage with a habitat that looks like the head of a Minion covered in brown rocks (without the goggles). A multi-legged landing vehicle moves like a giant spider and sends out buglike rover robots to collect stuff.

Mississippi’s Kahn-Yates team took third place with a sleek, shell-like design intended to lessen the effects of dust storms and let in more sunlight on a planet where the average temperature is minus-81 degrees!

AI SpaceFactory of New York came in second with a candy-barrel design that builds up, not out, which the team says will make 3-D-printing easier. It’s plain on the outside, and its futuristic interior has a bright “skyroom” on the top level. It’s so awesome that one Earthling who viewed it online said, “We need that . . . here.”

See for yourself