SpaceX aims to help establish a million-person city on Mars. What would all of those people eat?

What might it take to feed a million people on Mars? Lab-grown meat, tunnel-grown crops and cricket farms, a new study finds.

When it comes to plans for crewed missions to Mars , NASA typically assumes round trips with only brief stopovers on the Red Planet. However, commercial space companies have emerged with the goal of colonizing outer space, with SpaceX specifically aiming to develop a civilization on Mars .

The most practical strategy for long stays on Mars involves living off resources that already exist on the Red Planet instead of relying on resupply ships from Earth. The five major consumable resources that researchers identified Martian settlements would need include energy, water, oxygen, construction material and food, and the first four are potentially abundant on Mars.

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For instance, solar power, likely supplemented with nuclear-fission reactors , can help provide energy for would-be Martians. Ice and hydrated minerals on Mars are sources of water. Carbon dioxide can get converted into oxygen. Finally, Martian soil can be readily made into bricks for building supplies.

In comparison, there is no food naturally available on Mars, and there is no easy way to create it from any raw materials on the Red Planet using, say, a simple chemical reactor, the researchers said.

"Food is probably going to be the hardest thing to make locally on Mars, and you can't just import it all if you want to have a self-sufficient settlement," study lead author Kevin Cannon, a planetary scientist at the University of Central Florida in Orlando, told Space.com.

Given this challenge, the scientists wanted to see what it might take to reach the radical goal of producing enough food on Mars to feed 1 million people.

"We were working with a lot of people who wanted to grow plants in the simulated Mars soils we create, and this led us to look at what research was being done in terms of producing food for future human missions to the moon or Mars," Cannon said. "It turns out most of the focus has been on very low-calorie vegetables, and the latest innovations in alternative protein sources were not being considered. We asked the question: Instead of a short NASA-style mission to Mars, what would it take to feed a city of 1 million people, like what SpaceX is imagining?"

The researchers noted that raising farm animals for dairy and meat would not be practical on Mars in the near term because of the challenges of shipping them across space. At the same time, they noted that most people do not want to go completely vegetarian. The solution? Insect farms and lab-grown meat, they suggested.

Insect farms are well-suited for Martian cuisine , as they provide a lot of calories per unit land while using relatively minor amounts of water and feed, the researchers said. Crickets in particular are one of the more promising examples of edible insects, with cricket flour potentially incorporated and hidden in many different recipes, they noted.

"Bugs are the way to go, if people can get over the gross factor," Cannon said.

For those who do not fancy insects, "cellular agriculture" — that is, food derived from cells grown in lab dishes — could help people on Mars eat a somewhat more familiar diet, the researchers said. Everything from algae to meat and fish to cow-less milk and chicken-less eggs are now possible, they said. The large amounts of money that investors have poured into refining such technology has already driven down the costs of a cultured meat burger from $325,000 to $11 per patty in two years, they added.

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When it comes to crops, concept art of Martian settlements usually features greenhouses, but those may not prove practical, the researchers said. Because Mars is so far from the sun, even on the' equator, where sunlight is strongest, the amount of light plants would receive would be similar to what they get in Alaska. Moreover, although greenhouses are made of clear window panes, these still typically absorb 50 to 70 percent of light on Earth, and may block even more on Mars, since a stronger material is likely needed to support a heated, pressurized interior, given how the air on the Red Planet is much colder and thinner than on Earth.

Instead, tunnels lit with high-strength LEDs are likely needed to grow plants on Mars, supplemented with sunlight collected and piped down through fiber-optic cables, the researchers said. Soilless farming involving hydroponic or aeroponic systems is possible, but those strategies would require more mass shipped to Mars in the form of trays, pumps and reservoirs, they said. In addition, soil-based farming may be more robust against plant disease, but inorganic Martian dirt would require significant research and treatment to convert it to a living soil that could support plant growth, the researchers added.

Previous research suggested a number of crops may prove especially practical when it comes to feeding Martian colonists, such as wheat, corn, soybeans, peanuts and sweet potatoes. Genetic modification could also make plants more useful in a variety of ways for Martians — for example, by consuming more carbon dioxide and boosting productivity.

"Almost all research to date has focused on growing plants to feed astronauts, but plants take up a ton of space, and on another planet, that means building large indoor factories that need to be pressurized, heated and lighted," Cannon said. "If you want to feed a large population on another planet, you have to move away from the idea of watery vegetables and really think about the tremendous amounts of energy, water and raw materials needed to produce enough calories."

To see what it might take to feed a Martian city of 1 million people , the researchers modeled a population that grew from immigration as well as through a birth rate of 10 per 1,000 people per Earth year, a rate typical of developed nations on Earth. All in all, they assumed about 6,900 crewed ships were needed to deliver about 1 million immigrants to Mars over the course of a century, with about 340,000 people born on Mars during that time.

The scientists calculated the number of calories each person would need, and modeled land use given a diet that included wheat, corn, sweet potatoes, crickets and lab-grown chicken. They found that a Martian colony of 1 million people could achieve self-sufficiency in terms of food within 100 years, relying on about 9,000 miles (14,500 kilometers) worth of tunnels about 12 feet (3.6 meters) wide, which could be stacked vertically.

Related: Space Food Photos: What Astronauts Eat in Orbit

However, these colonists would need massive amounts of food imported in the interim, carried on nearly 54,000 cargo shipments. The scientists noted there were a variety of strategies that could be used to significantly reduce the amount of imported food, such as increasing the rate of farm construction on Mars.

Future research on how to best feed Martians should focus on boosting crop productivity, working out the most efficient and palatable insect species, improving the flavor and texture of cultured meat, improving the efficiency of the LED lighting used to grow crops, and developing automated methods for rapidly building pressurized, shielded areas to house farms, the researchers said.

"The obvious criticism is that this is science fiction — human missions to Mars are decades away, so why bother working on this topic now?" Cannon said. "Anyone who thinks along these lines needs to take a serious look at what SpaceX is doing — they are already building and testing prototypes of the ships that will send the first settlers to Mars."

It's time to "work out how to make it happen," he added.

The researchers said research on how to feed Martians could also help feed people on Earth.

"The constraints imposed by Mars — a cold, thin atmosphere — force you to produce food in ways that are actually more sustainable and ethical than what's done on Earth with current factory-farming practices," Cannon said. "So, switching to a 'Martian diet' can help our planet." The scientists created a website, http://eatlikeamartian.org , which gives some information on how to do just that.

Cannon and study senior author Daniel Britt at the University of Central Florida detailed their findings online Aug. 30 in the journal New Space.

Editor's note: The original version of this story mistakenly referred to Kevin Cannon as Keith Cannon.