When admiral George Anson reached the shore of England in 1744, four years after setting sail, he brought fewer than half the 2,000 men he'd left with. Most of his crew had died of scurvy, and eventually, even the survivors were too weak to throw the bodies overboard. But according to NASA nutritionist Scott Smith, Anson had it easy.

Like other ill-fated expeditions, Anson's was ravaged by a single missing nutrient: vitamin C. Yet he was at least traveling where some food existed. Astronauts on the long-distance voyages of the future will have to bring all their own food, and it will have to contain the right quantities of every vitamin and mineral they need. Scurvy's just the start of what could go wrong. "There's not one nutrient that you could run out of, on a three-year mission, that's not going to end badly," Smith says. Running out of nutrients is only one of the food challenges that Smith and his colleagues at NASA's Johnson Space Center in Houston are facing. If they succeed, they can help humankind make our next giant leap — onto Mars.

"There's not one nutrient that you could run out of, on a three-year mission, that's not going to end badly."

Now Serving

Today, astronauts onboard the International Space Station eat on roughly an eight-day meal rotation. Most of their meals are just-add-water, or come ready to eat in pouches like military MREs: beef tips, ravioli, chicken teriyaki. There are also packaged foods an ordinary person could buy from a store, like almonds or wrapped brownies. Hot and cold beverages come in bags with straws, similar to a Capri Sun. Food packets attach to the galley table with velcro patches so they don't fly away.

The astronauts complain sometimes, Smith says. While the food tastes pretty similar to Earth food, they say it lacks a certain crunch. But for the most part they make do, and even get creative. Expedition 18 flight engineer Sandra Magnus wrote in praise of tortillas, which arrive on resupply trips along with fruit and other coveted fresh foods. "I cannot think of anything that... has not been put on a tortilla," she wrote during her 2008-2009 space station stay. Magnus also developed an elaborate system for food preparation, using recycled plastic bags as mixing bowls and cutting boards, and even managed to cook some onions and garlic by putting them into a plastic bag with olive oil and leaving them in a food warmer for about four hours. And she's not the only astronaut to share her food-prep tips: In 2007, flight engineer Sunita Williams, who served on Expeditions 14, 15, 32 and 33, hacked a tuna noodle casserole by mixing a tuna packet with rehydrated macaroni and cheese.

On the space station, new food arrives from Earth roughly six times a year. But NASA isn't interested in staying in orbit. The next frontier is Mars.

Engineering a menu for Mars

NASA has long planned for human exploration of Mars, with a recent goal of putting people on the planet by the 2030s. A round trip to the red planet would take two and a half or three years. That much food for six astronauts could weigh about 12 tons, according to a 2012 estimate — and that's not counting its packaging. Rather than trying to haul all that on a spaceship, NASA wants to load a vessel with food and send it to Mars before the astronauts set off. That means food scientists have to make meals that will stay good for five years. (Sending astronauts to Mars with a vat of meal-replacement pills would save a lot of space, but even if such a thing existed, Smith says, NASA wouldn't be interested. When astronauts are lonely and far from home, familiar foods help keep them grounded.)

Besides creating a perfectly balanced meal plan with a half-decade shelf life, NASA researchers need to account for disappearing nutrients. Some nutrients break down naturally over time; space radiation — cosmic rays and other forms of radiation that Earth's atmosphere normally blocks — could be an added problem. Meals must take into account the special challenges to astronauts' bodies in space, such as weightlessness, shrinking bones, and squashing eyeballs. And perhaps most importantly, the food has to be appealing enough that astronauts keep swallowing the calories they need to sustain themselves. If they don't eat enough, they won't have the energy or brainpower to face the challenges that arise in space.

How to Eat in a Space Helmet NASA's first concern is that astronauts get enough calories. But it's nearly impossible to eat in a spacesuit, where you can't get your hand to your face. And astronauts on a long-distance space missions might need to make several spacewalks a week — many more than ISS crew members do. On the surface of Mars, they'd also spend a lot of time roaming in their suits. How do you feed someone who's stuck behind a glass helmet for eight to 10 hours? On early Shuttle missions, NASA used to pack a fruit bar inside spacesuits for a snack, but astronauts usually ignored it. And water is the only drink allowed inside a suit these days, ever since an unfortunate moon incident involving a helmet full of Tang. ("It wasn't funny at the time," Smith promises.) Nutritionists wondered about putting some sort of port into the helmet and pushing a straw through. But now NASA is exploring space suits that dock directly to a rover. Astronauts on Mars could bounce over to their vehicle and pop out of their suits for lunch, a setup Smith calls "pretty slick."

NASA is using biochemical research to address address astronauts' other problems. Astronauts Mark and Scott Kelly are NASA's favorite pair of identical twins. Right now, Scott is in the middle of a year-long stay on the space station. While Scott's body adjusts to life without gravity, his twin provides the closest thing to a scientific control — a person with the same genes who's staying on Earth. Researchers are doing very detailed studies of both men during Scott's year in space, looking at their metabolisms, heart health, microbiomes, and mental sharpness. Non-twin astronauts are having their blood and urine scrutinized, too. Researchers want to know exactly what's happening in an astronaut's body, and whether nutritional fixes can address common physical problems.

Researchers want to know whether nutritional fixes can address common physical problems in astronauts.

Astronauts' muscles and bones shrink in space. Exercise seems to be an imperfect solution, at best. But recent research showed that astronauts tend to have too much iron in their bodies, and those with the highest iron levels lose more bone — so a dietary change might help. Astronauts who eat more fish, on the other hand, seem protected from bone loss.

Some astronauts also experience vision changes, including a slight flattening of their eyeballs, after long space missions. This might have to do with how fluids slosh around in microgravity. New research by Smith and others has shown that there's also a nutritional factor. Astronauts who are prone to vision problems have a genetic difference in how their bodies process folate and vitamin B12. This means there might be a nutritional fix to the problem, though it will take more research to find it.

After scientists figure out the correct nutrient balance for astronaut foods, they'll still have to make those nutrients last for five years. Vitamin C, for one, breaks down easily in foods. When NASA researchers left some astronaut food staples (including bread pudding and "carrot coins") in storage for just one year, the foods lost vitamin A and vitamin C, along with folic acid and thiamin. A study of different food-processing techniques found that nothing made sweet and sour pork last for five years — or any other food, for that matter — although freeze-drying had potential.

NASA doesn't want to use pills to replace missing vitamins. Our bodies don't always treat nutrients the same when they come in pill form, for one thing, and astronauts taking supplements might feel less need to eat their actual food. Also, too much of a nutrient can be as much of a problem as too little. The only supplement NASA gives crews is vitamin D, since astronauts don't get enough sunlight to make the vitamin in the usual way.

Astronaut Farmers

Growing crops on the spaceship — and even on the surface of another planet — could solve several of these problems at once. Astronauts wouldn't need to lug as much food with them. They'd have fresh produce rich in vitamins. And they could mix up their menus with some of that texture they miss.

This August, astronauts on the space station tasted the first-ever bites of a crop grown in space. It was red romaine lettuce, sprouted from pillows under purplish lights. (The first harvest had been flown back to Earth to make sure it was safe to eat.) In a video, astronaut Kjell Lindgren uses scissors to snip lettuce leaves while two crewmates bob nearby. After dipping the lettuce in oil and vinegar, the three men "toast" by bumping their leaves together, then take a bite. "That's awesome!" Lindgren says.

NASA's food scientists are researching other crops that could be grown in flight, including dwarf tomatoes and peppers, and even dwarf plums. On Mars, astronauts might grow not just fruits and veggies, but staple crops like wheat. Researchers will look into what crops might make good candidates, and what tools astronauts would need to grow and harvest them on the surface — the planetary version of the lettuce pillow. But turning astronauts into farmers adds new complications. There's the time and equipment needed to process wheat into bread, for example, and the risk of a devastating crop failure.

The biggest issue for food scientists is making sure astronauts eat enough.

Smith says homegrown crops will probably start out as a minor supplement to astronauts' meals, then gradually become a larger percentage of their diet. Self-sustaining Martian farms are in the more distant future.

Looking and smelling ahead

The biggest issue for food scientists, however, is making sure astronauts eat enough. How can the hundredth pouch of sweet and sour pork appeal to a tired, stressed Earthling?

That's why NASA scientists are delving into psychology along with biochemistry. They're studying how the senses of smell and taste change in microgravity and isolation, for example. In one study, researchers are supplying comfort foods and holiday treats to the space station, with astronauts filling out mood questionnaires before and after eating. The crew will also rate solo versus communal meals, as well as the experience of "cooking" the food themselves. NASA believes that on long-term expeditions, good food and pleasant dining will be crucial for keeping morale up. The psychological aspect of those coffee bags and carrot coins is just as important as their vitamin and mineral content. NASA doesn't want its astronauts leaving Earth's neighborhood until it knows both components are there.

"At the end of the day, we're not worried about the muscle cells," Smith says. "We're worried about the human."