There's no pizza on Mars, but scientists have found a solution to this problem for hungry astronauts: a pizza printer! NASA, the American space agency, has developed a machine that "prints" food. They showed a model of the printer in Austin, Texas last month. How does it work? Cartridges  filled with powdered dough , cheese, sauce, water and oil put the ingredients layer by layer onto a printer bed. The printer bed, which gets hot from below, cooks the food as it's being printed. Since most of the ingredients are powdered, they can be sent into space and stored for many years without going bad. Water makes food go sour, so the food powders are mixed with water and oil only when they are being printed. "Long-distance space travel requires more than 15 years of shelf life for food." says Anjan Contractor, whose company developing the printer. " We take water out, and in that form, food will last maybe 30 years." In outer space, there are far fewer choices for astronauts for dinner. Most of their foods--even things like beef or shrimp--are eaten from bags as powders . Scientists hope the new food printer can be used to make more delicious food in outer space, keeping astronauts healthier and happier. But the printer is not limited to use in outer space. Scientists think it could be useful on Earth, too. It could allow personal meals to be made at the dinner table, according to each person's different needs. "Let's say someone is an athlete in the family, and he needs more protein ," says Anjan Contractor, founder of Systems and Materials Research Corp, the company developing the printer. "We can design recipes for him and print out more protein-nutritious food for him." In outer space, food can be stored for many years without going bad  _  .
when it's mixed with water when it's mixed with oil when it's powdered when it's put in the fridge