(CNN) -- When Neil Armstrong took one small step onto the moon in 1969, it seemed only a matter of time before the advent of thriving space colonies and summer vacations on distant planets. But after an initial flurry of moon landings, manned lunar expeditions dwindled: the last time an astronaut left his footprints on the moon was in 1972.



Plants such as lettuce, peppers and tomatoes will be on the menu at Moon Base One.



Then, in January 2004, President Bush announced NASA's intention to return humans to the moon by 2020, and in 2006, NASA announced plans to set up a manned lunar outpost by 2024, with the European and Russian Space Agencies now planning bases of their own. After years in limbo, the dream of living in space is alive once more.



Sustaining long-term space habitation presents space agencies with a whole new set of technological and logistical challenges. Currently, the International Space Station supports three astronauts in a low Earth orbit, with food supplied periodically by space shuttle. But, just as home cooking is cheaper than getting takeout, when it comes to more permanent settlements, this kind of supply voyages would be prohibitively expensive: we will need to grow our own food in space.



Raymond Wheeler, a plant physiologist at Kennedy Space Center, explained to CNN, "In the near term it's not needed, for example on the space station and initial short sorties to the moon, but as you go further and stay longer, regenerative systems become much more cost effective."



Wheeler sees this development of space farming as a gradual process in which space outposts become increasingly self-sufficient. "It would probably be evolutionary," he said. "The first human missions to Mars might set out with everything stowed, but they might set up the beginnings of an in-situ production system -- maybe a plant chamber -- that you could use to grow perishable foods. You wouldn't be providing everything, but in subsequent missions if you returned there you could expand the infrastructure."



Of course, this means growing plants in conditions very different from those on Earth. Yet research has shown that plants are surprisingly adaptable. For example, while plants normally use gravity to direct the growth of their stems and roots, in low gravity conditions they can use light to orient themselves. And research suggests that plants can grow well even at very low atmospheric pressures. That reduces the leakage of oxygen and carbon dioxide from their growth chamber out into space, but crucially, it also reduces the structural requirements of a "space greenhouse," meaning less construction material needs to be shipped into orbit.



Nor is the absence of soil a problem. Many supermarket vegetables are already grown hydroponically in nutrient-enriched water, and research indicates this technique could work well in space. Some have even suggested the loose rock regolith on the surface of the moon or Mars as a growing medium, although additional minerals would need to be brought from Earth.



So what's on the menu at Moon Base One? Well, initial crops would need to be small in stature and grow well in controlled environments with artificial light. Plants such as peppers and tomatoes are already extensively grown hydroponically, while lettuce, with its short lifecycle, would yield fast returns for pioneering space colonists.



But again, Wheeler sees the choice of crops as part of an evolutionary process. He tells CNN, "The first things you might grow would be perishable foods -- maybe vegetables or fruits -- things that don't keep very well if you're on a journey to Mars. Even though you're not providing a lot of calories, these things could have a strong impact in terms of adding color, flavor and texture to the diet."



"The other reason for considering freshly consumed foods on early missions is that they don't require any processing," he continued. "If you were to grow grains, like wheat, you'd have to thresh the seed out of the head, then clean it and mill it to make flour. Staple crops like wheat, soy bean, rice and potato -- things that would
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