Why Mars astronauts need more than just space greenhouses

Thinking about food systems in deep space likely brings to mind something like The Martian where an astronaut is scratching barely enough food to survive out of potatoes grown in Martian regolith. Or perhaps a fancy hydroponic system on an interplanetary transport ship, with artificial lighting and all the associated technological wizardry. But a new paper published in Acta Astronautica by Tor Blomqvist and Ralph Fritsche points out that growing food is only one small part of the whole cycle of providing sustenance for astronauts in space. To really get a sense of how difficult it will be, we have to look at the whole picture.