A vital but unasked question is: what happens to human waste in space? Right now, astronauts bring it back home with them, but on longer space voyages, other solutions will be needed.
This will become more important in the future, when long space voyages are planned. Karen Miller writes that on a two-year trip to Mars, a crew of six humans will generate more than six tons of solid organic waste. Before we can venture out on long space trips, we’ll have to figure out how to recycle it.