Dining on alien planets might be a way off, but at least when we do there will be salad -- because we've already developed the means to grow lettuce on other worlds.
This image shows the set-up used by researchers at the German Aerospace Center, who have been pioneering the techniques required to grow "space lettuce". Bathed in red LED light -- to make up for a lack of sunlight -- these leaves grow in an aeroponic greenhouse module that should in theory work on the moon or Mars.
There's no soil used here. Instead, the plant are suspended, their roots dangling free to be sprayed with nutrients for 20 seconds every two minutes. Where do those nutrients come from? Glad you asked: In fact, these stellar greenhouses will extract chemicals from astronaut urine to create fertiliser. Yum. [New Scientist]