A couple of leafy, green lettuce plants poke up from the bottom of the coffee-table-size dome. They are just for show, a second sprouting of heads that first grew in this mini-Mars. “Back when we started this, there was no manned mission to Mars at all,” systems engineer Philip Fowler said at the Space Life Sciences Lab. “It didn’t exist. So we had somewhat of a problem in justifying why we were doing this.” He and plant scientist Vadim Rygalov, on loan to KSC from the University of Florida, have worked to discover how plants grow in a low-pressure atmosphere.