In April 2013, on board the unmanned spacecraft BION-M, a thick-toed gecko wriggled out of its polyurethane collar. In microgravity, the object floated away, then floated back toward the animal, then away again, approaching another gecko, and then a third. The animals got curious. One pushed the collar with its snout. Another tried inserting its head into it. Yet another pinned the thing down to the floor. As the spacecraft orbited Earth, the geckos started to play. Russian scientists described …