Aircraft weighing as little as a chocolate bar could one day be darting over the surface of Mars with the agility of dragonflies and the eyes of bees. Australia-based scientists say they have developed navigational and flight control devices based on research into several types of insects. The resulting sensors are so small they can be placed on “microflyers” weighing just 75 grams. The team of researchers at the Australian National University won over Nasa during a test flight of a prototype last week and the US space agency has agreed to help finance further work.