NASA has chosen its next planetary mission, which will send a flying rover called Dragonfly to Saturn's largest moon, Titan. The size of the Curiosity Mars rover, the unmanned, nuclear-powered explorer will not have wheels, but will fly through the Titanian atmosphere using eight rotors as it looks for organic molecules, including the building blocks for past or present life.

      Sending a robotic rotorcraft 842 million miles (1.4 billion km) from Earth and expecting it to whiz about on a moon with a methane atmosphere – where the -290° F (-179° C) temperature turns water into ice as hard as granite – may seem a trifle ambitious, but it does make engineering sense.

Unlike the Moon and Mars, where previous rovers were sent, Titan has 0.133 Earth gravity combined with an atmosphere that is four times as dense as our planet's. This means that flight on Titan is actually easier than on Earth – which is fortunate because the surface is a mixture of lakes, sea, and streams made of liquid hydrocarbons, and sand dunes made of organic "snow." That makes wheeled or tracked rovers impractical for the foreseeable future, but a rotorcraft that can hop from place to place is another matter.

     Since Dragonfly isn't scheduled to launch until 2026 and arrive at Titan in 2034, it's still in the design phase, but the basic blueprint is for a Curiosity-sized rover set on a pair of landing skids and equipped with eight one-meter (3.3-ft) rotors powered by batteries charged by a radio-thermal generator (RTG) nuclear power plant. It will be able to fly at 22 mph (36 km/h) at an altitude of up to 13,000 ft (4,000 m), in a series of flights that will be as long as five miles (eight km).