NASA’s first observations of Titan date back to the Voyager missions that toured the outer planets and moons in the 1970s and ’80s. The spacecraft’s cameras couldn’t penetrate Titan’s atmosphere, the thickest in the solar system. The moon looked like a marble the color of mustard, so smooth and featureless that it felt almost defiant, guarded against these flying objects from another land.
A European spacecraft arrived on Titan in 2005. From beneath the haze, the Huygens probe captured photographs and beamed them back to Earth. The views felt at once alien and familiar. “Suddenly we get a picture of gullies, which we didn’t know existed,” Jonathan Lunine, who has studied Titan since the early 1980s, once told me about the moment the images arrived. “I screamed when I saw those.” On Earth, flowing water carves gullies into rocky landscapes. On Titan, methane is responsible.
The tour didn’t last. Huygens exhausted its batteries in less than three hours. But astronomers still had eyes on Titan. Huygens was dropped off by Cassini, a NASA spacecraft that remained in orbit around Saturn until 2017, occasionally swinging by the moon to collect data and pictures.
Cassini provided evidence for the methane lakes there. Scientists had long predicted their existence, but they were full of surprises. Titanian lakes are calm and textureless, with only a few ripples here and there. The kind of waves rolling across Lake Michigan are nowhere to be found, and scientists are still trying to figure out why.
When Cassini ran out of fuel, NASA faced an uncomfortable scenario. A dead spacecraft is impossible to control, and scientists worried that Cassini would tumble into Titan and scatter itself across the surface, possibly contaminating life—if any existed. To protect the hazy moon, engineers deliberately shoved Cassini into Saturn, a gaseous planet incapable of hosting life.
Dragonfly will search for signs of life, ancient and present. In Titan’s atmosphere, spacecraft have detected carbon, hydrogen, nitrogen, ethane, and other elements on which life on Earth depends. They’ve even found a compound that could interact with the methane and ethane to create cell-like membranes. Scientists suspect that Titan might even have water—real, actual H2O—lurking beneath its surface.
“These ingredients that we know are necessary for the development of life as we know it are sitting on the surface of Titan,” says Zibi Turtle, the principal investigator for the mission and a planetary scientist at Johns Hopkins University’s Applied Physics Laboratory. “They’ve been doing chemistry experiments, basically, for hundreds of millions of years, and Dragonfly is designed to go pick up the results of those experiments and study them.”
After decades of orbiters, rovers, and landers, the thought of a little drone buzzing around an alien world is refreshing, almost unimaginable. According to the Dragonfly team, the spacecraft could cover tens of miles in an hour. Thanks to Titan’s fleecy atmosphere and low gravity, bouncing around is quite easy. (If astronauts joined Dragonfly, they could don winged suits and flap around the terrain, coasting alongside the robot.)