Journey to Titan

Inside NASA’s Dragonfly mission to Saturn’s largest moon

- BY PHIL PLAIT

IN 2034 NASA SCIENTISTS will be flying around Titan.

Remotely, of course—Titan, Saturn’s largest moon, is more than a billion kilometers away from Earth, a journey no human can yet make. It’s also deathly cold, being so far from the sun. But our robotic proxies can endure the chill and make the trip, and, as it happens, we humans are getting pretty good at making these machines.

Still, even compared with the astounding missions that we’ve already launched to explore other worlds, this one, called Dragonfly, is massively ambitious. The spacecraft is not a lander or a rover; it’s a helicopter, or more accurately an octocopter, with four pairs of spinning blades to take it aloft and let it sail the giant moon’s frigid air. Powered and warmed by a nuclear battery, it will explore Titan for a nominal three-year mission, examining its brutally cold surface and atmosphere. It will even look for signs of extraterrestrial life—or at least its precursors.

“Ambitious” may be too small a word for Dragonfly.

Titan is a world well worth our attention. At roughly 5,150 kilometers wide, it’s the solar system’s second-largest moon (Jupiter’s Ganymede is slightly larger), and it’s bigger than Mercury. Sans Saturn, we might be tempted to call Titan a planet on its own. It’s the only moon known to have a dense atmosphere, with a surface pressure about 1.5 times that of Earth’s. And much like Earth’s atmosphere, Titan’s air is mostly nitrogen, albeit with small and distinctly unearthly amounts of methane and hydrogen. The moon’s cryogenic cold is what really makes it alien: Titan’s surface temperature is about –180 degrees Celsius, so it’s a bit chillier than home. That’s so cold, in fact, that water there is as solid as granite here on Earth.