The siren call of Titan could not be ignored. NASA’s next billion-dollar mission, called Dragonfly, will be an innovative quadcopter to explore Titan, Saturn’s largest moon, the agency announced today. The craft will soar and hover over the icy moon’s surface—and land on it—in a search for the conditions and chemistry that could foster life.
The mission—led by Elizabeth “Zibi” Turtle, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, and also managed by APL—will launch in 2026. It represents a calculated risk for the agency, embracing a new paradigm of robotic exploration to be used on a distant moon. “Titan is unlike any other place in the solar system, and Dragonfly is like no other mission,” said Thomas Zurbuchen, NASA’s associate administrator for science in Washington, D.C., while announcing the mission’s selection. “The science is compelling. It’s the right time to do it.”
Titan is veiled by a nitrogen atmosphere and larger than Mercury. It is thought to harbor a liquid ocean beneath its frozen crust of water ice. NASA’s Cassini spacecraft studied Titan during its historic campaign, and, in 2005, dropped the short-lived Huygens probe into Titan’s atmosphere.
The surface it saw had many geologic features similar to those found on Earth, including plateaus, dune-filled deserts, and, at its poles, liquid seas and rivers. But on Titan, where temperatures average a frigid 94 K, the “rocks” are made of water ice and the seas are filled with ethane and methane, hydrocarbons that are gases on Earth. The moon’s stew of organic molecules and water, many scientists believe, could have resulted in reactions to create amino acids and the bases used to build DNA’s double helix. It’s as if Titan has been conducting experiments on life formation for millions of years, Turtle says. “Dragonfly is designed to go pick up the results of those experiments and study them.”
Dragonfly is an inspiring selection, adds Lindy Elkins-Tanton, a planetary scientist at Arizona State University in Tempe and principal investigator of Psyche, NASA’s mission to a metallic asteroid. “Titan might truly be the cradle for some kind of life—and whether life has emerged or not, Titan’s hydrocarbon rivers and lakes, and its hydrocarbon snow, makes it one of the most fantasylike landscapes in our solar system.”
Given Titan’s complex surface, a lander at a single site would not be able to say much about the moon’s chemistry. Dragonfly leverages the advances in computing and aircraft design that have led to the explosion of hovering drones on Earth. It will carry eight rotor blades, on the top and bottom of each of four arms. It is, in effect, a movable lander, capable of shunting kilometers between sampling sites every 16 Earth days. Titan’s dense air and low gravity will allow the 300-kilogram, sedan-size copter, which will be powered by a radioactive generator, to hover with 38 times less power than needed on Earth.
The timing of Dragonfly’s arrival, in 2034 during Titan’s long northern winter, ruled out a landing near the north pole, home to the moon’s evocative methane seas; those sites would leave it unable to radio home. Instead, the quadcopter will explore the moon’s vast equatorial deserts, which are likely fed by a grab bag of material from all over the moon. (“The largest zen garden in the solar system,” Turtle says.) It will search especially for impact craters or ice volcanoes, energetic processes that could provide a spark—and the liquid water—needed for nascent organic chemistry. During its nearly 3-year primary mission, after traveling 175 kilometers in a series of flights lasting up to 8 kilometers each, Dragonfly will ultimately reach the 80-kilometer-wide Selk impact crater, its primary target. The impact that created Selk was large enough to melt Titan’s water-ice crust and liberate oxygen, priming reactions that are recorded in its outcrops.
Dragonfly won’t be equipped with a robotic arm, like the recent Mars rovers. Its exploration will first be guided by an instrument on its belly that will bombard the ground with neutron radiation, using the gamma rays this attack releases to differentiate between basic terrain types, such as ammonia-rich ice or carbon-rich sand dunes. Its two landing skids will also each carry a rotary-percussive drill capable of taking samples and feeding them through a pneumatic tube to a mass spectrometer that can analyze their composition. The sampling system represented a risk for the mission; NASA scientists were concerned Titan’s hydrocarbon-rich atmosphere could clog it, Zurbuchen says. “It’s the oil spill version of an atmosphere.” Over the past 2 years, after extensive testing with “pathological” materials and a redesign, Turtle says, the agency’s fears were allayed.
Beyond Titan’s surface, Dragonfly will also target its atmosphere and interior. During flight, it can collect measurements, much like instruments mounted on a balloon would. And it is also equipped with a seismometer that could use vibrations induced on the moon by its tidal lock with Saturn to gauge the ocean hidden beneath its crust, which scientists have suggested could be made up of ammonia-water or water and sulfate. Ultimately, the quadcopter’s explorations may be able to last up to 8 years after landing before its nuclear power source peters out.
The cost-capped New Frontiers program, with $850 million set for the mission and some $150 million for launch, is the largest planetary exploration line that NASA opens to outside competition and leadership. A significant factor in Dragonfly’s selection, Zurbuchen adds, was APL’s ability to deliver the Parker Solar Probe, now on a mission to explore the sun that's on time and under budget. Dragonfly went head-to-head with one other finalist, the Comet Astrobiology Exploration Sample Return, which would have sampled primordial ice from a comet and returned it for study on Earth.
Previous spacecraft launched under New Frontiers include New Horizons, which surveyed Pluto and recently flew by MU69, an icy object in the farthest reaches of the solar system; Juno, now in orbit around Jupiter; and the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer, now orbiting the asteroid Bennu before collecting samples and returning them to Earth.
