For the fourth mission of the “New Frontier” exploration program, Dragonfly, NASA decided to send a 2-meter-long drone to explore Titan, Saturn’s satellite, and the only moon in the Solar System to have an atmosphere. Its mission: to detect traces of life.
Titan is unique in having an abundant, complex, and diverse carbon-rich chemistry on the surface of a water-ice-dominated world with an interior water ocean, making it a high-priority target for astrobiology and origin of life studies. On June 27, 2019, Dragonfly was selected to become the fourth mission in the New Frontiers program.
The New Frontiers program
The New Frontiers program is a series of space exploration missions being conducted by NASA with the purpose of researching several of the Solar System bodies, including the dwarf planet Pluto. NASA is encouraging both domestic and international scientists to submit mission proposals for the program.
New Frontiers was built on the innovative approach used by the Discovery and Explorer Programs of principal investigator-led missions. It is designed for medium-class missions that cannot be accomplished within the cost and time constraints of Discovery, but are not as large as Large Strategic Science Missions (formerly known as Flagship missions or Flagship-class missions, these missions were the costliest and most capable NASA science spacecraft).
There are currently three New Frontiers missions in progress: New Horizons, which was launched in 2006 and reached Pluto in 2015, Juno, which was launched in 2011 and entered Jupiter’s orbit in 2016, and OSIRIS-REx, a NASA asteroid study and sample-return mission launched in September 2016.
Dragonfly, the fourth mission of the “New Frontier” exploration program, is a planned spacecraft and mission that will send a mobile robotic rotorcraft lander to Titan, the largest moon of Saturn, in order to study prebiotic chemistry and extraterrestrial habitability at various locations where it will perform vertical-take-offs and landings.
Dragonfly, a drone soon on Titan
The mission should be launched in 2026 to arrive at its destination eight years later on Titan, the largest moon of Saturn, in 2034. But unlike the missions sent to Mars, it will not be a rover which will explore the satellite, but a drone. Once there, the drone Dragonfly mission will detach from the capsule parachuted in the atmosphere of Titan, activate its eight rotors, and begin an exploration mission planned to last two and a half years.
Due to an atmosphere four times denser and seven times lower than the Earth’s, the American space agency has indeed preferred this new means of exploration for the fourth mission of the “New Frontier” exploration program. The octocopter drone will have to travel more than one hundred and seventy-five kilometres on the surface of the satellite, a distance greater than twice that travelled by the entirety of the rovers deployed on Mars.
The drone, with a wingspan of more than two meters and equipped with eight propellers, will be powered by a radioisotope thermoelectric generator, just like the Martian Curiosity rover. It will embark on board four measuring instruments. Dragonfly is an astrobiology mission to Titan to assess its microbial habitability and study its prebiotic chemistry at various locations. Dragonfly will perform controlled flights and vertical take-offs and landings between locations, while powered by a radioisotope thermoelectric generator.
If NASA chose this mission, it is because Titan is very similar to the early Earth. It has, just like the Earth, oceans on its surface. But these are composed of hydrocarbon, mainly methane, made liquid by the ultra-low temperatures of the satellite, of minus one hundred and eighty degrees Celsius in average. If its atmosphere is, as on Earth, mostly composed of nitrogen, it rains on the other hand methane.
“Visiting this mysterious oceanic world could revolutionise what we know about life in the universe”, said NASA Administrator Jim Bridenstine. The Dragonfly drone will have a well-filled course, made in “bounds” of about nine kilometres: it will arise in particular places to collect samples, equatorial dunes of Shangri-La, which resemble the linear dunes of Namibia, at Selk crater, where there would be liquid water and organic substances, complex molecules that contain carbon, combined with hydrogen, oxygen and nitrogen, essential elements for the appearance of life.
The Dragonfly mission will consist in looking for biochemical processes similar to those that could exist on Earth, even to find signs of life, extinguished or, better still, in activity. “It is remarkable to imagine this drone flying miles and miles across the organic sand dunes of Saturn’s largest moon, examining the processes that have shaped this extraordinary environment”. Dragonfly will explore a world filled with a wide variety organic molecules, which are the bricks of life and could help us break into the origin of life itself.
According to NASA, the thirteen years of data collected by the Cassini-Huygens spacecraft have determined an ideal landing site for the upcoming mission, with stable weather conditions. This mission ended in September 2017: the probe had plunged into the atmosphere of Saturn. Expected to remain four years in orbit around the planet, it had orbited around for thirteen years, not without having placed a probe, Huygens, on the surface of Titan before, as recalled Jean-Pierre Lebreton of ESA: “Huygens was not conceived as a lander; Titan’s surface was unknown. In fact, initially when Huygens was conceived, Titan’s surface was thought to be covered by a global ocean. We could not see through Titan’s atmosphere so we did not know anything about the geology of the surface. Huygens was designed as a parachute descent probe, and the main measurement was done during this two and a half-hour descent. Fortunately, Huygens landed on the surface and Cassini received data for seventy minutes”.
The Cassini probe, thanks to its infrared measuring instrument, made it possible to complete these data by mapping the satellite of Saturn, considered as a proto-Earth. “We also talked about Earth in the freezer” said Jean-Pierre Lebreton; “I’m not sure that’s a good expression, but it turns out that Titan is a very rich world, very dynamic, it’s certainly cold but it is not frozen at all, but it is an extremely dynamic atmosphere, where there is intense fluvial activity. There is a cycle of methane in Titan’s atmosphere and on its surface as there is a water cycle on Earth is a much more fascinating world than the frozen Earth phenomenon we have evoked”.
The mission will involve flights to multiple different locations on the surface, which allows sampling diverse regions and geological contexts. Titan is a compelling astrobiology target because its surface contains abundant complex carbon-rich chemistry and because both liquid water and liquid hydrocarbons can occur on its surface, possibly forming a prebiotic primordial soup.