Dragonfly: The billion-mile mission to explore Saturn’s biggest moon

There are many reasons to attend a scientific conference. You get to see collaborators and friends who are pushing new projects forward. You get to watch lots of cool talks updating you on the latest cool results in your research domain. And then it happens, every now and then, that you attend some big talk on a subject you know nothing about and come out staggered. That’s what happened to me this week at the 2024 Astrobiology Conference (or AbSciCon) where I learned about NASA’s Dragonfly mission to Saturn’s giant moon Titan.

AbSciCon is a big conference. It happens once every two years with multiple concurrent sessions running on all kinds of topics — everything from the origin of life to the nature of evolution to the physics of exoplanets. My colleagues and I had fun presenting a bunch of new research results. But what I love about this conference is the opportunity to learn so much about so many different fields. Most of the talks are short, 15-minute affairs that give you just a taste of a scientist’s work. It’s the hour-long plenary talks in the morning, however, that really give you a deep dive into a topic. That’s when my mind was blown by Dragonfly.

Exploring Titan

Let’s pull back a bit so you can see what I’m talking about. Titan is the largest moon orbiting the gas giant planet Saturn. It’s actually the second-biggest moon in the whole Solar System. What really sets Titan apart, however, is that it’s the only moon with a real atmosphere. Titan hosts a thick layer of gas made mostly of Nitrogen but also with enough Methane to make things interesting. The interaction of the methane with sunlight renders the surface of Titan invisible underneath an opaque haze. In the early 2000s, NASA’s Cassini probe arrived at Saturn and spent a lot of time investigating Titan, including dropping a probe to its surface. What planetary scientists discovered from these studies was that Titan may be the most interesting place in the Solar System, after Earth, when it comes to thinking about life.

Like many outer moons, Titan has tremendous amounts of water, including a subsurface ocean. The combination of so much water, methane, and other compounds leads to remarkable behavior like ethane/methane rain, which collects into vast lakes of liquid methane. Titan is, in fact, the only world that has liquids flowing stably on its surface. Images of the moon taken over time show evidence of a rich methane/ethane cycle of evaporation, rain, runoff, and collection into extended bodies like the lakes. The temperatures on Titan are, however, pretty low (-290) because Saturn is so far from the Sun. Despite these icebox conditions, there’s so much interesting organic chemistry happening on Titan that scientists think it could be a great place to understand alternative biochemistries, i.e. alien life. 

That’s where Dragonfly comes in. The mission, approved by NASA in 2019, will send a quadcopter to Titan to explore the enigmatic moon. Yes, you read that right. We’re sending a flying laboratory to an alien, haze-covered moon that’s about 1 billion miles away. This is nothing short of science fiction, yet the mission is well along already. It’s slated to launch in just four years and should arrive at Titan in 2034. At this stage, however, the technical challenges, the solutions NASA scientists are finding, and the possibilities of what Dragonfly will achieve are what left my head spinning.

Dragonfly’s challenges

The first issue NASA scientists face is control. After its descent to the surface, the quadcopter will begin its exploration of Titan by flying a few kilometers and then staying put for 16 days or so to take measurements. But Titan is so far from Earth that light signals take about an hour to make a one-way journey. That means Dragonfly must do all of its actual flying without human oversight. It’s an autonomous flying drone. Yikes! Luckily, NASA scientists have learned a lot about autonomous piloting from various Mars missions (including the remarkable Ingenuity Mars helicopter). Still, Dragonfly takes the question of AI-directed airborne exploration to entirely new levels.

Next comes the science experiments packed into Dragonfly. The mission will measure everything from the chemical composition of Titan’s “soil” to climatic conditions to seismographic studies, which might reveal details about Titan’s subsurface oceans. But all of Dragonfly’s complex experimental machinery has to work at Titan’s simultaneously low temperatures and relatively atmospheric high pressures. This presents an enormous technical challenge that NASA engineers are working hard to solve.

The most startling thing to me was Dragonfly’s size. For something going so far, it’s really big. Dragonfly is about the size of a Minivan (12.5 ft long, 5.5 ft high) and weighs almost 1,900 lbs. That’s a big drone to send to another planet. Luckily, thanks to Titan’s low gravity and thick atmosphere, it’s not hard to get something as massive as Dragonfly airborne. 

Across its three-year mission, scientists hope to use Dragonfly to explore more than 100 miles of Titan’s strange surface. It’s a hugely ambitious mission — and one you need to keep your eyes on. Human beings can do a lot of terrible things and they can do a lot of amazing things. Dragonfly falls into the second category, and we should celebrate that.