The majority of Earth is covered in an ocean of liquid water, but the other worlds in our Solar System are a whole lot different. Most don’t have any kind of liquid on their surface, and while we know that there is definitely a liquid ocean under the thick ice of Enceladus, it might pose a big challenge to explore. One of Saturn’s other moons, Titan, is one of the very few objects in the Solar System with liquid right out in the open, and NASA is targeting its seas for a future mission that will send a submarine to explore what lies below.

The biggest challenge for NASA engineers is dealing with the fact that the massive bodies of liquid aren’t water at all, but hydrocarbons such as super-cooled methane. A new paper describing the ongoing research into the potential makeup of the seas, and how NASA’s submarine would need to be designed in order to actually survive in them, was just published in the journal Fluid Phase Equilibria.

“NASA is designing an unmanned submarine to explore the hydrocarbon rich seas of Saturn’s moon Titan,” the researchers write. “Titan is the only known celestial body in our solar system other than Earth with stable liquid seas on its surface. The thermodynamic properties of Titan’s seas have not been well characterized. This work investigates the solubility of nitrogen in varying liquid methane-ethane compositions and the effects of dissolved nitrogen on the density of the sea.”

The team, made up of scientists from the Hydrogen Properties for Energy Research (HYPER) Laboratory at Washington State University, simulated the incredibly frigid temperatures and intense pressure that a vehicle would have to endure while exploring Titan’s seas. They found that observing and recording visual data would be a huge hurdle, as most camera technology simply wouldn’t survive the harsh conditions.

They got around this by using a tool called a borescope, which uses a long, thick cord or rigid tube. The tube acts like an extended optical relay system, and as light enters it travels down the tube before it strikes the objective lens that turns it into an actual image that can be viewed through the eyepiece or, in this case, captured, recorded, and relayed back to Earth. Because the lens itself is separated from the tip of the optical relay it can be protected from the harsh conditions outside the submarine.

There’s still a lot of work to be done before NASA can move forward with its planned mission, but with an actual launch date still two decades away there’s plenty of time to get it right. At least now we know it’ll have functional eyes.