A big, little moon
The largest of Saturn's moons, Titan, is larger than the planet Mercury. The Cassini spacecraft took this image of Titan in front of Saturn and its rings in 2012.
Exploring the system
The Cassini spacecraft arrived in the Saturn system in 2004 and made more than 12 years of observations before its final orbit in 2017.
Targeted for exploration
Titan is larger than the planet Mercury, It has a dense atmosphere of mainly nitrogen and is the only place in the solar system, apart from earth, with seas of liquid at the surface.
Strange seas of Titan
Deploying Huygens lander
Huygens studied the clouds and atmosphere of the moon during its two-and-a-half hour decent and landed on solid ground, sending 350 photographs and other data to the Cassini spacecraft in orbit around Saturn.
A frozen landscape
Surveying freezing oceans
If the mission goes ahead, the submarine would arrive on Titan in the late 2030s or early 2040s.
Tools for creating
The researchers were concerned that heat from the submarine's power source would create bubbles of dissolved nitrogen from the atmosphere, which could blind the onboard cameras or prevent the sub's buoyancy and propulsion system from working properly.