Saturn’s moon Titan is one of the most interesting and least understood bodies in our solar system. It is 50 percent larger than Earth’s moon, larger even than the planet Mercury, and has 80 percent more mass.

Titan has an atmosphere one-and-a-half times as dense as Earth’s and, like Venus, that thick atmosphere makes its surface difficult to study. The atmosphere is primarily made of nitrogen, methane and hydrogen and it is very cold, with temperatures reaching -290 Fahrenheit.

Despite these extreme conditions, it is believed to be the only other body in the solar system with stable liquid surface water. Data from the Voyager, Huygens and Cassini probes have confirmed that there are large polar seas on the surface.

In a document prepared for the 46th Lunar and Planetary Conference, the NASA Innovative Advanced Concepts program has unveiled a theoretical design for a robotic submarine that could be dropped into the moon’s lakes of lakes of liquid methane and ethane.

The most likely target for exploration is Kraken Mare. The toxic sea has a a surface area of 154,000 square miles and reaches depths of 525 feet.

Kracken Mare would present significant engineering challenges. Data gathered to date suggest that the lake has choppy waves and possibly tides. Because of the thick atmosphere and the fact that the would be operating under the lake solar power is also not an option.

According to the design the vehicle would use a piston-driven turbine propulsion system to maneuver and take on liquid from the lake as a ballast. The submarine would weigh about one ton. It’s power would probably come from a radioisotope generator which converts heat from radioactive pellets into electricity. This would produce about 1kW of power and allow the sub to move at speeds of about one meter per second.

Communication with the probe would also be difficult. Titan is 80 light minutes away so, after each comment was received it would take more than 2.5 hours to get a response. It would also be difficult or impossible to communicate with the sub while it was submerged.

Because any sort of real-time remote control of the vehicle would be impossible, the sub would surface for 16 hours per day, send back its data, get new instructions and submerge again.

Although the lakes of Titan would be toxic to human life, it is not impossible for life to exist there. In 2010 microbial life was found in a natural hot liquid asphalt in Trinidad and Tobago. So, we know that life can exist even in extreme conditions that humans would find impossible and where life exists, evolution can take place.

“Measurement of the trace organic components of the sea, which perhaps may exhibit prebiotic chemical evolution, will be an important objective, and a benthic sampler (a robotic grabber to sample sediment) would acquire and analyze sediment from the seabed. These measurements, and seafloor morphology via sidescan sonar, may shed light on the historical cycles of filling and drying of Titan’s seas. Models suggest Titan’s active hydrological cycle may cause the north part of Kraken to be ‘fresher’ (more methane-rich) than the south, and the submarine’s long traverse will explore these composition variations,” said the authors of the conceptual document.

This is not the first craft for Titan proposed by NASA’s Innovative Advanced Concepts program (NIAC). The group explores ideas and makes suggestions independent of NASA’s current priorities. In 2010 the NIAC proposed a boat for Titan, another boat was proposed in 2012 and a “squishable” robot in 2013.

At the moment, NASA has its hands full with missions to Mars and Jupiter’s moon Europa but when the space agency is ready to take on new challenge, the NIAC has no shortage of suggestions.