The Huygens probe didn't last long. What are the challenges of operating a rover on the surface of Titan for at least a few months and what technologies would be used to overcome these?
Titan's atmosphere is not extremely thick. Its only 1.5 bars at ground level. Its also not corrosive, consisting mostly of nitrogen and, to a lesser degree, methane.
The only real challenge is the distance from the sun. Reaching Titan requires a considerable amount of delta-v (about 20km/s from the earth's surface). Once you are on Titan, solar panels are unusable because of the low amount of light that reaches the surface (0.1% of the level at the earth's surface). Also because of this low energy input, temperatures are frigid cold, at about -180°C.
Space is also cold out there, but the atmospheric temperature is worse, because in space there is no convection. Heat can only be exchanged by radiation. In Titan's atmosphere, there is lots of convection, quickly cooling the spacecraft below the allowable temperatures of sensitive equipment, such as the batteries.
The only way to keep a spacecraft operating and supplied with energy for a longer period of time on Titan would be a nuclear power source. A nuclear reactor is possible, but it makes more sense to use a large radioisotope thermoelectric generator (RTG). Therein the heat from the decay of a plutonium ingot is converted to electrical power. RTGs have been used other space missions, such as Voyager or Curiosity, but in order to keep a titan probe warm, you would need a big one, and that makes it expensive to build and launch.
The required size, of course, depends on the amount of insulation, so its an optimization problem: Save some weight on the RTG, and carry more insulation, or carry a larger RTG and save some weight on the insulation.
Additional to @Rikki's answer in addition to heat and power you need to be able to move and explore, there are several challenges to this:
- Titan is far from the sun, so has very little light. On Mars there's enough light for conventional camera instruments to work. Making navigation decisions is possible based mostly on visual information. On titan you'd need to design a system that can "see" terrain in a very dark environment
- Titan is very far away from earth, so communications takes a great deal of time. It's unrealistic for a titan rover to be directed from earth as nothing would get done, so the rover would need to be able to navigate and use its science instruments with a great deal of autonomy, which means a high level of AI
- Parts of Titan are covered with liquid hydrocarbons in which a rover would easily get mired. It is theorized that it rains hydrocarbons as well, so a rover would need to be able to recognize and avoid seas, rivers, ponds, and puddles of liquid methane which would be a hazard
- We know comparatively little about the surface of Titan. Before committing a rover to the surface of a planetoid we would want to do extensive, accurate mapping of the surface, which would have to be incorporated as part of, or a separate mission to pave the way for a rover mission
So, for a rover to be successful it would need to independently move around largely unknown terrain which is pitch black, close to absolute zero, and covered with liquid hydrocarbon all the while being able to do meaningful science.