NEW YORK: Since the moon landing half a century ago, all space exploration of the planets and moons in our solar system has been on land using rovers. Right now, as a matter of fact, the Curiosity Rover continues to collect data and samples of the Red Planet.
The NASA Innovative Advanced Concepts program is looking forward to developing a robotic submersible vehicle to explore the bodies of water on other celestial bodies. Currently, NASA is developing the Titan Submarine Phase I Conceptual Design which could, one day, venture forth into even the hydrocarbon lakes of the Saturn moon Titan.
Titan has always been a pet project mostly because while it is a moon it does not exhibit the same characteristics as other satellites in our solar system.