Colonization of the outer Solar System Colonization of the outer Solar System Many parts of the outer Solar System have been considered for possible future colonization. Most of the larger moons of the outer planets contain water ice, liquid water, and organic compounds that might be useful for sustaining human life. Colonies in the outer Solar System could also serve as centers for long-term investigation of the planet and the other moons. In particular, robotic devices could be controlled by humans without the very long time delays incurred in communicating with Earth. There have also been proposals to place robotic aerostats in the upper atmospheres of
Extraterrestrial liquid water Should planetary mass objects be present, a single, gas giant planet, with or without planetary mass moons, orbiting close to the circumstellar habitable zone, could prevent the necessary conditions from occurring in the system. However, it would mean that planetary mass objects, such as the icy bodies of the solar system, could have abundant quantities of liquid within them. Lunar maria are vast basaltic plains on the Moon that were thought to be bodies of water by early astronomers, who referred to them as "seas". Galileo expressed some doubt about the lunar 'seas' in his "Dialogue Concerning the Two Chief