Colonization of the outer Solar System elsewhere in the Solar System, perhaps via the proposed Interplanetary Transport Network, may be feasible in the not-so-distant future. This could make colonization of the Moon, Mercury and main-belt asteroids more practical. Robert Zubrin identified Saturn, Uranus and Neptune as "the Persian Gulf of the Solar System", as the largest sources of deuterium and helium-3 to drive a fusion economy, with Saturn the most important and most valuable of the three, because of its relative proximity, low radiation, and excellent system of moons. Zubrin identified Titan as possessing an abundance of all the elements necessary to support life, making Titan
Moons of Jupiter Moons of Jupiter There are 79 known moons of Jupiter. This gives Jupiter the largest number of moons with reasonably stable orbits of any planet in the Solar System. The most massive of the moons are the four Galilean moons, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. From the end of the 19th century, dozens of much smaller Jovian moons have been discovered and have received the names of lovers or daughters of the Roman god Jupiter or