Extraterrestrial liquid water not. Similar indirect evidence, however, supports the existence of liquids below the surface of several moons and dwarf planets elsewhere in the Solar System. Some are speculated to be large extraterrestrial "oceans". Liquid water is thought to be common in other planetary systems, despite the lack of conclusive evidence, and there is a growing list of extrasolar candidates for liquid water. As of December 2015, the confirmed liquid water in the Solar System outside Earth is 25-50 times the volume of Earth's water (1.3 billion cubic kilometers). Water on Mars exists today almost exclusively as ice, with a small amount
Colonization of the outer Solar System perhaps the most advantageous locale in the outer Solar System for colonization. He said, "In certain ways, Titan is the most hospitable extraterrestrial world within the Solar System for human colonization." A widely published expert on terraforming, Christopher McKay, is also a co-investigator on the Huygens probe that landed on Titan in January 2005. The surface of Titan is mostly uncratered and thus inferred to be very young and active, and probably composed of mostly water ice, and lakes of liquid hydrocarbons (methane/ethane) in its polar regions. While the temperature is cryogenic (95 K) it should be able to support