These conditions together could create a habitable environment, and could persist for several hundred million years. [195] It has also been hypothesized that liquid-ammonia oceans could exist deep below the surface. [183], As NASA notes in its news article on the June 2010 findings: "To date, methane-based life forms are only hypothetical. [78] There are dark areas of similar size elsewhere on Titan, observed from the ground and by Cassini; at least one of these, Ligeia Mare, Titan's second-largest sea, is almost a pure methane sea. [79][80], The possibility of hydrocarbon seas on Titan was first suggested based on Voyager 1 and 2 data that showed Titan to have a thick atmosphere of approximately the correct temperature and composition to support them, but direct evidence was not obtained until 1995 when data from Hubble and other observations suggested the existence of liquid methane on Titan, either in disconnected pockets or on the scale of satellite-wide oceans, similar to water on Earth. Titan is about 759,000 miles (1.2 million kilometers) from Saturn, which itself is about 886 million miles (1.4 billion kilometers) from the Sun, or about 9.5 astronomical units (AU). The surface of Titan has been described as "complex, fluid-processed, [and] geologically young". Titan is primarily composed of ice and rocky material, which is likely differentiated into a rocky core surrounded by various layers of ice, including a crust of ice Ih and a subsurface layer of ammonia-rich liquid water. [28] Based on its bulk density of 1.88 g/cm3, Titan's composition is half water ice and half rocky material. The density of Titan is consistent with a body that is about 60% rock and 40% water. In addition, amino acids, the building blocks of protein were found. [154], The Huygens probe landed just off the easternmost tip of a bright region now called Adiri. [151] Liquid has been found in abundance on the surface in the north polar region, in the form of many lakes and seas discovered by Cassini. [147] It took images of Titan, including Titan and Saturn together in mid to late 1979. Current understanding is that the hills (also referred to as highlands) are composed mainly of water ice. [74][75] Examination has also shown the surface to be relatively smooth; the few objects that seem to be impact craters appeared to have been filled in, perhaps by raining hydrocarbons or volcanoes. There is also evidence that Titan's ice shell may be substantially rigid,[36][37] which would suggest little geologic activity. Pop Culture. This is likely the first direct evidence of the presence of liquid channels on Titan and the first observation of hundred-meter deep canyons on Titan. Titan's surface is thought to be a poor reflector of extremely-low-frequency radio waves, so they may instead be reflecting off the liquid–ice boundary of a subsurface ocean. Located in the Mithrim Montes range, it is 3,337 m tall. [85] Following a flyby on July 22, 2006, in which the Cassini spacecraft's radar imaged the northern latitudes (that were then in winter), several large, smooth (and thus dark to radar) patches were seen dotting the surface near the pole. That degree of warping suggests that Titan's interior is relatively deformable, and that the most likely model of Titan is one in which an icy shell dozens of kilometres thick floats atop a global ocean. [57] This is the first time propene has been found on any moon or planet other than Earth and is the first chemical found by the CIRS. [133][135][138] Studies of dunes' composition in May 2008 revealed that they possessed less water than the rest of Titan, and are thus most likely derived from organic soot like hydrocarbon polymers clumping together after raining onto the surface. They are washed down the hills with the methane rain and are deposited on the plains over geological time scales.[155]. Alternatively, the lineaments may be liquid-formed channels, suggesting old terrain that has been cut through by stream systems. [81], The Cassini mission confirmed the former hypothesis. [198], In 2005, astrobiologist Chris McKay argued that if methanogenic life did exist on the surface of Titan, it would likely have a measurable effect on the mixing ratio in the Titan troposphere: levels of hydrogen and acetylene would be measurably lower than otherwise expected. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the southern summer generate uplift in the atmosphere, resulting in convection. [31], A mountain range measuring 150 kilometers (93 mi) long, 30 kilometers (19 mi) wide and 1.5 kilometers (0.93 mi) high was also discovered by Cassini in 2006. Though many phenomena were suggested to explain this fluctuation, the lava flows were found to rise 200 meters (660 ft) above Titan's surface, consistent with it having been erupted from beneath the surface. Even so, despite saying that a non-biological catalytic explanation would be less startling than a biological one, McKay noted that the discovery of a catalyst effective at 95 K (−180 °C) would still be significant.