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93-479: The length of the lake from north to south is 45 kilometers (28 mi) and the widest distance between east and west is only 6 kilometers (3.7 mi). The area is 95 km (37 sq mi) and the storage capacity is 1.63 billion m. The south part of lake is shallow with the deepest place in the northern part at 62 meters (203 ft). The winter average temperature in Heilongjiang Province

186-556: A Phase II grant to a design study of a Titan Submarine to explore the seas of Titan. Titan is thought to be a prebiotic environment rich in complex organic compounds , but its surface is in a deep freeze at −179 °C (−290.2 °F; 94.1 K) so it is currently understood that life cannot exist on the moon's frigid surface. However, Titan seems to contain a global ocean beneath its ice shell, and within this ocean, conditions are potentially suitable for microbial life. Climate of Titan The climate of Titan ,

279-485: A cumulative surface area of 215,000 square kilometres (83,000 sq mi). Lakes in Titan's lower-latitude and equatorial regions have been proposed, though none have been confirmed; seasonal or transient equatorial lakes may pool following large rainstorms. Cassini RADAR data has been used to conduct bathymetry of Titan's seas and lakes. Using detected subsurface reflections, the measured maximum depth of Ligeia Mare

372-559: A distance of about 85 centimeters from Huygens . There is evidence of erosion at the base of the rocks, indicating possible fluvial activity. The ground surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. In March 2007, NASA, ESA, and COSPAR decided to name the Huygens landing site the Hubert Curien Memorial Station in memory of the former president of

465-413: A high orbital eccentricity not immediately explained by co-accretion alone. A proposed model for the formation of Titan is that Saturn's system began with a group of moons similar to Jupiter's Galilean moons, but that they were disrupted by a series of giant impacts , which would go on to form Titan. Saturn's mid-sized moons, such as Iapetus and Rhea , were formed from the debris of these collisions. Such

558-556: A much lower temperature of about 94 K (−179 °C; −290 °F). Due to these factors, Titan is called the most Earth-like celestial object in the Solar System. The Dutch astronomer Christiaan Huygens discovered Titan on March 25, 1655. Fascinated by Galileo 's 1610 discovery of Jupiter's four largest moons and his advancements in telescope technology, Huygens, with the help of his elder brother Constantijn Huygens Jr. , began building telescopes around 1650 and discovered

651-405: A robotic space probe to Titan. Initial conceptual work has been completed for such missions by NASA (and JPL ), and ESA . At present, none of these proposals have become funded missions. The Titan Saturn System Mission (TSSM) was a joint NASA/ ESA proposal for exploration of Saturn 's moons. It envisions a hot-air balloon floating in Titan's atmosphere for six months. It was competing against

744-488: A significant atmosphere was first suspected by Catalan astronomer Josep Comas i Solà , who observed distinct limb darkening on Titan in 1903. Due to the extensive, hazy atmosphere, Titan was once thought to be the largest moon in the Solar System until the Voyager missions revealed that Ganymede is slightly larger. The haze also shrouded Titan's surface from view, so direct images of its surface could not be taken until

837-431: A single enormous Hadley cell . Warm gas rises in Titan's southern hemisphere—which was experiencing summer during Huygens ' descent—and sinks in the northern hemisphere, resulting in high-altitude gas flow from south to north and low-altitude gas flow from north to south. Such a large Hadley cell is only possible on a slowly rotating world such as Titan. The pole-to-pole wind circulation cell appears to be centered on

930-447: A surface crust. The presence of ammonia allows water to remain liquid even at a temperature as low as 176 K (−97 °C) (for eutectic mixture with water). The Cassini probe discovered evidence for the layered structure in the form of natural extremely-low-frequency radio waves in Titan's atmosphere. Titan's surface is thought to be a poor reflector of extremely-low-frequency radio waves, so they may instead be reflecting off

1023-450: A violent beginning would also explain Titan's orbital eccentricity. A 2014 analysis of Titan's atmospheric nitrogen suggested that it was possibly sourced from material similar to that found in the Oort cloud and not from sources present during the co-accretion of materials around Saturn. Titan orbits Saturn once every 15 days and 22 hours. Like Earth's Moon and many of the satellites of

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1116-587: Is about 90.6 K (-182.55 °C, or -296.59 °F). At this temperature water ice has an extremely low vapor pressure, so the atmosphere is nearly free of water vapor. However the methane in the atmosphere causes a substantial greenhouse effect which keeps the surface of Titan at a much higher temperature than what would otherwise be the thermal equilibrium. Haze in Titan's atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, making its surface significantly colder than its upper atmosphere. This partially compensates for

1209-502: Is below -20°C (-4°F), but the temperature at the bottom of the water is always above 10°C (50°F). On Titan , the largest moon of the planet Saturn , there is a large surface body of liquid hydrocarbons , Jingpo Lacus , named after Jingpo Lake. The lake was created about 10,000 years ago when the lava of volcanic eruptions in the region blocked the flow of the Mudan River . Jingpo Lake has experienced five volcanic eruptions. It

1302-459: Is consistent with 49% CH 4 , 41% C 2 H 6 , and 10% N 2 by volume. As Titan is synchronously locked with Saturn, there exists a permanent tidal bulge of roughly 100 metres (330 ft) at the sub- and anti-Saturnian points. Titan's orbital eccentricity means that tidal acceleration varies by 9%, though the long orbital period means that these tidal cycles are very gradual. A team of researchers led by Ralph D. Lorenz evaluated that

1395-906: Is covered by plains. Of the several types of plains observed, the most extensive are the Undifferentiated Plains that encompass vast, radar-dark uniform regions. These mid-latitude plains—located largely between 20 and 60° north or south—appear younger than all major geological features except dunes and several craters. The Undifferentiated Plains likely were formed by wind-driven processes and composed of organic-rich sediment. Another extensive type of terrain on Titan are sand dunes, grouped together into vast dune fields or "sand seas" located within 30° north or south. Titanian dunes are typically 1–2 kilometres (0.62–1.24 mi) wide and spaced 1–4 kilometres (0.62–2.49 mi) apart, with some individual dunes over 100 kilometres (62 mi) in length. Limited radar-derived height data suggests that

1488-474: Is four times as thick as Earth's, making it difficult for astronomical instruments to image its surface in the visible light spectrum. The Cassini spacecraft used infrared instruments, radar altimetry and synthetic aperture radar (SAR) imaging to map portions of Titan during its close fly-bys. The first images revealed a diverse geology, with both rough and smooth areas. There are features that may be volcanic in origin, disgorging water mixed with ammonia onto

1581-557: Is how long it takes Titan to orbit Saturn. Titan is tidally locked , so the same part of Titan always faces Saturn, and there is no separate "month" cycle. Seasonal change is driven by Saturn's year: it takes Saturn about 29.5 Earth years to orbit the Sun, exposing different amounts of sunlight to Titan's northern and southern hemispheres during different parts of the Saturnian year. Seasonal weather changes include larger hydrocarbon lakes in

1674-468: Is known to condense in Titan's atmosphere , the cloud was more likely to be ethane, as the detected size of the particles was only 1–3 micrometers and ethane can also freeze at these altitudes. In December, Cassini again observed cloud cover and detected methane, ethane and other organics. The cloud was over 2400 km in diameter and was still visible during a following flyby a month later. One hypothesis

1767-610: Is larger than Mercury ; yet Titan is only 40% as massive as Mercury, because Mercury is mainly iron and rock while much of Titan is ice, which is less dense. Discovered in 1655 by the Dutch astronomer Christiaan Huygens , Titan was the first known moon of Saturn and the sixth known planetary satellite (after Earth's moon and the four Galilean moons of Jupiter). Titan orbits Saturn at 20 Saturn radii or 1,200,000 km above Saturn's apparent surface. From Titan's surface, Saturn subtends an arc of 5.09 degrees, and if it were visible through

1860-415: Is locked in a 3:4 orbital resonance with Titan—that is, Hyperion orbits three times for every four times Titan orbits. Hyperion probably formed in a stable orbital island, whereas the massive Titan absorbed or ejected any other bodies that made close approaches. Titan is 5,149.46 kilometres (3,199.73 mi) in diameter; it is 6% larger than the planet Mercury and 50% larger than Earth's Moon . Titan

1953-435: Is low, typically no more than 150 meters. Occasional elevation changes of 500 meters have been discovered and Titan has mountains that sometimes reach several hundred meters to more than 1 kilometer in height. Titan's surface is marked by broad regions of bright and dark terrain. These include Xanadu , a large, reflective equatorial area about the size of Australia. It was first identified in infrared images from

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2046-456: Is roughly 200 metres (660 ft), and that of Ontario Lacus is roughly 90 metres (300 ft). Titan's lakes and seas are dominated by methane ( CH 4 ), with smaller amounts of ethane ( C 2 H 6 ) and dissolved nitrogen ( N 2 ). The fraction of these components varies across different bodies: observations of Ligeia Mare are consistent with 71% CH 4 , 12% C 2 H 6 , and 17% N 2 by volume; whilst Ontario Lacus

2139-478: Is that it is currently raining (or, if cool enough, snowing) on the north pole; the downdrafts at high northern latitudes are strong enough to drive organic particles towards the surface. These were the strongest evidence yet for the long-hypothesized "methanological" cycle (analogous to Earth's hydrological cycle ) on Titan. Clouds have also been found over the south polar region. While typically covering 1% of Titan's disk, outburst events have been observed in which

2232-494: Is that methane rains onto the poles in winter and evaporates in summer. According to a paper by Tetsuya Tokano of the University of Cologne, cyclones driven by this evaporation and involving rain as well as gale-force winds of up to 20 m/s (45 mph) are expected to form over the large northern seas (Kraken Mare, Ligeia Mare, Punga Mare) only in the northern summer, lasting up to ten days. Calculations suggest that, as

2325-559: Is the largest alpine lava barrier lake in China. This Heilongjiang location article is a stub . You can help Misplaced Pages by expanding it . Titan (moon) Stratosphere : 98.4% nitrogen ( N 2 ), 1.4% methane ( CH 4 ), 0.2% hydrogen ( H 2 ); Titan is the largest moon of Saturn and the second-largest in the Solar System . It is the only moon known to have an atmosphere denser than

2418-623: Is the tenth-largest object known in the Solar system, including the Sun . Before the arrival of Voyager 1 in 1980, Titan was thought to be slightly larger than Ganymede , which has a diameter 5,262 kilometres (3,270 mi), and thus the largest moon in the Solar System. This was an overestimation caused by Titan's dense, opaque atmosphere, with a haze layer 100–200 kilometers above its surface. This increases its apparent diameter. Titan's diameter and mass (and thus its density) are similar to those of

2511-496: The Cassini–Huygens mission in 2004 provided new information, including the discovery of liquid hydrocarbon lakes in Titan's polar regions and the discovery of its atmospheric super-rotation . The geologically young surface is generally smooth, with few impact craters , although mountains and several possible cryovolcanoes have been found. The atmosphere of Titan is mainly nitrogen and methane ; minor components lead to

2604-426: The Cassini–Huygens mission in 2004. The primary constituents of Titan's atmosphere are nitrogen, methane, and hydrogen. The precise atmospheric composition varies depending on altitude and latitude due to methane cycling between a gas and a liquid in Titan's lower atmosphere—the methane cycle. Nitrogen is the most abundant gas, with a concentration of around 98.6% in the stratosphere that decreases to 95.1% in

2697-497: The Earth 's and is the only known object in space—other than Earth —on which there is clear evidence that stable bodies of liquid exist. Titan is one of seven gravitationally rounded moons of Saturn and the second-most distant among them. Frequently described as a planet-like moon , Titan is 50% larger in diameter than Earth's Moon and 80% more massive. It is the second-largest moon in the Solar System after Jupiter's Ganymede and

2790-657: The Europa Jupiter System Mission (EJSM) proposal for funding. In February 2009 it was announced that ESA/NASA had given the EJSM mission priority ahead of the TSSM. The proposed Titan Mare Explorer (TiME) was a low-cost lander that would splash down in Ligeia Mare in Titan's northern hemisphere. The probe would float whilst investigating Titan's hydrocarbon cycle, sea chemistry, and Titan's origins. It

2883-695: The Hubble Space Telescope in 1994, and later viewed by the Cassini spacecraft. The convoluted region is filled with hills and cut by valleys and chasms. It is criss-crossed in places by dark lineaments—sinuous topographical features resembling ridges or crevices. These may represent tectonic activity, which would indicate that Xanadu is geologically young. Alternatively, the lineaments may be liquid-formed channels, suggesting old terrain that has been cut through by stream systems. There are dark areas of similar size elsewhere on Titan, observed from

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2976-571: The Titans , a race of immortals in Greek mythology . The regular moons of Jupiter and Saturn likely formed via co-accretion , similar to the process believed to have formed the planets in the Solar System. As the young gas giants formed, they were surrounded by discs of material that gradually coalesced into moons. While the four Galilean moons of Jupiter exist in highly regular, planet-like orbits, Titan overwhelmingly dominates Saturn's system and has

3069-475: The giant planets , its rotational period (its day) is identical to its orbital period; Titan is tidally locked in synchronous rotation with Saturn, and permanently shows one face to the planet. Longitudes on Titan are measured westward, starting from the meridian passing through this point. Its orbital eccentricity is 0.0288, and the orbital plane is inclined 0.348 degrees relative to the Saturnian equator. The small and irregularly shaped satellite Hyperion

3162-446: The 2009 equinox, with the southern pole entering winter and the north entering summer, it is hypothesised that this vortex could mark the formation of a new, southern polar hood. Titan's clouds, probably composed of methane , ethane , or other simple organics, are scattered and variable, punctuating the overall haze. In September 2006, Cassini imaged a large cloud at a height of 40 km over Titan's north pole. Although methane

3255-669: The ESA. The Dragonfly mission, developed and operated by the Johns Hopkins Applied Physics Laboratory , will launch in July 2028. It consists of a large drone powered by an RTG to fly in the atmosphere of Titan as New Frontiers 4. Its instruments will study how far prebiotic chemistry may have progressed. The mission is planned to arrive at Titan in the mid-2030s. There have been several conceptual missions proposed in recent years for returning

3348-518: The Jovian moons Ganymede and Callisto . Based on its bulk density of 1.881 g/cm , Titan's composition is 40–60% rock, with the rest being water ice and other materials. Titan is probably partially differentiated into distinct layers with a 3,400-kilometre (2,100 mi) rocky center. This rocky center is believed to be surrounded by several layers composed of different crystalline forms of ice, and/or water. The exact structure depends heavily on

3441-587: The TiME probe would be that TALISE is envisioned with its own propulsion system and would therefore not be limited to simply drifting on the lake when it splashes down. A Discovery Program contestant for its mission #13 is Journey to Enceladus and Titan (JET), an astrobiology Saturn orbiter that would assess the habitability potential of Enceladus and Titan. In 2015, the NASA Innovative Advanced Concepts program (NIAC) awarded

3534-500: The Titan flyby if Voyager 1 had been unable to, did not pass near Titan and continued on to Uranus and Neptune. The Cassini–Huygens spacecraft reached Saturn on July 1, 2004, and began the process of mapping Titan's surface by radar . A joint project of the European Space Agency (ESA) and NASA , Cassini–Huygens proved a very successful mission. The Cassini probe flew by Titan on October 26, 2004, and took

3627-477: The Undifferentiated Plains. Titan is never visible to the naked eye, but can be observed through small telescopes or strong binoculars. Amateur observation is difficult because of the proximity of Titan to Saturn's brilliant globe and ring system; an occulting bar, covering part of the eyepiece and used to block the bright planet, greatly improves viewing. Titan has a maximum apparent magnitude of +8.2, and mean opposition magnitude 8.4. This compares to +4.6 for

3720-510: The atmosphere, and obtain a precise measurement of Titan's mass. Atmospheric haze prevented direct imaging of the surface, though in 2004 intensive digital processing of images taken through Voyager 1 's orange filter did reveal hints of the light and dark features now known as Xanadu and Shangri-la , which had been observed in the infrared by the Hubble Space Telescope. Voyager 2 , which would have been diverted to perform

3813-594: The authors of the analysis comparing them to terrestrial fold belts indicative of horizontal compression or convergence. They note that the global distribution of Titan's ridges could be indicative of global contraction, with a thickened ice shell causing regional uplift. The identification of cryovolcanic features on Titan remains controversial and inconclusive, primarily due to limitations of Cassini imagery and coverage. Cassini RADAR and VIMS imagery revealed several candidate cryovolcanic features, particularly flow-like terrains in western Xanadu and steep-sided lakes in

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3906-400: The breakup of methane by the Sun's ultraviolet light, producing a thick orange smog. Energy from the Sun should have converted all traces of methane in Titan's atmosphere into more complex hydrocarbons within 50 million years—a short time compared to the age of the Solar System. This suggests that methane must be replenished by a reservoir on or within Titan itself. The ultimate origin of

3999-457: The cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the Titanean summer generate uplift in the atmosphere, resulting in convection . This explanation is complicated by the fact that cloud formation has been observed not only post–summer solstice but also at mid-spring. Increased methane humidity at

4092-457: The clouds above the equatorial Xanadu region, suggestive of "methane drizzle", though this was not direct evidence for rain. However, subsequent images of lakes in Titan's southern hemisphere taken over one year show that they are enlarged and filled by seasonal hydrocarbon rainfall. It is possible that areas of Titan's surface may be coated in a layer of tholins , but this has not been confirmed. The presence of rain indicates that Titan may be

4185-399: The course of Saturn's 30-year orbit, Titan's cloud systems appear to manifest for 25 years, and then fade for four to five years before reappearing again. Cassini has also detected high-altitude, white, cirrus -type clouds in Titan's upper atmosphere, likely formed of methane. Although no evidence of lightning activity has yet been observed on Titan, computer models suggest that clouds in

4278-466: The dunes are 80–130 metres (260–430 ft) tall, with the dunes appearing dark in Cassini SAR imagery. Interactions between the dunes and obstacle features, such as mountains, indicate that sand is generally transported in a west-to-east direction. The sand that constructs the dunes is dominated by organic material, probably from Titan's atmosphere; possible sources of sand include river channels or

4371-399: The easternmost tip of a bright region now called Adiri . The probe photographed pale hills with dark "rivers" running down to a dark plain. Current understanding is that the hills (also referred to as highlands) are composed mainly of water ice. Dark organic compounds, created in the upper atmosphere by the ultraviolet radiation of the Sun, may rain from Titan's atmosphere. They are washed down

4464-449: The eccentricity of Saturn's orbit, Titan is about 12% closer to the Sun during the southern hemisphere summer, making southern summers shorter but hotter than northern summers. This asymmetry may contribute to topological differences between the hemispheres - the northern hemisphere has many more hydrocarbon lakes. Titan's lakes are largely placid, with few waves or ripples; however, Cassini has found evidence of increasing turbulence during

4557-405: The equilibrium that would be reached in the absence of any atmosphere]" Titan's orbital tilt with respect to the Sun is very close to Saturn's axial tilt (about 27°), and its axial tilt with respect to its orbit is zero. This means that the direction of incoming sunlight is driven almost entirely by Titan's day-night cycle and Saturn's year cycle. The day cycle on Titan lasts 15.9 Earth days, which

4650-670: The first observed moon orbiting Saturn with one of the telescopes they built. Huygens named his discovery Saturni Luna (or Luna Saturni , Latin for "moon of Saturn"), publishing in the 1655 tract De Saturni Luna Observatio Nova ( A New Observation of Saturn's Moon ). After Giovanni Domenico Cassini published his discoveries of four more moons of Saturn between 1673 and 1686, astronomers began referring to these and Titan as Saturn I through V (with Titan then in fourth position). Other early epithets for Titan include "Saturn's ordinary satellite." The International Astronomical Union officially numbers Titan as "Saturn VI." The name Titan , and

4743-460: The formation of hydrocarbon clouds and heavy organonitrogen haze . Its climate —including wind and rain—creates surface features similar to those of Earth , such as dunes, rivers, lakes, seas (probably of liquid methane and ethane), and deltas, and is dominated by seasonal weather patterns as on Earth. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan's methane cycle nearly resembles Earth's water cycle , albeit at

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4836-401: The greenhouse warming, and keeps the surface somewhat cooler than would otherwise be expected from the greenhouse effect alone. According to McKay et al., "the anti-greenhouse effect on Titan reduces the surface temperature by 9 K whereas the greenhouse effect increases it by 21 K. The net effect is that the surface temperature (94 K) is 12 K warmer than the effective temperature 82 K. [ i.e. ,

4929-486: The ground and by Cassini ; at least one of these, Ligeia Mare , Titan's second-largest sea, is almost a pure methane sea. Following the Voyager flybys, Titan was confirmed to have an atmosphere capable of supporting liquid hydrocarbons on its surface. However, the first tentative detection only came in 1995, when data from the Hubble Space Telescope and radar observations suggested expansive hydrocarbon lakes, seas, or oceans. The existence of liquid hydrocarbons on Titan

5022-438: The heat flux from within Titan itself, which is poorly constrained. The interior may still be hot enough for a liquid layer consisting of a " magma " composed of water and ammonia between the ice I h crust and deeper ice layers made of high-pressure forms of ice. The heat flow from inside Titan may even be too high for high pressure ices to form, with the outermost layers instead consisting primarily of liquid water underneath

5115-412: The highest-resolution images ever of Titan's surface, at only 1,200 kilometres (750 mi), discerning patches of light and dark that would be invisible to the human eye. On July 22, 2006, Cassini made its first targeted, close fly-by at 950 kilometres (590 mi) from Titan; the closest flyby was at 880 kilometres (550 mi) on June 21, 2010. Liquid has been found in abundance on the surface in

5208-420: The hills with the methane rain and are deposited on the plains over geological time scales. After landing, Huygens photographed a dark plain covered in small rocks and pebbles, which are composed of water ice. The two rocks just below the middle of the image on the right are smaller than they may appear: the left-hand one is 15 centimeters across, and the one in the center is 4 centimeters across, at

5301-485: The huge dunes of soot like material raining down from the atmosphere in the equatorial regions may instead be shaped by rare storm winds that happen only every fifteen years when Titan is in equinox . The storms produce strong downdrafts, flowing eastward at up to 10 meters per second when they reach the surface. In late 2010, the equivalent of early Spring in Titan's northern hemisphere, a series of methane storms were observed in Titan's equatorial desert regions. Due to

5394-416: The isotope up from the interior. Titan's surface has comparatively few impact craters, with erosion, tectonics, and cryovolcanism possibly working to erase them over time. Compared to the craters of similarly sized and structured Ganymede and Callisto, those of Titan are much shallower. Many have dark floors of sediment; geomorphological analysis of impact craters largely suggests that erosion and burial are

5487-430: The largest moon of Saturn , is similar in many respects to that of Earth , despite having a far lower surface temperature. Its thick atmosphere , methane rain, and possible cryovolcanism create an analogue, though with different materials, to the climatic changes undergone by Earth during the far shorter year of Earth. Titan receives just about 1% of the amount of sunlight Earth does. The average surface temperature

5580-512: The largest sea; Ligeia Mare, the second-largest sea; and Punga Mare, each filling broad depressions and cumulatively representing roughly 80% of Titan's sea and lake coverage—691,000 square kilometres (267,000 sq mi) combined. All three maria's sea levels are similar, suggesting that they may be hydraulically connected. The southern polar region, meanwhile, hosts four dry broad depressions, potentially representing dried-up seabeds. Additional smaller lakes occupy Titan's polar regions, covering

5673-405: The liquid–ice boundary of a subsurface ocean . Surface features were observed by the Cassini spacecraft to systematically shift by up to 30 kilometres (19 mi) between October 2005 and May 2007, which suggests that the crust is decoupled from the interior, and provides additional evidence for an interior liquid layer. Further supporting evidence for a liquid layer and ice shell decoupled from

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5766-507: The methane in its atmosphere may be its interior, released via eruptions from cryovolcanoes . On April 3, 2013, NASA reported that complex organic chemicals , collectively called tholins , likely arise on Titan, based on studies simulating the atmosphere of Titan. On June 6, 2013, scientists at the IAA-CSIC reported the detection of polycyclic aromatic hydrocarbons in the upper atmosphere of Titan. On September 30, 2013, propene

5859-450: The moon's lower troposphere can accumulate enough charge to generate lightning from an altitude of roughly 20 km. The presence of lightning in Titan's atmosphere would favour the production of organic materials. Cassini did not detect any lightning in Titan's atmosphere, though lightning could still be present if it was too weak to be detected. Recent computer simulations have shown that under certain circumstances streamer discharges ,

5952-570: The moon's thick atmosphere, it would appear 11.4 times larger in the sky, in diameter, than the Moon from Earth, which subtends 0.48° of arc. Titan is primarily composed of ice and rocky material, with a rocky core surrounded by various layers of ice, including a crust of ice I h and a subsurface layer of ammonia-rich liquid water. Much as with Venus before the Space Age , the dense opaque atmosphere prevented understanding of Titan's surface until

6045-558: The names of all seven satellites of Saturn then known, came from John Herschel (son of William Herschel , discoverer of two other Saturnian moons, Mimas and Enceladus ), in his 1847 publication Results of Astronomical Observations Made during the Years 1834, 5, 6, 7, 8, at the Cape of Good Hope . Numerous small moons have been discovered around Saturn since then. Saturnian moons are named after mythological giants. The name Titan comes from

6138-405: The north polar region, in the form of many lakes and seas discovered by Cassini . Huygens was an atmospheric probe that touched down on Titan on January 14, 2005, discovering that many of its surface features seem to have been formed by fluids at some point in the past. Titan is the most distant body from Earth to have a space probe land on its surface. The Huygens probe landed just off

6231-521: The northern hemisphere during the winter, decreased haze around the equinoxes due to changing atmospheric circulation, and associated ice clouds in the South Polar regions. The last equinox occurred on August 11, 2009; this was the spring equinox for the northern hemisphere, meaning the southern hemisphere is getting less sunlight and moving into winter. Surface winds are normally low (<1 meter per second). Recent computer simulations indicate that

6324-513: The northern hemisphere summer, suggesting that surface winds may strengthen during certain times of the Titanian year. Waves and ripples have also been seen by Cassini . The findings of the Huygens probe indicate that Titan's atmosphere periodically rains liquid methane and other organic compounds onto the moon's surface. In October 2007, observers noted an increase in apparent opacity in

6417-429: The northern hemisphere that resemble maar craters on Earth, which are created by explosive subterranean eruptions. The likeliest cryovolcano features is a complex of landforms that includes two mountains, Doom Mons and Erebor Mons ; a large depression, Sotra Patera ; and a system of flow-like features, Mohini Fluctus . Between 2005 and 2006, parts of Sotra Patera and Mohini Fluctus became significantly brighter whilst

6510-573: The northern hemisphere, where most of the lakes reside, enters the long Titanean summer, wind speeds might increase to 3 km/h, levels sufficient to produce waves. Waves have been observed on several occasions by Cassini RADAR and the Visual and Infrared Mapping Spectrometer since 2014, which were likely generated from summer winds or tidal currents. Simulations of global wind patterns based on wind speed data taken by Huygens during its descent have suggested that Titan's atmosphere circulates in

6603-442: The only Solar System body besides Earth upon which rainbows could form. However, given the extreme opacity of the atmosphere to visible light, the vast majority of any rainbows would be visible only in the infrared. The number of methane lakes visible near Titan's south pole is decidedly smaller than the number observed near the north pole. As the south pole is currently in summer and the north pole in winter, an emerging hypothesis

6696-436: The other, taking methane rainclouds with it. This means that Titan, despite its frigid temperatures, can be said to have a tropical climate. In June 2012, Cassini imaged a rotating polar vortex on Titan's southern pole, which the imaging team believe is related to a "polar hood"—an area of dense, high altitude haze seen over the northern pole since the probe's arrival in 2004. As the hemispheres are now switching seasons since

6789-417: The overall haze. The findings of the Huygens probe indicate that Titan's atmosphere periodically rains liquid methane and other organic compounds onto its surface. Clouds typically cover 1% of Titan's disk, though outburst events have been observed in which the cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during

6882-435: The primary mechanisms of crater modification. Titan's craters are also not evenly distributed, as the polar regions are almost devoid of any identified craters whilst the majority are located in the equatorial dune fields. This inequality may be the result of oceans that once occupied Titan's poles, polar sediment deposition by past rainfall, or increased rates of erosion in the polar regions. The majority of Titan's surface

6975-448: The similarly sized Ganymede, in the Jovian system. Observations of Titan prior to the space age were limited. In 1907 Spanish astronomer Josep Comas i Solà observed limb darkening of Titan, the first evidence that the body has an atmosphere. In 1944 Gerard P. Kuiper used a spectroscopic technique to detect an atmosphere of methane. The first probe to visit the Saturnian system was Pioneer 11 in 1979, which revealed that Titan

7068-571: The solid core comes from the way the gravity field varies as Titan orbits Saturn. Comparison of the gravity field with the RADAR-based topography observations also suggests that the ice shell may be substantially rigid. Titan is the only moon in the Solar System with an atmosphere denser than Earth's, with a surface pressure of 1.448 atm, and it is one of only two moons whose atmospheres are able to support clouds, hazes, and weather—the other being Neptune's moon Triton . The presence of

7161-498: The south pole possibly contributes to the rapid increases in cloud size. There had been summer in Titan's southern hemisphere until 2010, when Saturn's orbit, which governs the moon's motion, tilted the northern hemisphere towards the Sun. When the seasons switch, it is expected that ethane will begin to condense over the south pole. Research models that match well with observations suggest that clouds on Titan cluster at preferred coordinates and that cloud cover varies by distance from

7254-488: The southern summer generate uplift in the atmosphere, resulting in convection . This explanation is complicated by the fact that cloud formation has been observed not only after the southern summer solstice but also during mid-spring. Increased methane humidity at the south pole possibly contributes to the rapid increases in cloud size. It was summer in Titan's southern hemisphere until 2010, when Saturn's orbit, which governs Titan's motion, moved Titan's northern hemisphere into

7347-471: The stratosphere; simulations suggest it ought to change every twelve years, with a three-year transition period, over the course of Titan's year (30 terrestrial years). This cell creates a global band of low pressure—what is in effect a variation of Earth's Intertropical Convergence Zone (ITCZ). Unlike on Earth, however, where the oceans confine the ITCZ to the tropics, on Titan, the zone wanders from one pole to

7440-423: The sunlight. When the seasons switch, it is expected that ethane will begin to condense over the south pole. The surface of Titan has been described as "complex, fluid-processed, [and] geologically young". Titan has been around since the Solar System's formation, but its surface is much younger, between 100 million and 1 billion years old. Geological processes may have reshaped Titan's surface. Titan's atmosphere

7533-477: The surface in high-latitude regions. Hydrogen is the third-most abundant gas, with a concentration of around 0.1%. There are trace amounts of other hydrocarbons , such as ethane , diacetylene , methylacetylene , acetylene , and propane , and other gases, such as cyanoacetylene , hydrogen cyanide , carbon dioxide , carbon monoxide , cyanogen , argon , and helium . The hydrocarbons are thought to form in Titan's upper atmosphere in reactions resulting from

7626-576: The surface of Titan. NASA did not approve the requested $ 715 million, and the future of the project is uncertain. A conceptual design for another lake lander was proposed in late 2012 by the Spanish-based private engineering firm SENER and the Centro de Astrobiología in Madrid . The concept probe is called Titan Lake In-situ Sampling Propelled Explorer (TALISE). The major difference compared to

7719-472: The surface on different parts of the satellite. In the polar regions (above 60 degrees latitude ), widespread and permanent ethane clouds appear in and above the troposphere; at lower latitudes, mainly methane clouds are found between 15 and 18 km, and are more sporadic and localized. In the summer hemisphere, frequent, thick but sporadic methane clouds seem to cluster around 40°. Ground-based observations also reveal seasonal variations in cloud cover. Over

7812-585: The surface, about 90% has been absorbed by the thick atmosphere, leaving only 0.1% of the amount of light Earth receives. Atmospheric methane creates a greenhouse effect on Titan's surface, without which Titan would be much colder. Conversely, haze in Titan's atmosphere contributes to an anti-greenhouse effect by absorbing sunlight, canceling a portion of the greenhouse effect and making its surface significantly colder than its upper atmosphere. Titan's clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating

7905-522: The surface. There is also evidence that Titan's ice shell may be substantially rigid, which would suggest little geologic activity. There are also streaky features, some of them hundreds of kilometers in length, that appear to be caused by windblown particles. Examination has also shown the surface to be relatively smooth; the few features that seem to be impact craters appeared to have been partially filled in, perhaps by raining hydrocarbons or cryovolcanism. Radar altimetry suggests topographical variation

7998-495: The surrounding plains remained unchanged, potentially indicative of ongoing cryovolcanic activity. Indirect lines of evidence for cryovolcanism include the presence of Argon-40 in Titan's atmosphere. Radiogenic Ar is sourced from the decay of K , and has likely been produced within Titan over the course of billions of years within its rocky core. Ar's presence in Titan's atmosphere is thus supportive of active geology on Titan, with cryovolcanism being one possible method of bringing

8091-553: The tidal range of Titan's major seas are around 0.2–0.8 metres (0.66–2.62 ft). Through Cassini RADAR mapping of Titan's surface, numerous landforms have been interpreted as candidate cryovolcanic and tectonic features by multiple authors. A 2016 analysis of mountainous ridges on Titan revealed that ridges are concentrated in Titan's equatorial regions, implying that ridges either form more frequently in or are better preserved in low-latitude regions. The ridges—primarily oriented east to west—are linear to arcuate in shape, with

8184-471: The troposphere. Direct observations by the Huygens probe determined that methane concentrations are highest near the surface, with a concentration of 4.92% that remains relatively constant up to 8 kilometres (5.0 mi) above the surface. Methane concentrations then gradually decrease with increasing altitude, down to a concentration of 1.41% in the stratosphere. Methane also increases in concentration near Titan's winter pole, probably due to evaporation from

8277-483: Was detected in the atmosphere of Titan by NASA 's Cassini spacecraft, using its composite infrared spectrometer (CIRS). 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. The detection of propene fills a mysterious gap in observations that date back to NASA's Voyager 1 spacecraft's first close planetary flyby of Titan in 1980, during which it

8370-489: Was discovered that many of the gases that make up Titan's brown haze were hydrocarbons, theoretically formed via the recombination of radicals created by the Sun's ultraviolet photolysis of methane. Titan's surface temperature is about 94 K (−179.2 °C). At this temperature, water ice has an extremely low vapor pressure , so the little water vapor present appears limited to the stratosphere. Titan receives about 1% as much sunlight as Earth. Before sunlight reaches

8463-475: Was finally confirmed in situ by the Cassini orbiter, with the Cassini mission team announcing "definitive evidence of the presence of lakes filled with liquid methane on Saturn's moon Titan" in January 2007. The observed lakes and seas of Titan are largely restricted to its polar regions, where colder temperatures allow the presence of permanent liquid hydrocarbons. Near Titan's north pole are Kraken Mare,

8556-430: Was probably too cold to support life. It took images of Titan, including Titan and Saturn together in mid to late 1979. The quality was soon surpassed by the two Voyagers . Titan was examined by both Voyager 1 and 2 in 1980 and 1981, respectively. Voyager 1 's trajectory was designed to provide an optimized Titan flyby, during which the spacecraft was able to determine the density, composition, and temperature of

8649-576: Was selected for a Phase-A design study in 2011 as a candidate mission for the 12th NASA Discovery Program opportunity, but was not selected for flight. Another mission to Titan proposed in early 2012 by Jason Barnes, a scientist at the University of Idaho , is the Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR): an uncrewed plane (or drone ) that would fly through Titan's atmosphere and take high-definition images of

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