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Titan (or Saturn VI) is the largest moon of Saturn. It is the only natural satellite known to have a denseatmosphere,[8] and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found.[9]  SONY Vaio PCG-K33 Laptop Keyboard

Titan is the sixth ellipsoidal moon from Saturn. Frequently described as a planet-like moon, Titan has a diameter roughly 50% larger than the Moon and is 80% more massive. It is the second-largest moon in the Solar System, after Jupiter's moonGanymede, and is larger by volume than the smallest planet, Mercury, although only about 41% as massive.  DELL INSPIRON 1464 Laptop Keyboard

Titan was the first known moon of Saturn, discovered in 1655 by the Dutch astronomer Christiaan Huygens, and was the fifth moon (not including the Moon) to be discovered.[10]

Titan is primarily composed of water ice and rocky material. Much as with Venus prior to the Space Age, the dense, DELL XPS 15 L502X Laptop Keyboard

opaque atmosphere prevented understanding of Titan's surface until new information accumulated with the arrival of the Cassini–Huygens mission in 2004, including the discovery of liquid hydrocarbon lakes in Titan's polar regions. The surface is geologically young; although mountains and several possible cryovolcanoes have been discovered, it is smooth and fewimpact craters have been found.[11][12] DELL Vostro 1015 Laptop Keyboard

The atmosphere of Titan is largely composed of nitrogen; minor components lead to the formation of methane and ethaneclouds and nitrogen-rich organic smog. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes and seas (probably of liquid methane and ethane), and deltas, HP 643263-001 Laptop Keyboard

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 is viewed as an analog to Earth's water cycle, although at a much lower temperature.

Titan was discovered on March 25, 1655, by the Dutch astronomer/physicist Christiaan Huygens. SAMSUNG N140 Laptop Keyboard

Huygens was inspired by Galileo's discovery of Jupiter's four largest moons in 1610 and his improvements in telescope technology.[13] Christiaan, with the help of his brother Constantijn Huygens, Jr., began building telescopes around 1650. Christiaan Huygens discovered this first observed moon orbiting Saturn with the first telescope they built.[14] TOSHIBA Mini NB 505-SP0160 Laptop Keyboard

He named it simply Saturni Luna (or Luna Saturni, Latin for "Saturn's moon"), publishing in the 1655 tract De Saturni Luna Observatio Nova. After Giovanni Domenico Cassini published his discoveries of four more moons of Saturn between 1673 and 1686, astronomers fell into the habit of referring to these and Titan as Saturn I through V (with Titan then in fourth position). IBM 42T4026 laptop keyboard

Other early epithets for Titan include "Saturn's ordinary satellite".[15] Titan is officially numberedSaturn VI because after the 1789 discoveries the numbering scheme was frozen to avoid causing any more confusion (Titan having borne the numbers II and IV as well as VI). Numerous small moons have been discovered closer to Saturn since then. Lenovo 3000 G530 4151 laptop keyboard

The name Titan, and the names of all seven satellites of Saturn then known, came from John Herschel (son of William Herschel, discoverer of Mimas and Enceladus) in his 1847 publication Results of Astronomical Observations Made at the Cape of Good Hope.[16] He suggested the names of the mythological Titans (Greek: Τῑτάν), sisters and brothers of Cronus, the Greek Saturn. SONY VAIO VGN-N21E/W laptop keyboard

In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age.

Titan orbits Saturn once every 15 days and 22 hours. Like many of the other satellites of the gas giants and the Moon, its rotational period is identical to its orbital period; HP Pavilion DV7T-4100 laptop keyboard

Titan is thus tidally locked in synchronous rotation with Saturn, and always shows one face to the planet. Because of this, there is a sub-Saturnian point on its surface, from which the planet would appear to hang directly overhead. Longitudes on Titan are measured westward from the meridian passing through this point.[17] SONY VAIO VGN-FS215E laptop keyboard

 Its orbital eccentricity is 0.0288, and the orbital plane is inclined 0.348 degrees relative to the Saturnian equator.[1] Viewed from Earth, Titan reaches an angular distance of about 20 Saturn radii (just over 1.2 million km) from Saturn and subtends a disk 0.8 arcseconds in diameter.

The small, irregularly shaped satellite Hyperion is locked in a 3:4 orbital resonance with Titan. SONY Vaio PCG-K23 laptop keyboard

A "slow and smooth" evolution of the resonance—in which Hyperion would have migrated from a chaotic orbit—is considered unlikely, based on models. Hyperion probably formed in a stable orbital island, whereas the massive Titan absorbed or ejected bodies that made close approaches.

Titan is 5,150 km across, compared to 4,879 km for the planet Mercury, 3,474 km for the Moon, DELL NSK-DB301 laptop keyboard

and 12,742 km for the Earth. Before the arrival of Voyager 1 in 1980, Titan was thought to be slightly larger than Ganymede (diameter 5,262 km) and thus the largest moon in the Solar System; this was an overestimation caused by Titan's dense, opaque atmosphere, which extends many kilometres above its surface and increases its apparent diameter.[19] TOSHIBA P205-S7469 laptop keyboard

Titan's diameter and mass (and thus its density) are similar to those of the Jovian moons Ganymede and Callisto.[20] Based on its bulk density of 1.88 g/cm3, Titan's bulk composition is half water ice and half rocky material. Though similar in composition to Dione and Enceladus, it is denser due to gravitational compression. HP 6730S laptop keyboard

Titan is likely differentiated into several layers with a 3,400 km rocky center surrounded by several layers composed of different crystal forms of ice.[21] Its interior may still be hot and there may be a liquid layer consisting of a "magma" composed of water and ammonia between the ice Ih crust and deeper ice layers made of high-pressure forms of ice. SONY VAIO VGN-NW110D laptop keyboard

The presence of ammonia allows water to remain liquid even at temperatures as low as 176 K (−97 °C) (for eutectic mixture with water).[22] Evidence for such an ocean has recently been uncovered by theCassini probe in the form of natural extremely-low-frequency (ELF) radio waves in Titan's atmosphere. SONY VAIO VGN-N250E/B laptop keyboard

Titan's surface is thought to be a poor reflector of ELF waves, so they may instead be reflecting off the liquid–ice boundary of a subsurface ocean.[23] Surface features were observed by the Cassini spacecraft to systematically shift by up to 30 km 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.[24] HP G42-475TU laptop keyboard

An early 2000 study by the DLR Institute of Planetary Research at Berlin-Adlershof placed Titan in a "large icy satellite" group along with the Galilean moons Callisto and Ganymede.

The moons of Jupiter and Saturn are thought to have formed through co-accretion, a similar process to that believed to have formed the planets in the Solar System. HP G62-a25SI laptop keyboard

As the young gas giants formed, they were surrounded by discs of material that gradually coalesced into moons. However, whereas Jupiter possesses four large satellites in highly-regular, planet-like orbits, Titan overwhelmingly dominates Saturn's system and possesses a high orbital eccentricity not immediately explained by co-accretion alone. IBM Thinkpad R40 laptop keyboard

A proposed model for the formation of Titan is that Saturn's system began with a group of moons similar to Jupiter's Galilean satellites, 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 a violent beginning would also explain Titan's orbital eccentricity. HP Pavilion DV7-3186cl laptop keyboard

Titan is the only known moon with more than a trace of atmosphere. Its atmosphere is the only nitrogen-rich dense atmosphere in the Solar System aside from Earth's. Observations of the atmosphere, made in 2004 by Cassini, suggest that Titan is a "super rotator", like Venus, with an atmosphere that rotates much faster than its surface.[27] SONY VAIO VGN-N320E/W laptop keyboard

Observations from the Voyagerspace probes have shown that the Titanian atmosphere is denser than Earth's, with a surface pressure about 1.45 times that of Earth's. Titan's atmosphere is about 1.19 times as massive as Earth's overall,[28] or about 7.3 times more massive on a per surface area basis. Lenovo ThinkPad Edge E520 laptop keyboard

It supports opaque haze layers that block most visible light from the Sun and other sources and renders Titan's surface features obscure.[29] Titan's lower gravity means that its atmosphere is far more extended than Earth's.[30]The atmosphere of Titan is opaque at many wavelengths and a complete reflectance spectrum of the surface is impossible to acquire from orbit.[31] HP Pavilion dv6-2170eo laptop keyboard

It was not until the arrival of the Cassini–Huygens mission in 2004 that the first direct images of Titan's surface were obtained.[32]

The atmospheric composition in the stratosphere is 98.4% nitrogen with the remaining 1.6% composed mostly of methane (1.4%) and hydrogen (0.1–0.2%).[7]  TOSHIBA Satellite L655-S5153 laptop keyboard

There are trace amounts of other hydrocarbons, such as ethane, diacetylene, methylacetylene,acetylene and propane, and of other gases, such as cyanoacetylene, hydrogen cyanide, carbon dioxide, carbon monoxide,cyanogen, argon and helium.[6] The hydrocarbons are thought to form in Titan's upper atmosphere in reactions resulting from the breakup of methane by the Sun's ultraviolet light, HP Pavilion DV7-3067cl laptop keyboard

producing a thick orange smog.[33] Titan spends 95% of its time within Saturn's magnetosphere, which may help shield Titan from the solar wind.[34]

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. HP Pavilion DV7-3180us laptop keyboard

This suggests that methane must be somehow replenished by a reservoir on or within Titan itself.[35] The ultimate origin of the methane in Titan's atmosphere may be its interior, released via eruptions from cryovolcanoes.[36][37][38]

On April 3, 2013, NASA reported that complex organic chemicals could arise on Titan based on studies simulating the atmosphere of Titan.[39] SONY VAIO VGN-FW11S laptop keyboard

On June 6, 2013, scientists at the IAA-CSIC reported the detection of polycyclic aromatic hydrocarbons in the upper atmosphere of Titan.

Titan's surface temperature is about 94 K (−179.2 °C). At this temperature water ice has an extremely low vapor pressure, so the atmosphere is nearly free of water vapor. Titan receives just about 1% of the amount of sunlight that Earth gets.[41] HP Pavilion dv6-2170ee laptop keyboard

Atmospheric methane creates a greenhouse effect on Titan's surface, without which Titan would be far colder.[42] Conversely,haze in Titan's atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, cancelling a portion of the greenhouse effect warming and making its surface significantly colder than its upper atmosphere.[43] HP Pavilion DV6-1122us laptop keyboard

Titan's clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze.[19] The findings of the Huygens probe indicate that Titan's atmosphere periodically rains liquid methane and other organic compounds onto its surface.[44] SONY VAIO VGN-FS315M laptop keyboard

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 the Titanian summer generate uplift in the atmosphere, resulting in convection.  DELL PK130801B00 laptop keyboard

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 the south pole possibly contributes to the rapid increases in cloud size.[45] It was summer in Titan's southern hemisphere until 2010, TOSHIBA Satellite L655-S5163 laptop keyboard

when Saturn's orbit, which governs Titan's motion, moved Titan's northern hemisphere into the sunlight.[46] 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".[48] HP Pavilion dv5t-1200se CTO laptop keyboard

 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.[49] Titan's atmosphere is twice as thick as the Earth's, making it difficult for astronomical instruments to image its surface in the visible light spectrum.[50]  COMPAQ Presario C700 Laptop Keyboard

The Cassini spacecraft is using infrared instruments, radar altimetry and synthetic aperture radar(SAR) imaging to map portions of Titan during its close fly-bys of Titan. The first images revealed a diverse geology, with both rough and smooth areas. There are features that seem volcanic in origin, which probably disgorge water mixed with ammonia.  HP G72-b60US Laptop Keyboard

There are also streaky features, some of them hundreds of kilometers in length, that appear to be caused by windblown particles.[51][52] 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. HP 519265-001 Laptop Keyboard

Radar altimetry suggests height variation 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.[53]

Titan's surface is marked by broad regions of bright and dark terrain. COMPAQ Presario C700 Laptop Keyboard

These include Xanadu, a large, reflective equatorial area about the size of Australia. It was first identified in infrared images from 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.[54] It is criss-crossed in places by dark lineaments—sinuous topographical features resembling ridges or crevices. Lenovo Thinkpad T420 Laptop Keyboard

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.[55] There are dark areas of similar size elsewhere on Titan, observed from the ground and byCassiniTOSHIBA Satellite A305 Laptop Keyboard

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, Compaq Presario CQ57 Series Laptop Keyboard

either in disconnected pockets or on the scale of satellite-wide oceans, similar to water on Earth.[56]

The Cassini mission confirmed the former hypothesis, although not immediately. When the probe arrived in the Saturnian system in 2004, it was hoped that hydrocarbon lakes or oceans might be detectable by reflected sunlight from the surface of any liquid bodies,  Lenovo 39T7417 Laptop Keyboard

but no specular reflections were initially observed.[57] Near Titan's south pole, an enigmatic dark feature named Ontario Lacus was identified[58] (and later confirmed to be a lake).[11] A possible shoreline was also identified near the pole via radar imagery.[59] Following a flyby on July 22, 2006, in which the Cassini spacecraft's radar imaged the northern latitudes (that were then in winter), DELL Vostro 3450 Laptop Keyboard

a number of large, smooth (and thus dark to radar) patches were seen dotting the surface near the pole.[60] Based on the observations, scientists announced "definitive evidence of lakes filled with methane on Saturn's moon Titan" in January 2007.[9][61] The Cassini–Huygens team concluded that the imaged features are almost certainly the long-sought hydrocarbon lakes, HP Mini 210-1014TU Laptop Keyboard

the first stable bodies of surface liquid found outside of Earth. Some appear to have channels associated with liquid and lie in topographical depressions.[9] The liquid erosion features appear to be a very recent occurrence: channels in some regions have created surprisingly little erosion, suggesting erosion on Titan is extremely slow, HP Pavilion DV6-1002tx Laptop Keyboard

or some other recent phenomena may have wiped out older riverbeds and landforms.[49] Overall, the Cassini radar observations have shown that lakes cover only a few percent of the surface, making Titan much drier than Earth.[62]Although most of the lakes are concentrated near the poles (where the relative lack of sunlight prevents evaporation), HP 519265-001 Laptop Keyboard

a number of long-standing hydrocarbon lakes in the equatorial desert regions have also been discovered, including one near the Huygens landing site in the Shangri-La region, which is about half the size of Utah's Great Salt Lake. The equatorial lakes are probably "oases", i.e. the likely supplier is underground aquifers.[63] DELL Precision M4500 Laptop Keyboard

In June 2008, the Visual and Infrared Mapping Spectrometer on Cassini confirmed the presence of liquid ethane beyond doubt in Ontario Lacus.[64] On December 21, 2008, Cassini passed directly over Ontario Lacus and observed specular reflection in radar. The strength of the reflection saturated the probe's receiver, DELL PK130801B00 Laptop Keyboard

indicating that the lake level did not vary by more than 3 mm (implying either that surface winds were minimal, or the lake's hydrocarbon fluid is viscous).[65][66]

Specular reflections are indicative of a smooth, mirror-like surface, so the observation corroborated the inference of the presence of a large liquid body drawn from radar imaging. HP Pavilion DV6-1030us Laptop Keyboard

The observation was made soon after the north polar region emerged from 15 years of winter darkness.

On July 8, 2009, Cassini's VIMS observed a specular reflection indicative of a smooth, mirror-like surface, off what today is called Jingpo Lacus, a lake in the north polar region shortly after the area emerged from 15 years of winter darkness.[67][68] HP Probook 4520S Laptop Keyboard

Radar measurements made in July 2009 and January 2010 indicate that Ontario Lacus is extremely shallow, with an average depth of 0.4–3.2 m, and a maximum depth of 2.9–7.4 m.[69] In contrast, the northern hemisphere's Ligeia Mare has depths exceeding 8 m, the maximum measurable by the radar instrument.[69] SONY 147977821 Laptop Keyboard

During a flyby on 26 September 2012, Cassini's radar detected in Titan's northern polar region what is likely a river with a length of more than 400 kilometers. It has been compared with the much larger Nile river on Earth. This feature ends in Ligeia Mare.[11] SONY 147963021 Laptop Keyboard

During six flybys of Titan from 2006 to 2011, Cassini gathered radio-metric tracking and optical navigation data from which investigators could roughly infer Titan's changing shape. The density of Titan is consistent with a body that is about 60% rock and 40% water. The team's analyses suggest that Titan's surface can rise and fall by up to 10 metres during each orbit. SONY VAIO VGN-FS315M Laptop Keyboard

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.[70] The team's findings, together with the results of previous studies, hint that Titan's ocean may lie no more than 100 km below its surface. TOSHIBA Satellite C650-182 Laptop Keyboard

Radar, SAR and imaging data from Cassini have revealed few impact craters on Titan's surface.[49] These impacts appear to be relatively young, opposed to Titan's age.[49] The few impact craters discovered include a 440 km wide two-ring impact basin named Menrva seen by Cassini's ISS as a bright-dark concentric pattern.[73] ASUS F3M Laptop Keyboard

A smaller, 60 km wide, flat-floored crater named Sinlap[74] and a 30 km crater with a central peak and dark floor named Ksa have also been observed.[75] Radar and Cassiniimaging have also revealed a number of "crateriforms", circular features on the surface of Titan that may be impact related, but lack certain features that would make identification certain. Lenovo 63Y0047 Laptop Keyboard

For example, a 90 km wide ring of bright, rough material known as Guabonito has been observed by Cassini.[76] This feature is thought to be an impact crater filled in by dark, windblown sediment. Several other similar features have been observed in the dark Shangri-la and Aaru regions. Radar observed several circular features that may be craters in the bright region Xanadu during Cassini's April 30, 2006 flyby of Titan.[77]  HP Pavilion dv6-3107ax Laptop Keyboard

Many of Titan's craters or probable craters display evidence of extensive erosion, and all show some indication of modification.[72] Most large craters have breached or incomplete rims, despite the fact that some craters on Titan have relatively more massive rims than those anywhere else in the Solar System.HP 488590-001 Laptop Keyboard

However, there is little evidence of formation ofpalimpsests through viscoelastic crustal relaxation, unlike on other large icy moons.[72] Most craters lack central peaks and have smooth floors, possibly due to impact-generation or later eruption of cryovolcanic lava. Although infill from various geological processes is one reason for Titan's relative deficiency of craters, atmospheric shielding also plays a role; TOSHIBA P000482730 Laptop Keyboard

it is estimated that Titan's atmosphere reduces the number of craters on its surface by a factor of two.[78]

The limited high-resolution radar coverage of Titan obtained through 2007 (22%) suggested the existence of a number of nonuniformities in its crater distribution. Xanadu has 2–9 times more craters than elsewhere.  SONY 147977821 Laptop Keyboard

The leading hemisphere has a 30% higher density than the trailing hemisphere. There are lower crater densities in areas of equatorial dunes and in the north polar region (where hydrocarbon lakes and seas are most common).[72]

Pre-Cassini models of impact trajectories and angles suggest that where the impactor strikes the water ice crust, TOSHIBA Tecra M9-S5514 Laptop Keyboard

a small amount of ejecta remains as liquid water within the crater. It may persist as liquid for centuries or longer, sufficient for "the synthesis of simple precursor molecules to the origin of life".

Scientists have long speculated that conditions on Titan resemble those of early Earth, though at a much lower temperature.  GATEWAY NV-54 Laptop Keyboard

The detection of Argon 40 in the atmosphere in 2004 indicated that volcanoes had spawned plumes of "lava" composed of water and ammonia.[80] Global maps of the lake distribution on Titan's surface revealed that there is not enough surface methane to account for its continued presence in its atmosphere, and thus that a significant portion must be added through volcanic processes.[81] FUJITSU Lifebook P1510 Laptop Keyboard

Still there is a paucity of surface features that can be unambiguously interpreted as cryovolcanoes.[82] One of the first of such features revealed by Cassini radar observations in 2004, called Ganesa Macula, resembles the geographic features called "pancake domes" found on Venus, and was thus initially thought to be cryovolcanic in origin,  FUJITSU Lifebook P1610 Laptop Keyboard

although the American Geophysical Union refuted this hypothesis in December 2008. The feature was found to be not a dome at all, but appeared to result from accidental combination of light and dark patches.[83][84] In 2004 Cassini also detected an unusually bright feature (called Tortola Facula), which was interpreted as a cryovolcanic dome.[85]  DELL Precision M4500 Laptop Keyboard

No similar features have been identified as of 2010.[86] In December 2008, astronomers announced the discovery of two transient but unusually long-lived "bright spots" in Titan's atmosphere, which appear too persistent to be explained by mere weather patterns, suggesting they were the result of extended cryovolcanic episodes.[22]  SONY VAIO VGN-N325QE/W Laptop Keyboard

In March, 2009, structures resembling lava flows were announced in a region of Titan called Hotei Arcus, which appears to fluctuate in brightness over several months. Though many phenomena were suggested to explain this fluctuation, the lava flows were found to rise 200 meters above Titan's surface, consistent with it having been erupted from beneath the surface.[87]  TOSHIBA Satellite A205-S4618 Laptop Keyboard

A mountain range measuring 150 km long, 30 km wide and 1.5 km high was also discovered by Cassini in 2006. This range lies in the southern hemisphere and is thought to be composed of icy material and covered in methane snow. The movement of tectonic plates, perhaps influenced by a nearby impact basin, could have opened a gap through which the mountain's material upwelled.[88] HP G61-424CA laptop keyboard

 Prior to Cassini, scientists assumed that most of the topography on Titan would be impact structures, yet these findings reveal that similar to Earth, the mountains were formed through geological processes.[89] In December 2010, theCassini mission team announced the most compelling possible cryovolcano yet found.HP G61-424CA laptop keyboard

Named Sotra Patera, it is one in a chain of at least three mountains, each between 1000 and 1500 m in height, several of which are topped by large craters. The ground around their bases appears to be overlaid by frozen lava flows.[90]

If volcanism on Titan really exists, the hypothesis is that it is driven by energy released from the decay of radioactive elements within the mantle, as it is on the Earth.[22] Compaq Presario CQ56-102SE laptop keyboard

Magma on Earth is made of liquid rock, which is less dense than the solid rocky crust through which it erupts. Because ice is less dense than water, Titan's watery magma would be denser than its solid icy crust. This means that cryovolcanism on Titan would require a large amount of additional energy to operate, possibly via tidal flexing from nearby Saturn.[22] HP G42-265LA laptop keyboard

Alternatively, the pressure necessary to drive the cryovolcanoes may be caused by ice Ih "underplating" Titan's outer shell. The low-pressure ice, overlaying a liquid layer of ammonium sulfate, ascends buoyantly, and the unstable system can produce dramatic plume events. Titan is resurfaced through the process by grain-sized ice and ammonium sulfate ash, which helps produce a wind-shaped landscape and sand dune features.[91] TOSHIBA Satellite A305-S6841 laptop keyboard

In 2008 Jeffrey Moore (planetary geologist of Ames Research Center) proposed an alternate view of Titan's geology. Noting that no volcanic features had been unambiguously identified on Titan so far, he asserted that Titan is a geologically dead world, whose surface is shaped only by impact cratering, fluvial andeolian erosion, mass wasting and other exogenic processes. HP Mini 210-1081NR laptop keyboard

According to this hypothesis, methane is not emitted by volcanoes but slowly diffuses out of Titan's cold and stiff interior. Ganesa Macula may be an eroded impact crater with a dark dune in the center. The mountainous ridges observed in some regions can be explained as heavily degraded scarps of large multi-ring impact structures or as a result of the global contraction due to the slow cooling of the interior. HP G42-265LA laptop keyboard

Even in this case Titan may still have an internal ocean made of the eutectic water–ammonia mixture with the temperature of 176 K (−97 °C), which is low enough to be explained by the decay of radioactive elements in the core. The bright Xanadu terrain may be a degraded heavily cratered terrain similar to that observed on the surface of Callisto. TOSHIBA Satellite A305-S6829 laptop keyboard

Indeed, were it not for its lack of an atmosphere, Callisto could serve as a model for Titan's geology in this scenario. Jeffrey Moore even called Titan Callisto with weather.

In the first images of Titan's surface taken by Earth-based telescopes in the early 2000s, large regions of dark terrain were revealed straddling Titan's equator.[93] TOSHIBA PK13AT10600 laptop keyboard

 Prior to the arrival of Cassini, these regions were thought to be seas of organic matter like tar or liquid hydrocarbons.[94] Radar images captured by the Cassini spacecraft have instead revealed some of these regions to be extensive plains covered in longitudinal sand dunes, up to 330 meters high[95] about a kilometer wide, and tens to hundreds of kilometers long.COMPAQ Presario CQ50-210US laptop keyboard

The longitudinal (or linear) dunes are presumed to be formed by moderately variable winds that either follow one mean direction or alternate between two different directions. Dunes of this type are always aligned with average wind direction. In the case of Titan, steady zonal (eastward) winds combine with variable tidal winds (approximately 0.5 meters per second).[97] DELL V119525BS1 laptop keyboard

 The tidal winds are the result of tidal forces from Saturn on Titan's atmosphere, which are 400 times stronger than the tidal forces of the Moon on Earth and tend to drive wind toward the equator. This wind pattern causes sand dunes to build up in long parallel lines aligned west-to-east. The dunes break up around mountains, where the wind direction shifts.  TOSHIBA 9J.N9282.W01 laptop keyboard

The sand on Titan is likely not made up of small grains of silicates like the sand on Earth,[98] but rather might have formed when liquid methane rained and eroded the ice bedrock, possibly in the form of flash floods. Alternatively, the sand could also have come from organic solids produced by photochemical reactions in Titan's atmosphere.[ SONY KFRMBA151B laptop keyboard

Studies of dunes' composition in May 2008 revealed that they possessed less water than the rest of Titan, and are most likely to derive from organic material clumping together after raining onto the surface.

Titan is never visible to the naked eye, but can be observed through small telescopes or strong binoculars. TOSHIBA Satellite l25-s1196 laptop keyboard

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.[101] Titan has a maximumapparent magnitude of +8.2,[5] and mean opposition magnitude 8.4.[102]  HP Pavilion DV6-1205ee laptop keyboard

This compares to +4.6[102] for the similarly sized Ganymede, in the Jovian system.

Observations of Titan prior to the space age were limited. In 1907 Spanish astronomer Josep Comas Solá observed limb darkeningof 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.[103] SAMSUNG Q320 laptop keyboard

The first probe to visit the Saturnian system was Pioneer 11 in 1979, which confirmed that Titan was probably too cold to support life.[104] It took images of Titan, including Titan and Saturn together in mid to late 1979.[105] The quality was soon surpassed by the two Voyagers, but Pioneer 11 provided data for everyone to prepare with. TOSHIBA Satellite M645-S4070 Laptop Keyboard

Titan was examined by both Voyager 1 and 2 in 1980 and 1981, respectively. Voyager 1's course was diverted specifically to make a closer pass of Titan. Unfortunately, the craft did not possess any instruments that could penetrate Titan's haze, an unforeseen factor. Many years later,  HP Probook 4515S Laptop Keyboard

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,[106] but by then they had already been observed in the infrared by the Hubble Space Telescope. Voyager 2 took only a cursory look at Titan. SONY VAIO VGN-AR630E Laptop Keyboard

The Voyager 2 team had the option of steering the spacecraft to take a detailed look at Titan or to use another trajectory that would allow it to visit Uranus and Neptune. Given the lack of surface features seen by Voyager 1, the latter plan was implemented.

Even with the data provided by the VoyagersSONY VAIO PCG-FR315M Laptop Keyboard

Titan remained a body of mystery—a planet-like satellite shrouded in an atmosphere that makes detailed observation difficult. The intrigue that had surrounded Titan since the 17th-century observations of Christiaan Huygens and Giovanni Cassini was gratified by a spacecraft named in their honor. DELL Latitude D620 Laptop Keyboard

The Cassini–Huygens spacecraft reached Saturn on July 1, 2004, and has begun the process of mapping Titan's surface by radar. A joint project of the European Space Agency (ESA) and NASA, Cassini–Huygens has proved a very successful mission. The Cassini probe flew by Titan on October 26, 2004, and took the highest-resolution images ever of Titan's surface, DELL Latitude D620 Laptop Keyboard

at only 1,200 km, discerning patches of light and dark that would be invisible to the human eye from the Earth. Huygens landed[107] on Titan on January 14, 2005, discovering that many of its surface features seem to have been formed by flowing fluids at some point in the past.[108] On July 22, 2006, Cassinimade its first targeted, SAMSUNG N150 Laptop Keyboard

close fly-by at 950 km from Titan; the closest flyby was at 880 km on June 21, 2010.[109] Present liquid on the surface has been found in abundance in the north polar region, in the form of many lakes and seas discovered by Cassini.[60]Titan is the most distant body from Earth[110] and the second moon in the Solar System to have a space probe land on its surface. HP Pavilion G6-1B59WM Laptop Keyboard

On January 14, 2005, the Huygens probe landed on the surface of Titan, just off 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. HP G62-367DX Laptop Keyboard

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 the hills with the methane rain and are deposited on the plains over geological time scales.[111]

After landing, Huygens photographed a dark plain covered in small rocks and pebbles, which are composed of water ice.[111DELL V119525BS1 Laptop Keyboard

 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 a distance of about 85 centimeters from Huygens. There is evidence of erosion at the base of the rocks, indicating possible fluvial activity. SONY VAIO VGN-N250E/B laptop keyboard

The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. The assumption is that the "soil" visible in the images is precipitation from the hydrocarbon haze above.

In March 2007, NASA, ESA, and COSPAR decided to name the Huygens landing site the Hubert Curien Memorial Stationin memory of the former president of the ESA. HP Pavilion DV7-3067nr laptop keyboard

The Titan Saturn System Mission (TSSM) is a joint NASA/ESA proposal for exploration of Saturn's moons.[113] It envisions a hot-air balloon floating in Titan's atmosphere for six months. It was competing against the Europa Jupiter System Mission (EJSM) proposal for funding. SONY Vaio PCG-K315S laptop keyboard

In February 2009 it was announced that ESA/NASA had given the EJSM mission priority ahead of the TSSM,[114] although TSSM was still considered for a later launch date. Since NASA's departure from the program in 2012, these plans were put on hold.

There has also been a proposal for a Titan Mare Explorer (TiME), TOSHIBA Satellite L755-S5216 laptop keyboard

which would be a low-cost lander that would splash down in a lake near Titan's north pole and float on the surface of the lake for 3 to 6 months. It could launch as early as 2016 and arrive in 2023.[115][116][117] In 2012, however, NASA chose to fund the Mars probe InSight instead of TiME, rendering the Titan probe's future uncertain.  HP Pavilion DV6z artist edition 2 laptop keyboard

Another lake lander project was proposed in late 2012 in Europe. The concept probe is called Titan Lake In-situ Sampling Propelled Explorer (TALISE).[118][119] The major difference with the TiME probe would be a propulsion system.

Another proposed mission to Titan is the Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR),  HP Pavilion dv6-3142se laptop keyboard

which is an unmanned plane (or drone) which would fly through Titan's atmosphere and take high-definition images of the surface of Titan.

Titan is thought to be a prebiotic environment rich in complex organic chemistry[39] with a possible subsurface liquid ocean serving as a biotic environment. TOSHIBA Satellite P300-ST3712 laptop keyboard

Although the Cassini–Huygens mission was not equipped to provide evidence for biosignatures or complex organic compounds, it showed an environment on Titan that is similar, in some ways, to ones theorized for the primordial Earth.[126] Scientists surmise that the atmosphere of early Earth was similar in composition to the current atmosphere on Titan, with the important exception of a lack of water vapor on Titan. HP G42-265LA laptop keyboard

The Miller–Urey experiment and several following experiments have shown that with an atmosphere similar to that of Titan and the addition of UV radiation, complex molecules and polymer substances like tholins can be generated. The reaction starts with dissociation of nitrogen and methane, forming hydrogen cyanide and acetylene. Further reactions have been studied extensively.[128] SONY VAIO VGN-FS620 laptop keyboard

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