Titan

Titan seen from the Cassini–Huygens spacecraft. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its
Discovery
Discovered by	Christiaan Huygens
Discovery date	March 25, 1655
Orbital characteristics[1]
Semi-major axis	1,221,870 km
Eccentricity	0. Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch Events 1199 - Richard I is wounded by a crossbow bolt while fighting France which leads to his death on April 6. In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star In Geometry, the semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand In Astrodynamics, under standard assumptions, any Orbit must be of Conic section shape 0288
Orbital period	15. The orbital period is the time taken for a given object to make one complete Orbit about another object 945 days
Inclination	0. Inclination in general is the Angle between a Reference plane and another plane or axis of direction 34854° (to Saturn's equator)
Satellite of	Saturn
Physical characteristics
Mean radius	2576 ± 2. A natural satellite or moon is a Celestial body that Orbits a Planet or smaller body which is called the primary. 00 km (0. 404 Earths) [2]
Surface area	8. Equation A spheroid centered at the origin and rotated about the z axis is defined by the implicit equation \left(\frac{x}{a}\right^2+\left(\frac{y}{a}\right^2+\left(\frac{z}{b}\right^2 3×107 km²
Mass	1. Square Kilometre ( US spelling square kilometer) symbol km2, is a decimal multiple of the SI unit of Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object 3452 ± 0. 0002×1023 kg (0. 0225 Earths)[2]
Mean density	1. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 8798 ± 0. 0044 g/cm³[2]
Equatorial surface gravity	1. For other uses of the words gram or gramme see Gram (disambiguation. A cubic centimetre or cubic centimeter (symbol cm3 —the abbreviation cc, though widely used is deprecated is a commonly used unit of Volume The surface gravity, g, of an astronomical or other object is the Gravitational acceleration experienced at its surface 352 m/s2 (0. 14 g)
Escape velocity	2. g-force (also G-force, g-load) is a measurement of an object's Acceleration expressed in g s In Physics, escape velocity is the speed where the Kinetic energy of an object is equal to the magnitude of its Gravitational potential energy 639 km/s
Rotation period	(synchronous)
Axial tilt	zero
Albedo	0. The rotation period of an astronomical object is the time it takes to complete one revolution around its Axis of rotation relative to the background stars In Astronomy, synchronous rotation is a planetological term describing a body orbiting another where the orbiting body takes as long to rotate In Astronomy, axial tilt is the Inclination angle of a planet's rotational axis in relation to its orbital plane. The albedo of an object is the extent to which it diffusely reflects light from the sun 22[3]
Temperature	93. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature 7 K (−179. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic 45 °C)[4]
Apparent magnitude	7. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 9
Adjectives	Titanian
Atmosphere
Surface pressure	146. 7 kPa
Composition	98. 4% nitrogen 1. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 6% methane[5]

Christiaan Huygens, discoverer of Titan

Titan (pronounced /ˈtaɪtən/ TYE-tən, or as Greek: Τῑτάν) or Saturn VI is the largest moon of Saturn, the only moon known to have a dense atmosphere,^[6] and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly A natural satellite or moon is a Celestial body that Orbits a Planet or smaller body which is called the primary. An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " ^[7]

Titan is the twentieth most distant moon of Saturn and sixth farthest among those large enough to assume a spheroid shape. Equation A spheroid centered at the origin and rotated about the z axis is defined by the implicit equation \left(\frac{x}{a}\right^2+\left(\frac{y}{a}\right^2+\left(\frac{z}{b}\right^2 Frequently described as a satellite with planet-like characteristics, Titan has a diameter roughly 50% larger than Earth's moon and is 80% more massive. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object It is the second-largest moon in the Solar System, after Jupiter's moon Ganymede, and it is larger by diameter than the smallest planet, Mercury (although only half as massive). The tables below of Natural satellites in the Solar System are ordered from largest to smallest by average diameter The Solar System consists of the Sun and those celestial objects bound to it by Gravity. TemplateInfobox Planet.--> Ganymede (ˈgænɨmiːd, or as Greek Titan was the first known moon of Saturn, discovered in 1655 by the Dutch astronomer Christiaan Huygens. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch ^[8]

Titan is primarily composed of water ice and rocky material. The dense 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 the satellite's polar regions. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. These are the only large, stable bodies of surface liquid known to exist anywhere other than Earth. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The surface is geologically young; although mountains and several possible cryovolcanoes have been discovered, it is relatively smooth and few impact craters have been discovered. A cryovolcano is literally an Icy Volcano. Cryovolcanoes form on Icy moons and possibly on other low- Temperature Astronomical objects In the broadest sense the term impact crater can be applied to any depression natural or manmade resulting from the high velocity impact of a projectile with larger body

The atmosphere of Titan is largely composed of nitrogen and its climate includes methane and ethane clouds. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where The climate—including wind and rain—creates surface features that are similar to those on Earth, such as sand dunes and shorelines, and, like Earth, is dominated by seasonal weather patterns. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan is viewed as analogous to the early Earth, although at a much lower temperature. The satellite has thus been cited as a possible host for microbial extraterrestrial life or, at least, as a prebiotic environment rich in complex organic chemistry. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Extraterrestrial life is Life originating outside of the Earth. Researchers have suggested a possible underground liquid ocean might serve as a biotic environment. ^[9][10]

Discovery and naming

Titan was discovered on March 25, 1655, by the Dutch astronomer Christiaan Huygens. Events 1199 - Richard I is wounded by a crossbow bolt while fighting France which leads to his death on April 6. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch Huygens was inspired by Galileo's discovery of Jupiter's four largest moons in 1610 and his improvements on telescope technology. Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher The Galilean moons are the four moons of Jupiter discovered by Galileo Galilei. A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. ^[11] Huygens himself made advances in the technology and his discovery of Titan owed "partly to the quality of his telescope and partly to luck". ^[12] 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). Giovanni Domenico Cassini ( June 8, 1625 &ndash September 14, 1712) was an Italian Mathematician, Astronomer Other early epithets for Titan include "Saturn's ordinary satellite". ^[13] Titan is officially numbered Saturn 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.

The name Titan, and the names of all seven satellites of Saturn then known, come 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. Sir John Frederick William Herschel 1st Baronet KH, FRS ( March 7, 1792 &ndash May 11, 1871)was an Sir Frederick William Herschel FRS KH ( 15 November 1738 – 25 August 1822) was a German -born British ^[14] He suggested the names of the mythological Titans, sisters and brothers of Cronos, the Greek Saturn. In Greek mythology, the Titans ( Greek: Tītā́n; plural Tītânes) were a race of powerful Deities that ruled during the legendary Cronus or Kronos, ( Ancient Greek Κρόνος Krónos) was the leader and the youngest of the first generation of Titans, divine descendants

Orbit and rotation

Titan's orbit (highlighted in red) among the other large inner moons of Saturn. The moons outside its orbit are (l-r) Iapetus and Hyperion; those inside are Dione, Tethys, Enceladus and Mimas

Titan orbits Saturn once every 15 days and 22 hours. Like the Earth's moon and many of the other gas giant satellites, its orbital period is identical to its rotational period; Titan is thus tidally locked in synchronous rotation with Saturn. A separate article treats the phenomenon of Tidal resonance in Oceanography. In Astronomy, synchronous rotation is a planetological term describing a body orbiting another where the orbiting body takes as long to rotate Its orbital eccentricity is 0. 0288, and it is inclined 0. 348 degree relative to the Saturnian equator. ^[1] Viewed from Earth, the moon reaches an angular distance of about 20 Saturn radii (just over 1. 2 million kilometers) from Saturn and subtends a disk 0. 8 arcseconds in diameter. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree.

Titan is locked in a 3:4 orbital resonance with the small, irregularly shaped satellite Hyperion. In Celestial mechanics, an orbital resonance occurs when two Orbiting bodies exert a regular periodic gravitational influence on each other usually due to their TemplateInfobox Planet.--> Hyperion (haɪˈpɪəriən, or as in 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 likely formed in a stable orbital island, while massive Titan absorbed or ejected bodies that made close approaches. ^[15]

Bulk characteristics

Titan compared to Earth.

Titan's internal structure.

Titan is 5,150 km across, compared to 4,879 km for the planet Mercury and 3,474 km for Earth's moon. 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 miles above its surface and increases its apparent diameter. The Voyager 1 spacecraft is a 722-kilogram robotic Space probe of the outer Solar system and beyond launched September 5, ^[16] Titan's diameter and mass (and thus its density) are similar to Jovian moons Ganymede and Callisto. TemplateInfobox Planet.--> Ganymede (ˈgænɨmiːd, or as Greek TemplateInfobox Planet.--> Callisto (kəˈlɪstoʊ, or as Greek ^[17] 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. TemplateInfobox Planet.--> Dione (daɪˈoʊni, or as in Greek TemplateInfobox Planet.--> This article is about the moon of Gravitational compression is a process whereby Gravity acting on the Mass of an object compresses it increasing its Density and reducing its Volume

Titan is probably differentiated into several layers with a 3,400 km rocky center surrounded by several layers composed of different crystal forms of ice. ^[18] Its interior may still be hot and there may be a liquid layer consisting of water and ammonia between the ice I crust and deeper ice layers made of high-pressure forms of ice. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Ice Ih is the hexagonal crystal form of ordinary Ice, or frozen water. Evidence for such an ocean has recently been uncovered by the Cassini probe in the form of natural extremely low frequency (ELF) radio waves in Titan's atmosphere. Extremely low frequency (ELF is the band of Radio frequencies from 3 to 30 Hz. 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. ^[19] 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. ^[20]

Atmosphere

True-color image of layers of haze in Titan's atmosphere.

Titan is the only known moon with a fully developed atmosphere that consists of more than just trace gases. An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " The term Trace gas refers to a gas or gases which make up less than 1% by volume of the Earth's atmosphere, and therefore includes all gases except Nitrogen (78 Atmosphere thickness has been suggested ranging between 200 km^[21] and 880 km. ^[22] Compare these figures to Earth's boundary, which lies at 100 km, with 99. 999% of atmospheric mass lying below that altitude. [1] The atmosphere of Titan is opaque at many wavelengths and a complete reflectance spectrum of the surface is impossible to acquire from the outside;^[23] it was this haziness that led to errors in diameter estimates. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency.

The presence of a significant atmosphere was first discovered by Gerard P. Kuiper in 1944 using a spectroscopic technique that yielded an estimate of an atmospheric partial pressure of methane of the order of 100 millibars (10 kPa). Gerard Peter Kuiper ( born Gerrit Pieter Kuiper ( ( December 7 1905, Harenkarspel ( Tuitjenhorn) Netherlands &ndash Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ In a mixture of Ideal gases each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ^[24] Observations from the Voyager space probes have shown that the Titanian atmosphere is denser than Earth's, with a surface pressure more than one and a half times that of our planet. See also Voyager 1 and Voyager 2. The Voyager program consists of a pair of unmanned scientific probes Voyager 1 and EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 It supports opaque haze layers that block most visible light from the Sun and other sources and renders Titan's surface features obscure. The atmosphere is so thick and the gravity so low that humans could fly through it by flapping "wings" attached to their arms. ^[25] The Huygens probe was unable to detect the direction of the Sun during its descent, and although it was able to take images from the surface, the Huygens team likened the process to "taking pictures of an asphalt parking lot at dusk". The Huygens probe, supplied by the European Space Agency (ESA and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry ^[26]

The atmosphere is 98. 4% nitrogen—the only dense, nitrogen-rich atmosphere in the solar system aside from the Earth's—with the remaining 1. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 6% composed of methane and trace amounts of other gases such as hydrocarbons (including ethane, diacetylene, methylacetylene, acetylene, propane, cyanoacetylene, hydrogen cyanide), carbon dioxide, carbon monoxide, cyanogen, argon and helium. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Diacetylene (also known as butadiyne) with the formula C4H2 is a highly unsaturated Hydrocarbon that contains one Single bond Methylacetylene ( propyne) is an Alkyne with the Chemical formula H 3C≡CH Acetylene ( IUPAC name ethyne), C2H2 is a Hydrocarbon belonging to the group of Alkynes It is the simplest of all alkynes Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable The polyynes are a group of Organic compounds with alternating single and triple bonds, for example buta-13-diyne ( Diacetylene) C4H2 Hydrogen cyanide is a Chemical compound with Chemical formula HCN Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Cyanogen is the Chemical compound with the formula ( C[[nitrogen N]]2 This article pertains to the chemical element For other uses see Argon (disambiguation. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical ^[5] The orange color as seen from space must be produced by other more complex chemicals in small quantities, possibly tholins, tar-like organic precipitates. Tholin (after the Greek word for muddy is a Heteropolymer formed by solar Ultraviolet irradiation of simple Organic compounds such as Methane ^[27] 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, producing a thick orange smog. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Titan has no magnetic field and sometimes orbits outside Saturn's magnetosphere, directly exposing it to the solar wind. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. This may ionize and carry away some molecules from the top of the atmosphere. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge In November 2007, scientists uncovered evidence of negative ions with roughly 10,000 times the mass of hydrogen in Titan's ionosphere, which are believed to fall into the lower regions to form the orange haze which obscures Titan's surface. Their structure is not currently known, but they are believed to be tholins, and may form the basis for the formation of more complex molecules, such as polycyclic aromatic hydrocarbons. Polycyclic aromatic hydrocarbons ( PAH s are Chemical compounds that consist of fused Aromatic rings and do not contain Heteroatoms or ^[28]

Energy from the Sun should have converted all traces of methane in Titan's atmosphere into hydrocarbons within 50 million years; a relatively short time compared to the age of the Solar System. This suggests that methane must be somehow replenished by a reservoir on or within Titan itself. That Titan's atmosphere contains over a thousand times more methane than carbon monoxide would appear to rule out significant contributions from cometary impacts, since comets are composed of more carbon monoxide than methane. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. That Titan might have accreted an atmosphere from the early Saturnian nebula at the time of formation also seems unlikely; in such a case, it ought to have atmospheric abundances similar to the solar nebula, including hydrogen and neon. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 ^[29] A possible biological origin for the methane has not been discounted (see below). ^[10]

There is also a pattern of air circulation found flowing in the direction of Titan's rotation, from west to east. ^[30] Observations by Cassini of the atmosphere made in 2004 also suggest that Titan is a "super rotator", like Venus, with an atmosphere that rotates much faster than its surface. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University ^[31]

Titan's ionosphere is also more complex than Earth's, with the main ionosphere at an altitude of 1,200 km but with an additional layer of charged particles at 63 km. This splits Titan's atmosphere to some extent into two separate radio-resonating chambers. The source of natural ELF waves (see above) on Titan is unclear as there does not appear to be extensive lightning activity. ^[19]

Surface features

See also: List of geological features on Titan

Titan in false color showing surface details and atmosphere. This is a list of named geological features on Saturn 's moon Titan. "Xanadu" is the bright region at the centre-right

A composite image of Titan's surface.

The surface of Titan has been described as "complex, fluid-processed, [and] geologically young". ^[32] The Cassini spacecraft has used radar altimetry and synthetic aperture radar (SAR) imaging to map portions of Titan during its close fly-bys of the moon. Synthetic-aperture radar (SAR is a form of Radar in which the highly-directional (and thus very large rotating antenna used by conventional radar is replaced with many low-directivity 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. A cryovolcano is literally an Icy Volcano. Cryovolcanoes form on Icy moons and possibly on other low- Temperature Astronomical objects There are also streaky features, some of them hundreds of kilometers in length, that appear to be caused by windblown particles. ^[33][34] 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. In the broadest sense the term impact crater can be applied to any depression natural or manmade resulting from the high velocity impact of a projectile with larger body 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. ^[35]

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. Xanadu (often called "Xanadu Regio" though this is not its official name is a highly reflective area on Reflection is the change in direction of a Wave front at an interface between two different media so that the wave front returns into the medium from which For a topic outline on this subject see List of basic Australia topics. It was first identified in infrared images from the Hubble Space Telescope in 1994, and later viewed by the Cassini spacecraft. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into The convoluted region is filled with hills and cut by valleys and chasms. ^[36] 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. This article discusses the geologic usage for the philosophical or architectural usage see Architectonics ' Or see Plate tectonics. Alternatively, the lineaments may be liquid-formed channels, suggesting old terrain that has been cut through by stream systems. ^[37] There are dark areas of similar size elsewhere on the moon, observed from the ground and by Cassini; it had been speculated that these are methane or ethane seas, but Cassini observations seem to indicate otherwise (see below).

Liquids

Main article: Lakes of Titan

False-color Cassini synthetic-aperture radar mosaic of Titan's north polar region, showing evidence for hydrocarbon seas, lakes and tributary networks. The lakes of Titan, a moon of Saturn, are bodies of liquid methane that have been detected by the Cassini space probe and had been suspected long The false blue coloring indicates low radar reflectivity areas, likely caused by bodies of liquid ethane, methane and dissolved nitrogen. Photographs suggest that the large body at lower left has about twice the extent visible here.

The possibility that there were seas of liquid methane on Titan were 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 wasn't obtained until 1995 when data from Hubble and other observations had already 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. The Voyager 1 spacecraft is a 722-kilogram robotic Space probe of the outer Solar system and beyond launched September 5, Voyager 2 is an unmanned Interplanetary Spacecraft launched on August 20, 1977. ^[38]

The Cassini mission affirmed 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, but no specular reflections were initially observed. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Specular reflection is the perfect Mirror -like reflection of light (or sometimes other kinds of Wave) from a surface in which light from a single incoming ^[39] At Titan's south pole, an enigmatic dark feature named Ontario Lacus was the first suspected lake identified, possibly created by clouds that are observed to cluster in the area. Ontario Lacus is a methane-ethane Lake near the south pole of Saturn 's moon Titan. ^[40] A possible shoreline was also identified at the pole via radar imagery. ^[41] Following a flyby on July 22, 2006, in which the Cassini spacecraft's radar imaged the northern latitudes (which are currently in winter), a number of large, smooth (and thus dark to radar) patches were seen dotting the surface near the pole. Events 1099 - First Crusade: Godfrey of Bouillon is elected the first Defender of the Holy Sepulchre of The Kingdom of Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. ^[42] Based on the observations, scientists announced "definitive evidence of lakes filled with methane on Saturn's moon Titan" in January 2007. ^[7][43] The Cassini–Huygens team concluded that the imaged features are almost certainly the long-sought hydrocarbon lakes, the first stable bodies of surface liquid found off Earth. Some appear to have channels associated with liquid and lie in topographical depressions. ^[7]

Impact craters

Impact crater on Titan's surface

Radar, SAR and imaging data from Cassini have revealed a relative paucity of impact craters on Titan's surface, suggesting a youthful surface. The few impact craters discovered include a 440 km wide multi-ring impact basin named Menrva (seen by Cassini's ISS as a bright-dark concentric pattern). ^[44] A smaller 80 km wide, flat-floored crater named Sinlap^[45] and a 30 km crater with a central peak and dark floor named Ksa have also been observed. ^[46] Radar and Cassini imaging 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. For example, a 90 km wide ring of bright, rough material known as Guabonito has been observed by Cassini. ^[47] 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. Events 313 - Roman emperor Licinius unifies the entire Eastern Roman Empire under his rule Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. ^[48]

Pre-Cassini models of impact trajectories and angles suggest that where the impactor strikes the water ice crust, 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". ^[49] While infill from various geological processes is one reason for Titan's relative deficiency of craters, atmospheric shielding also plays a role; it is estimated that Titan's atmosphere reduces the number of craters on its surface by a factor of two. ^[50]

Cryovolcanism and mountains

See also: Cryovolcano

Near-infrared image of Tortola Facula, thought to be a possible cryovolcano. A cryovolcano is literally an Icy Volcano. Cryovolcanoes form on Icy moons and possibly on other low- Temperature Astronomical objects

Scientists have speculated that conditions on Titan resemble those of early Earth, though at a much lower temperature. Evidence of volcanic activity from the latest Cassini mission suggests that temperatures are probably much higher in hotbeds, enough for liquid water to exist. Argon 40 detection in the atmosphere indicates that volcanoes spew plumes of "lava" composed of water and ammonia. This article pertains to the chemical element For other uses see Argon (disambiguation. ^[51] Cassini detected methane emissions from one suspected cryovolcano, and volcanism is now believed to be a significant source of the methane in the atmosphere. ^[52][53] One of the first features imaged by Cassini, Ganesa Macula, resembles the geographic features called "pancake domes" found on Venus, and is thus believed to be cryovolcanic in origin. Ganesa Macula is a dark feature on Saturn 's moon Titan. It is named after the Hindu god Ganesha. A pancake dome is an unusual type of Volcano found on the planet Venus. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University ^[54]

The pressure necessary to drive the cryovolcanoes may be caused by ice "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. Ammonium sulfate, (NH42SO4 is an inorganic chemical compound commonly used as a fertilizer 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. Aeolian (or Eolian or Æolian) processes pertain to the activity of the Winds and more specifically to the winds' ability to shape the surface of the ^[55]

A mountain range measuring 150 km long, 30 km wide and 1. 5 km high was 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. ^[56]

Dark terrain

Sand dunes on Earth (top), compared with dunes on Titan's surface.

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. ^[57] Prior to the arrival of Cassini, these regions were thought to be seas of organic matter like tar or liquid hydrocarbons. ^[58] 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. In physical Geography, a dune is a Hill of Sand built by Aeolian processes. ^[59] The longitudinal (or linear) dunes are believed 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. The terms zonal and meridional are used to describe directions on a Globe. 5 meter per second). ^[60] 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. The tidal force is a secondary effect of the Force of Gravity and is responsible for the Tides It arises because the gravitational acceleration experienced 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.

The sand on Titan 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. ^[61][59][60] 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. ^[62]

Climate

A graph detailing temperature, pressure, and other aspects of Titan's climate. The atmospheric haze lowers the temperature in the lower atmosphere, while methane raises the temperature at the surface. Cryovolcanoes erupt methane into the atmosphere, which then rains down onto the surface, forming lakes.

Titan's surface temperature is about 94 K (−179 °C, or −290 °F). At this temperature water ice does not sublimate or evaporate, so the atmosphere is nearly free of water vapor. Sublimation of an element or compound is a transition from the Solid to Gas phase with no intermediate liquid stage Evaporation is the process by which Molecules in a Liquid state (e The haze in Titan's atmosphere contributes to the moon's anti-greenhouse effect by reflecting sunlight away from the satellite, making its surface significantly colder than its upper atmosphere. Haze is traditionally an atmospheric phenomenon where dust smoke and other dry particles obscure the clarity of the sky The anti-greenhouse effect is a Neologism used to describe two different effects coming under the header of "the cooling effect an atmosphere has on the ambient temperature ^[63] The clouds on Titan, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze. ^[16] This atmospheric methane conversely creates a greenhouse effect on Titan's surface, without which Titan would be far colder. The Greenhouse effect refers to the change in the Thermal equilibrium temperature of a planet or moon by the presence of an Atmosphere containing gas that absorbs ^[64] The findings of the Huygens probe indicate that Titan's atmosphere periodically rains liquid methane and other organic compounds onto the moon's surface. ^[65] In October 2007, observers noted an increase in apparent opacity in the clouds above the equatorial Xanadu region, suggestive of "methane drizzle", though this was not direct evidence for rain. Xanadu (often called "Xanadu Regio" though this is not its official name is a highly reflective area on ^[66] It is possible that areas of Titan's surface may be coated in a layer of tholins, but this has not been confirmed. ^[67]

Simulations of global wind patterns based on wind speed data taken by Huygens during its descent have suggested that Titan's atmosphere circulates in a single enormous Hadley cell. The Hadley cell is a circulation pattern that dominates the tropical atmosphere with rising motion near the equator poleward flow 10-15 kilometers above the surface descending motion Warm air rises in Titan's southern hemisphere—which was experiencing summer during Huygens' descent—and sinks in the northern hemisphere, resulting in high-altitude air flow from south to north and low-altitude airflow from north to south. Such a large Hadley cell is only possible on a slowly rotating world such as Titan. ^[30] The pole-to-pole wind circulation cell appears to be centered on 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). ^[68] This cell creates a global band of low pressure—what is in effect a variation of Earth's Intertropical Convergence Zone. The Intertropical Convergence Zone (ITCZ, also known as the Intertropical Front, Monsoon trough, Doldrums or the Equatorial Unlike on Earth, however, where the oceans confine the ITCZ to the tropics, on Titan, the zone wanders from one pole to the other, taking methane rainclouds with it. This means that Titan, despite its frigid temperatures, can be said to have a tropical climate. ^[69]

The number of methane lakes visible near Titan's southern pole is decidedly smaller than the number observed near the north pole. As the south pole is currently in summer and the north in winter, an emerging hypothesis is that methane rains onto the poles in winter and evaporates in summer. ^[70]

Clouds

A cloud imaged in false colour over Titan's north pole

In September 2006, Cassini imaged a large cloud at a height of 40 km over Titan's north pole. Although methane 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. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre In December, Cassini again observed cloud cover and detected methane, ethane and other organics. The cloud was over 2,400 km in diameter and was still visible during a following flyby a month later. One hypothesis 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-hypothesised "methanological" cycle (analogous to Earth's hydrological cycle) on Titan. The Earth 's Water is always in movement and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on above ^[71]

Clouds have also been found over the south pole. While typically covering 1% of Titan's disk, 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. Insolation is a measure of Solar radiation energy received on a given surface area in a given time Convection in the most general terms refers to the movement of molecules within Fluids (i 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. ^[72] It is currently summer in Titan's southern hemisphere and will remain so until 2010, when Saturn's orbit, which governs the moon's motion, will tilt the northern hemisphere towards the Sun. ^[30] When the seasons switch, ethane will begin to condense over the south pole. ^[73]

Research models that match well with observations suggest that clouds on Titan cluster at preferred coordinates and that cloud cover varies by distance from 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. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and In the summer hemisphere, frequent, thick but sporadic methane clouds seem to cluster around 40°. ^[68]

Ground-based observations also reveal seasonal variations in cloud cover. Over 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. ^[71]

Observation and exploration

Cassini image of Epimetheus and Titan

Titan is never visible to the naked eye, but can be observed through small telescopes or strong binoculars. TemplateInfobox Planet.--> Epimetheus (ˌɛpɨˈmiːθiəs,, or Amateur observation is difficult because of the proximity of the satellite 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. ^[74] Titan has a maximum apparent magnitude of +7. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 9. This compares to +4. 6 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 suggested that he had observed darkening near the edges of Titan's disk and two round, white patches in its center. The deduction of an atmosphere by Kuiper in the 1940s was the next major observational event. ^[75]

The first probe to visit the Saturnian system was Pioneer 11 in 1979, which determined that Titan was likely too cold to support life. Pioneer 11 was the second mission (after its sister probe Pioneer 10) to investigate Jupiter and the Outer solar system and the first to explore the planet ^[76] The craft took the first images of the moon (including some of it and Saturn together), but these were of low quality; the first-ever close-up of Titan was taken on September 2, 1979. Events 44 BC - Pharaoh Cleopatra VII of Egypt declares her son co-ruler as Ptolemy XV Caesarion. Year 1979 ( MCMLXXIX) was a Common year starting on Monday (link displays the 1979 Gregorian calendar) ^[77]

Titan was examined by both Voyager 1 and Voyager 2 in 1980 and 1981, respectively. The Voyager 1 spacecraft is a 722-kilogram robotic Space probe of the outer Solar system and beyond launched September 5, Voyager 2 is an unmanned Interplanetary Spacecraft launched on August 20, 1977. 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, 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,^[78] but by then they had already been observed in the infrared by the Hubble Space Telescope. Xanadu (often called "Xanadu Regio" though this is not its official name is a highly reflective area on Shangri-la is a large dark region of Saturn 's moon Titan. It is named after Shangri-La, the mythical paradise in Tibet. Voyager 2 took only a cursory look at Titan. The Voyager 2 team had the option of steering the spacecraft to take a detailed look at Titan or to use another trajectory which would allow it to visit Uranus and Neptune. Given the lack of surface features seen by Voyager 1, the latter plan was implemented.

Cassini–Huygens

Main articles: Cassini–Huygens and Huygens probe

Even with the data provided by the Voyagers, Titan remained a body of mystery—a planet-like satellite shrouded in an atmosphere that makes detailed observation difficult. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its The Huygens probe, supplied by the European Space Agency (ESA and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry The intrigue that had surrounded Titan since the 17th-century observations of Christiaan Huygens and Giovanni Cassini was finally gratified by the spacecraft named in their honor.

The Cassini–Huygens spacecraft reached Saturn on July 1, 2004 and has begun the process of mapping Titan's surface by radar. "July 1st" redirects here For the Ayumi Hamasaki song see H (song. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships A joint project of the European Space Agency (ESA) and NASA, Cassini–Huygens, has proved a very successful mission. The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member The Cassini probe flew by Titan on October 26, 2004 and took the highest-resolution images ever of the moon's surface, at only 1,200 km, discerning patches of light and dark that would be invisible to the human eye from the Earth. Events 740 - An Earthquake strikes Constantinople, causing much damage and death "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Huygens landed on Titan on January 14, 2005, discovering that many of the moon's surface features seem to have been formed by flowing fluids at some point in the past. Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. ^[79] On July 22, 2006, Cassini made the first of a series of 21 planned, targeted, close fly-bys, each at only 950 km from Titan; the last is scheduled for May 12, 2008. Events 1099 - First Crusade: Godfrey of Bouillon is elected the first Defender of the Holy Sepulchre of The Kingdom of Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1191 - Richard I of England marries Berengaria of Navarre. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common ^[80] Present liquid on the surface may have been found near the north pole, in the form of many lakes that were recently discovered by Cassini. ^[42] Titan is the most distant body from Earth that has seen a space probe landing. ^[81] Titan is also the second moon in the solar system to have a man-made object land on its surface.

Huygens landing site

Huygens image from Titan's surface

The Huygens probe landed just off the easternmost tip of a bright region now called Adiri, where it photographed pale hills with dark "rivers" running down to a dark plain. The Huygens probe, supplied by the European Space Agency (ESA and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry Adiri is a large bright Albedo feature on Saturn 's moon Titan. 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 the hills with the methane rain and are deposited on the plains over geological time scales. ^[52]

After landing, Huygens photographed a dark plain covered in small rocks and pebbles, which are composed of water ice. ^[52] The two rocks just below the middle of the image on the left 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. Fluvial is used in Geography and Earth science to refer to the deposits and landforms created by the action of rivers or streams and the processes associated with The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon ice. It is believed 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 Station in memory of the former president of the ESA. The Committee on Space Research ( COSPAR) was established by the International Council for Science in 1958. Hubert Curien ( October 30 1924 - February 6 2005) was a French Physicist and a key figure in European science politics ^[82]

Prebiotic conditions and possible life

See also: Planetary habitability

Scientists believe that the atmosphere of early Earth was similar in composition to the current atmosphere on Titan. Planetary habitability is the measure of a Planet 's or a Natural satellite 's potential to develop and sustain Life. Many hypotheses have developed that attempt to bridge the step from chemical to biological evolution. 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 Miller-Urey experiment (or Urey-Miller experiment) was an Experiment that simulated hypothetical conditions present on the Early Earth and tested Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Tholin (after the Greek word for muddy is a Heteropolymer formed by solar Ultraviolet irradiation of simple Organic compounds such as Methane The reaction starts with dissociation of nitrogen and methane, forming hydrocyan and ethyne. Dissociation in Chemistry and Biochemistry is a general process in which ionic compounds ( complexes, Molecules, or Salts) separate Hydrogen cyanide is a Chemical compound with Chemical formula HCN Acetylene ( IUPAC name ethyne), C2H2 is a Hydrocarbon belonging to the group of Alkynes It is the simplest of all alkynes Further reactions have been studied extensively. ^[83]

All of these experiments have led to the suggestion that enough organic material exists on Titan to start a chemical evolution analogous to what is thought to have started life on Earth. While the analogy assumes the presence of liquid water for longer periods than is currently observable, several theories suggest that liquid water from an impact could be preserved under a frozen isolation layer. ^[84] It has also been observed that liquid ammonia oceans could exist deep below the surface;^[9][85] one model suggests an ammonia–water solution as much as 200 km deep beneath a water ice crust, conditions that, "while extreme by terrestrial standards, are such that life could indeed survive". ^[10] Heat transfer between the interior and upper layers would be critical in sustaining any sub-surface oceanic life. In thermal physics, heat transfer is the passage of Thermal energy from a hot to a colder body ^[9]

Detection of microbial life on Titan would depend on its biogenic effects. That the atmospheric methane and nitrogen are of biological origin has been examined, for example. ^[10] Hydrogen has been cited as one molecule suitable to test for life on Titan: if methanogenic life is consuming atmospheric hydrogen in sufficient volume, it will have a measurable effect on the mixing ratio in the troposphere. The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and ^[86]

Despite these biological possibilities, there are formidable obstacles to life on Titan, and any analogy to Earth is inexact. At a vast distance from the Sun, Titan is frigid (a fact exacerbated by the anti-greenhouse effect of its cloud cover), and its atmosphere lacks CO₂. The Sun (Sol is the Star at the center of the Solar System. The anti-greenhouse effect is a Neologism used to describe two different effects coming under the header of "the cooling effect an atmosphere has on the ambient temperature Given these difficulties, the topic of life on Titan may be best described as an experiment for examining theories on conditions necessary prior to flourishing life on Earth. ^[87] While life itself may not exist, the prebiotic conditions of the Titanian environment, and the possible presence of organic chemistry, remain of great interest in understanding the early history of the terrestrial biosphere. ^[88] Using Titan as a prebiotic experiment involves not only observation through spacecraft, but laboratory experiment, and chemical and photochemical modelling on Earth. ^[83]

An alternate explanation for life's hypothetical existence on Titan has been proposed: if life were to be found on Titan, it would be statistically more likely to have originated from Earth than to have appeared independently, a process known as panspermia. Panspermia ( Gk. πάς/πάν (pas/pan all and σπέρμα ( sperma, seed is the Hypothesis that "seeds" of Life exist already It is theorized that large asteroid and cometary impacts on Earth's surface have caused hundreds of millions of fragments of microbe-laden rock to escape Earth's gravity. Calculations indicate that a number of these would encounter many of the bodies in the solar system, including Titan. ^[89][90]

Conditions on Titan could become far more habitable in future. Six billion years from now, as the Sun becomes a red giant, surface temperatures could rise to ~200K, high enough for stable oceans of water/ammonia mixture to exist on the surface. A red giant is a luminous Giant star of low or intermediate mass (roughly 0 As the Sun's ultraviolet output decreases, the haze in Titan's upper atmosphere will deplete, lessening the anti-greenhouse effect on the surface and enabling the greenhouse created by atmospheric methane to play a far greater role. These conditions together could create an environment agreeable to exotic forms of life, and will subsist for several hundred million years, long enough for at least primitive life to form. ^[91]

While the Cassini–Huygens mission was not equipped to provide evidence for biology or complex organics, it did support the theory of an environment on Titan that is similar, in some ways, to that of the primordial Earth. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its ^[88]

There are a wide range of options for future missions to Titan that might address these and other questions,^[92] including orbiters, landers, balloons etc.

See also

• Colonization of Titan
• Huygens probe
• List of planetary bodies
• List of Solar System objects by radius
• Saturn's moons in fiction
• Timeline of discovery of Solar System planets and their moons
• Titan in fiction

References

Further reading

• Lorenz, Ralph; Jacqueline Mitton (May 2002). Lifting Titan's Veil: Exploring the Giant Moon of Saturn. Cambridge University Press. ISBN 0-521-79348-3.  

External links

• The Alien Noise. This recording is a laboratory reconstruction of the sounds heard by Huygens' microphones.
• Cassini-Huygens Mission To Saturn & Titan. Multimedia Feature Titan Virtual Tour
• Titan Profile by NASA's Solar System Exploration
• Cassini Imaging Central Laboratory for Operations (2005). CICLOPS: Cassini Imaging. Retrieved March 28, 2005.
• European Space Agency. The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member (2005). ESA - Cassini-Huygens. Retrieved March 28, 2005.
• Gangale, Thomas (2002). The Darian Calendar for Titan. Retrieved March 28, 2005.
• Hamilton, Calvin J. (2001). Titan - Saturn IV. Retrieved March 28, 2005.
• Hammerschlag, Michael (2005). CLOUD WORLD: MISSION to TITAN. Retrieved March 28, 2005.
• NASA (2005). The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program NASA - Cassini-Huygens: Close Encounter With Saturn. Retrieved March 28, 2005.
• Perry, Jason (2005). Titan Today. Retrieved March 28, 2005.
• The Planetary Society (2005). The Planetary Society is a large publicly supported non-government and not-for-profit organization that has many research projects related to Astronomy. TPS: Saturn's moon Titan. Retrieved March 28, 2005.
• University of Arizona Lunar and Planetary Lab (2005). The University of Arizona (also referred to as UA, U of A, or Arizona) is a Land-grant and space-grant public institution Lunar and Planetary Lab The Descent Imager-Spectral Radiometer of the Cassini-Huygens Mission to Titan. Retrieved March 28, 2005.
• Video of Huygens’ descent from the ESA