Titan (or Saturn VI)

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 I_h 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]