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Titan (moon)

Titan is the largest moon of Saturn and the second-largest in the Solar System. It is the only moon known to have an atmosphere denser than the Earth's, and is the only known object in space other than Earth on which clear evidence of stable bodies of surface liquid has been found.[16] Titan is one of the seven gravitationally rounded moons of Saturn and the second-most distant among them. Frequently described as a planet-like moon, Titan is 50% larger (in diameter) than Earth's Moon and 80% more massive. It is the second-largest moon in the Solar System after Jupiter's moon Ganymede, and is larger than Mercury, but only 40% as massive due to Mercury being made of mostly dense iron and rock, while a large portion of Titan is made of less-dense ice.

Not to be confused with Titania (moon) or Triton (moon).

Discovery

Christiaan Huygens

March 25, 1655

Saturn VI

/ˈtaɪtən/ [1]

Τῑτάν Tītan

Titanian[2] or Titanean[3] (both /taɪˈteɪniən/)[4][5]

1186680 km

1257060 km

1221870 km

0.0288

15.945 d

5.57 km/s (calculated)

0.34854° (to Saturn's equator)

Saturn

2574.73±0.09 km (0.404 Earths)[7]

8.3×107 km2 (0.163 Earths)

7.16×1010 km3 (0.066 Earths)

(1.3452±0.0002)×1023 kg
(0.0225 Earth's)[8]

1.8798±0.0044 g/cm3[8]

1.352 m/s2 (0.138 g)

0.3414±0.0005[9] (estimate)

2.641 km/s

Synchronous

Zero (to the orbital plane);
27° (to the sun)

0.22 (geometric) [10] 0.265±0.03 (Bond)[11]

93.7 K (−179.5 °C)[12]

8.2[13] to 9.0

146.7 kPa (1.45 atm)

Variable

Stratosphere:
98.4% nitrogen (N
2),
1.4% methane (CH
4),
0.2% hydrogen (H
2);

Lower troposphere:
95.0% N
2, 4.9% CH
4;[14]
97% N
2, 2.7±0.1% CH
4, 0.1–0.2% H
2[15]

Discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan was the first known moon of Saturn, and the sixth known planetary satellite (after Earth's moon and the four Galilean moons of Jupiter). Titan orbits Saturn at 20 Saturn radii, or 1,200,000 km above Saturn's apparent surface. From Titan's surface, Saturn subtends an arc of 5.09 degrees, and if it were visible through the moon's thick atmosphere, it would appear 11.4 times larger in the sky, in diameter, than the Moon from Earth, which subtends 0.48° of arc.


Titan is primarily composed of ice and rocky material, which is likely differentiated into a rocky core surrounded by various layers of ice, including a crust of ice Ih and a subsurface layer of ammonia-rich liquid water.[17] Much as with Venus before the Space Age, the dense opaque atmosphere prevented understanding of Titan's surface until the Cassini–Huygens mission in 2004 provided new information, including the discovery of liquid hydrocarbon lakes in Titan's polar regions and the discovery of its atmospheric super-rotation. The geologically young surface is generally smooth, with few impact craters, although mountains and several possible cryovolcanoes have been found.


The atmosphere of Titan is largely nitrogen; minor components lead to the formation of methane and ethane clouds and heavy organonitrogen haze. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas (probably of liquid methane and ethane), and deltas, and is dominated by seasonal weather patterns as on Earth. With its liquids (both surface and subsurface) and robust nitrogen atmosphere, Titan's methane cycle bears a striking similarity to Earth's water cycle, albeit at the much lower temperature of about 94 K (−179 °C; −290 °F). Due to these factors, Titan has been described as the most Earth-like celestial object in the Solar System.[18]

Formation[edit]

The regular 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. As the young gas giants formed, they were surrounded by discs of material that gradually coalesced into moons. 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. 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.[43]


A 2014 analysis of Titan's atmospheric nitrogen suggested that it was possibly sourced from material similar to that found in the Oort cloud and not from sources present during the co-accretion of materials around Saturn.[44]

Global map of Titan – with IAU labels (August 2016).

Global map of Titan – with IAU labels (August 2016).

Titan's North Pole (2014)

Titan's North Pole (2014)

Titan's South Pole (2014)

Titan's South Pole (2014)

The first ever close-up image of Titan, taken by Pioneer 11 on September 1, 1979, from a distance of 3,540,000 kilometres or 2,200,000 miles.[222]

The first ever close-up image of Titan, taken by Pioneer 11 on September 1, 1979, from a distance of 3,540,000 kilometres or 2,200,000 miles.[222]

An improved image of Titan by Voyager 1, taken on November 11, 1980, during a targeted flyby from a distance of 4,000 kilometres or 2,500 miles.[223][224]

An improved image of Titan by Voyager 1, taken on November 11, 1980, during a targeted flyby from a distance of 4,000 kilometres or 2,500 miles.[223][224]

Another image of Titan taken by Voyager 2 on August 23, 1981, a few months after Voyager 1 arrived at Saturn first. The spacecraft was around 2,300,000 kilometres or 1,400,000 miles away from the moon.[225]

Another image of Titan taken by Voyager 2 on August 23, 1981, a few months after Voyager 1 arrived at Saturn first. The spacecraft was around 2,300,000 kilometres or 1,400,000 miles away from the moon.[225]

An image of Titan's nightside taken by Voyager 2 on August 25, 1981, as it departed the Saturnian system. The hazy atmosphere of Titan scatters sunlight from its dayside around the entire moon, causing Titan to light up like a ring.

An image of Titan's nightside taken by Voyager 2 on August 25, 1981, as it departed the Saturnian system. The hazy atmosphere of Titan scatters sunlight from its dayside around the entire moon, causing Titan to light up like a ring.

The Saturn-facing side of Titan and Rhea (Saturn's second-largest moon), imaged on July 16, 2011, by the Cassini spacecraft as Rhea passed in front of Titan.[226] Titan's massive atmosphere can be clearly seen as a bluish haze around the yellow moon; while Rhea obviously has no such atmosphere.

The Saturn-facing side of Titan and Rhea (Saturn's second-largest moon), imaged on July 16, 2011, by the Cassini spacecraft as Rhea passed in front of Titan.[226] Titan's massive atmosphere can be clearly seen as a bluish haze around the yellow moon; while Rhea obviously has no such atmosphere.

Titan (largest) together with Rhea and Mimas (smallest) in crescent shape, forming a triple crescent.[227] Titan's massive atmosphere is clearly seen extending out into space, while Rhea and Mimas have none.

Titan (largest) together with Rhea and Mimas (smallest) in crescent shape, forming a triple crescent.[227] Titan's massive atmosphere is clearly seen extending out into space, while Rhea and Mimas have none.

An image of Titan in front Saturn as the smaller moon Dione passes behind its fellow moon. The north pole of Titan is covered by an atmospheric hood which appears as a detached layer at the top of the moon. Imaged on May 21, 2011, by the Cassini spacecraft.[226]

An image of Titan in front Saturn as the smaller moon Dione passes behind its fellow moon. The north pole of Titan is covered by an atmospheric hood which appears as a detached layer at the top of the moon. Imaged on May 21, 2011, by the Cassini spacecraft.[226]

Tethys as it moves pass behind the atmospheric halo of Titan. Tethys is actually not entering Titan's atmosphere as the two are 1,200,000 kilometres or 750,000 miles from each other in this image. Imaged on November 26, 2011, by the Cassini spacecraft.[228]

Tethys as it moves pass behind the atmospheric halo of Titan. Tethys is actually not entering Titan's atmosphere as the two are 1,200,000 kilometres or 750,000 miles from each other in this image. Imaged on November 26, 2011, by the Cassini spacecraft.[228]

A highly improved version of Titan's nightside compared to Voyager 2's older nightside photograph. Imaged by the more-advanced Cassini spacecraft on October 12, 2009.[229]

A highly improved version of Titan's nightside compared to Voyager 2's older nightside photograph. Imaged by the more-advanced Cassini spacecraft on October 12, 2009.[229]

Close view of Titan with Saturn in the background.

Close view of Titan with Saturn in the background.

Coustenis, Athéna; Taylor, F. W. (2008). . World Scientific. ISBN 978-981-270-501-3.

Titan: Exploring an Earthlike World

Lorenz, Ralph; (2002). Lifting Titan's Veil: Exploring the Giant Moon of Saturn. Cambridge University Press. ISBN 978-0-521-79348-3.

Mitton, Jacqueline

Lorenz, Ralph; Mitton, Jacqueline (2008). . Princeton University Press. ISBN 978-0-691-14633-1.

Titan Unveiled

Lorenz, Ralph (2017). NASA/ESA/ASI Cassini-Huygens: 1997 onwards (Cassini orbiter, Huygens probe and future exploration concepts) (Owners' Workshop Manual). Haynes Manuals, UK.  978-1-78521-111-9.

ISBN

O'Callaghan, Jonathan (November 21, 2019). (PDF). Nature. 575 (7783): 426–427. Bibcode:2019Natur.575..426O. doi:10.1038/d41586-019-03539-8. PMID 31745360. S2CID 208171884.

"A Map of Saturn's Largest Moon"

. Multimedia Feature Titan Virtual Tour

Cassini–Huygens Mission To Saturn and Titan

from the ESA

Video of Huygens’ descent

Archived February 20, 2022, at the Wayback Machine

Cassini Imaging Central Laboratory for Operations (CICLOPS) site Titan image search

The (2005). TPS: Saturn's moon Titan. Retrieved March 28, 2005.

Planetary Society

. This recording is a laboratory reconstruction of the sounds heard by Huygens' microphones.

The Alien Noise

Archived October 12, 2011, at the Wayback Machine Fraser Cain and Pamela Gay, 2010.

AstronomyCast: Titan

and Titan map with feature names from the USGS planetary nomenclature page

Titan nomenclature

interactive map of the moon

Google Titan 3D

by Kevin M. Gill

Image album