Triton (moon)

Short description: Largest moon of Neptune

Triton

Rendered image of Triton's south polar region created with Voyager 2 imagery

Discovery
Discovered by| William Lassell
Discovery date| October 10, 1846
Designations

Designation

| Neptune I
Pronunciation| /ˈtraɪtən/
Named after| Τρίτων Trītōn
Adjectives| Tritonian (/traɪˈtoʊniən/)[1]
Orbital characteristics

Semi-major axis

| 354,759 km
Eccentricity| 0.000016[2]
Orbital period| 5.876854 d
(retrograde)[2][3]
Average Orbital speed| 4.39 km/s[lower-alpha 1]
Inclination| 129.812° (to the ecliptic)
156.885° (to Neptune's equator)[4][5]
129.608° (to Neptune's orbit)
Satellite of| Neptune
Physical characteristics
Mean radius| 1,353.4±0.9 km[6] (0.2122 R⊕)
Surface area| 23,018,000 km2[lower-alpha 2]
Volume| 10,384,000,000 km3[lower-alpha 3]
Mass| (2.1390±0.0028)×1022 kg
(0.00359 Earths)[lower-alpha 4]
Mean density| 2.061 g/cm3[6]

surface gravity

| 0.779 m/s2 (0.0794 g) (0.48 Moons)[lower-alpha 5]

escape velocity

| 1.455 km/s[lower-alpha 6]
Rotation period| synchronous
Sidereal rotation period| 5 d, 21 h, 2 min, 53 s[7]
Axial tilt| 0[lower-alpha 7]
Albedo| 0.76[6]
Physics| 38 K (−235.2 °C)[7]
Apparent magnitude| 13.47[8]
Absolute magnitude (H)| −1.2[9]
Atmosphere
Surface pressure| 1.4 to 1.9 Pa (1.38×10−5 to 1.88×10−5 atm)[7][11]
Composition by volume| nitrogen; methane traces[10]

Triton is the largest natural satellite of the planet Neptune, and was the first Neptunian moon to be discovered, on October 10, 1846, by English astronomer William Lassell. It is the only large moon in the Solar System with a retrograde orbit, an orbit in the direction opposite to its planet's rotation.[3][12] Because of its retrograde orbit and composition similar to Pluto, Triton is thought to have been a dwarf planet, captured from the Kuiper belt.[13]

At 2,710 kilometers (1,680 mi)[6] in diameter, it is the seventh-largest moon in the Solar System, the only satellite of Neptune massive enough to be in hydrostatic equilibrium, the second-largest planetary moon in relation to its primary (after Earth's Moon), and larger than Pluto. Triton is one of the few moons in the Solar System known to be geologically active (the others being Jupiter's Io and Europa, and Saturn's Enceladus and Titan) as well as suspected to contain an internal, active layer of liquid ocean, similar to the aforementioned moons. As a consequence, its surface is relatively young, with few obvious impact craters. Intricate cryovolcanic and tectonic terrains suggest a complex geological history. Triton has a surface of mostly frozen nitrogen, a mostly water-ice crust,[14] an icy mantle and a substantial core of rock and metal. The core makes up two-thirds of its total mass. The mean density is 2.061 g/cm3,[6] reflecting a composition of approximately 15–35% water ice.[7]

During its 1989 flyby of Triton, Voyager 2 found surface temperatures of 38 K (−235 °C) and also discovered active geysers erupting sublimated nitrogen gas, contributing to a tenuous nitrogen atmosphere less than ​1⁄70,000 the pressure of Earth's atmosphere at sea level.[7] Voyager 2 remains the only spacecraft to have visited Triton.[15] As the probe was only able to study about 40% of the moon's surface, future missions (including a flyby mission dubbed Trident and Neptune orbiters dubbed Triton Ocean Worlds Surveyor and Nautilus) have been proposed to NASA via their New Frontiers and Discovery programs to revisit the Neptune system with a focus on Triton; and its subsurface ocean.[16][17]

## Contents

* 1 Discovery and naming
* 2 Orbit and rotation
* 3 Capture
* 4 Physical characteristics
* 5 Atmosphere
* 6 Surface features
* 6.1 Cryovolcanism
* 6.2 Polar cap, plains and ridges
* 6.3 Cantaloupe terrain
* 6.4 Impact craters
* 7 Observation and exploration
* 8 Maps
* 9 See also
* 10 Notes
* 11 References
* 12 External links

## Discovery and naming

William Lassell, the discoverer of Triton

Triton was discovered by British astronomer William Lassell on October 10, 1846,[18] just 17 days after the discovery of Neptune. When John Herschel received news of Neptune's discovery, he wrote to Lassell suggesting he search for possible moons. Lassell discovered Triton eight days later.[18][19] Lassell also claimed for a period[lower-alpha 8] to have discovered rings.[20] Although Neptune was later confirmed to have rings, they are so faint and dark that it is not plausible he saw them. A brewer by trade, Lassell spotted Triton with his self-built 61 cm (24 in) aperture metal mirror reflecting telescope (also known as the "two-foot" reflector).[21] This telescope was donated to the Royal Observatory, Greenwich in the 1880s, but was eventually dismantled.[21]

Triton is named after the Greek sea god Triton (Τρίτων), the son of Poseidon (the Greek god corresponding to the Roman Neptune). The name was first proposed by Camille Flammarion in his 1880 book Astronomie Populaire,[22] and was officially adopted many decades later.[23] Until the discovery of the second moon Nereid in 1949, Triton was commonly referred to as "the satellite of Neptune". Lassell did not name his discovery; he later successfully suggested the name Hyperion, previously chosen by John Herschel, for the eighth moon of Saturn when he discovered it.[24]

## Orbit and rotation

The orbit of Triton (red) is opposite in direction and tilted −23° compared to a typical moon's orbit (green) in the plane of Neptune's equator.

Triton is unique among all large moons in the Solar System for its retrograde orbit around its planet (i.e. it orbits in a direction opposite to the planet's rotation). Most of the outer irregular moons of Jupiter and Saturn also have retrograde orbits, as do some of Uranus's outer moons. However, these moons are all much more distant from their primaries, and are small in comparison; the largest of them (Phoebe)[lower-alpha 9] has only 8% of the diameter (and 0.03% of the mass) of Triton.

Triton's orbit is associated with two tilts, the obliquity of Neptune's rotation to Neptune's orbit, 30°, and the inclination of Triton's orbit to Neptune's rotation, 157° (an inclination over 90° indicates retrograde motion). Triton's orbit precesses forward relative to Neptune's rotation with a period of about 678 Earth years (4.1 Neptunian years),[4][5] making its Neptune-orbit-relative inclination vary between 127° and 173°. That inclination is currently 130°; Triton's orbit is now near its maximum departure from coplanarity with Neptune's.

Triton's rotation is tidally locked to be synchronous with its orbit around Neptune: it keeps one face oriented toward the planet at all times. Its equator is almost exactly aligned with its orbital plane.[25] At present, Triton's rotational axis is about 40° from Neptune's orbital plane, and hence as Neptune orbits the Sun, Triton's polar regions take turns facing the Sun, resulting in seasonal changes as one pole, then the other moves into the sunlight. Such changes were observed in 2010.[26]

Triton's revolution around Neptune has become a nearly perfect circle with an eccentricity of almost zero. Viscoelastic damping from tides alone is not thought to be capable of circularizing Triton's orbit in the time since the origin of the system, and gas drag from a prograde debris disc is likely to have played a substantial role.[4][5] Tidal interactions also cause Triton's orbit, which is already closer to Neptune than the Moon is to Earth, to gradually decay further; predictions are that 3.6 billion years from now, Triton will pass within Neptune's Roche limit.[27] This will result in either a collision with Neptune's atmosphere or the breakup of Triton, forming a new ring system similar to that found around Saturn.[27]

## Capture

The Kuiper belt (green), in the Solar System's outskirts, is where Triton is thought to have originated.

The current understanding of moons in retrograde orbits means they cannot form in the same region of the solar nebula as the planets they orbit. Therefore Triton must have been captured from elsewhere in the solar system. Astrophysicists believe it might have originated in the Kuiper belt,[13] a ring of small icy objects extending from just inside the orbit of Neptune to about 50 AU from the Sun. Thought to be the point of origin for the majority of short-period comets observed from Earth, the belt is also home to several large, planet-like bodies including Pluto, which is now recognized as the largest in a population of Kuiper belt objects (the plutinos) locked in resonant orbits with Neptune. Triton is only slightly larger than Pluto and is nearly identical in composition, which has led to the hypothesis that the two share a common origin.[28]

The proposed capture of Triton may explain several features of the Neptunian system, including the extremely eccentric orbit of Neptune's moon Nereid and the scarcity of moons as compared to the other giant planets. Triton's initially eccentric orbit would have intersected the orbits of irregular moons and disrupted those of smaller regular moons, dispersing them through gravitational interactions.[4][5]

Triton's eccentric post-capture orbit would have also resulted in tidal heating of its interior, which could have kept Triton fluid for a billion years; this inference is supported by evidence of differentiation in Triton's interior. This source of internal heat disappeared following tidal locking and circularization of the orbit.[29]

Two types of mechanisms have been proposed for Triton's capture. To be gravitationally captured by a planet, a passing body must lose sufficient energy to be slowed down to a speed less than that required to escape.[7] An early theory of how Triton may have been slowed was by collision with another object, either one that happened to be passing by Neptune (which is unlikely), or a moon or proto-moon in orbit around Neptune (which is more likely).[7] A more recent hypothesis suggests that, before its capture, Triton was part of a binary system. When this binary encountered Neptune, it interacted in such a way that the binary dissociated, with one portion of the binary expelled, and the other, Triton, becoming bound to Neptune. This event is more likely for more massive companions.[13] This hypothesis is supported by several lines of evidence, including binaries being very common among the large Kuiper belt objects.[30][31] The event was brief but gentle, saving Triton from collisional disruption. Events like this may have been common during the formation of Neptune, or later when it migrated outward.[13]

However, simulations in 2017 showed that after Triton's capture, and before its orbital eccentricity decreased, it probably did collide with at least one other moon, and caused collisions between other moons.[32][33]

## Physical characteristics

Triton dominates the Neptunian moon system, with over 99.5% of its total mass. This imbalance may reflect the elimination of many of Neptune's original satellites following Triton's capture.[4][5]

Triton (lower left) compared to the Moon (upper left) and Earth (right), to scale

Triton is the seventh-largest moon and sixteenth-largest object in the Solar System and is modestly larger than the dwarf planets Pluto and Eris. It is also the largest retrograde moon in the solar system. It comprises more than 99.5% of all the mass known to orbit Neptune, including the planet's rings and thirteen other known moons,[lower-alpha 10] and is also more massive than all known moons in the Solar System smaller than itself combined.[lower-alpha 11] Also, with a diameter 5.5% that of Neptune, it is the largest moon of a gas giant relative to its planet in terms of diameter, although Titan is bigger relative to Saturn in terms of mass (the ratio of Triton's mass to that of Neptune is approximately 1:4788). It has a radius, density (2.061 g/cm3), temperature and chemical composition similar to that of Pluto.[34]

Triton's surface is covered with a transparent layer of annealed frozen nitrogen. Only 40% of Triton's surface has been observed and studied, but it may be entirely covered in such a thin sheet of nitrogen ice. Like Pluto's, Triton's crust consists of 55% nitrogen ice with other ices mixed in. Water ice comprises 15–35% and frozen carbon dioxide (dry ice) the remaining 10–20%. Trace ices include 0.1% methane and 0.05% carbon monoxide.[7] There could also be ammonia ice on the surface, as there are indications of ammonia dihydrate in the lithosphere.[35] Triton's mean density implies that it probably consists of about 30–45% water ice (including relatively small amounts of volatile ices), with the remainder being rocky material.[7] Triton's surface area is 23 million km2, which is 4.5% of Earth, or 15.5% of Earth's land area. Triton has an unusually high albedo, reflecting 60–95% of the sunlight that reaches it, and it has changed only slightly since the first observations. By comparison, the Moon reflects only 11%.[36] This high albedo causes Triton to reflect a lot of whatever little sunlight there is instead of absorbing it,[37][38] causing it to have the coldest recorded temperature in the Solar System at 38 K (−235 °C).[39][40] Triton's reddish color is thought to be the result of methane ice, which is converted to tholins under exposure to ultraviolet radiation.[7][41]

Because Triton's surface indicates a long history of melting, models of its interior posit that Triton is differentiated, like Earth, into a solid core, a mantle and a crust. Water, the most abundant volatile in the Solar System, comprises Triton's mantle, enveloping a core of rock and metal. There is enough rock in Triton's interior for radioactive decay to maintain a liquid subsurface ocean to this day, similar to what is thought to exist beneath the surface of Europa and several other icy outer Solar System worlds.[7][42][43][44] This is not thought to be adequate to power convection in Triton's icy crust. However, the strong obliquity tides are believed to generate enough additional heat to accomplish this and produce the observed signs of recent surface geological activity.[44] The black material ejected is suspected to contain organic compounds,[43] and if liquid water is present on Triton, it has been speculated that this could make it habitable for some form of life.[43][45][46]

## Atmosphere

Main article: Astronomy:Atmosphere of Triton

Artist's impression of Triton, showing its tenuous atmosphere just over the limb.

Triton has a tenuous nitrogen atmosphere, with trace amounts of carbon monoxide and small amounts of methane near its surface.[10][47][48] Like Pluto's atmosphere, the atmosphere of Triton is thought to have resulted from the evaporation of nitrogen from its surface.[28] Its surface temperature is at least 35.6 K (−237.6 °C) because Triton's nitrogen ice is in the warmer, hexagonal crystalline state, and the phase transition between hexagonal and cubic nitrogen ice occurs at that temperature.[49] An upper limit in the low 40s (K) can be set from vapor pressure equilibrium with nitrogen gas in Triton's atmosphere.[50] This is colder than Pluto's average equilibrium temperature of 44 K (−229.2 °C). Triton's surface atmospheric pressure is only about 1.4–1.9 Pa (0.014–0.019 mbar).[7]

Clouds observed above Triton's limb by Voyager 2.

Turbulence at Triton's surface creates a troposphere (a "weather region") rising to an altitude of 8 km. Streaks on Triton's surface left by geyser plumes suggest that the troposphere is driven by seasonal winds capable of moving material over a micrometer in size.[51] Unlike other atmospheres, Triton's lacks a stratosphere and instead has a thermosphere from altitudes of 8 to 950 km and an exosphere above that.[7] The temperature of Triton's upper atmosphere, at 95±5 K, is higher than that at its surface, due to heat absorbed from solar radiation and Neptune's magnetosphere.[10][52] A haze permeates most of Triton's troposphere, thought to be composed largely of hydrocarbons and nitriles created by the action of sunlight on methane. Triton's atmosphere also has clouds of condensed nitrogen that lie between 1 and 3 km from its surface.[7]

In 1997, observations from Earth were made of Triton's limb as it passed in front of stars. These observations indicated the presence of a denser atmosphere than was deduced from Voyager 2 data.[53] Other observations have shown an increase in temperature by 5% from 1989 to 1998.[54] These observations indicated Triton was approaching an unusually warm southern hemisphere summer season that happens only once every few hundred years. Theories for this warming include a change of frost patterns on Triton's surface and a change in ice albedo, which would allow more heat to be absorbed.[55] Another theory argues that temperature changes are a result of the deposition of dark, red material from geological processes. Because Triton's Bond albedo is among the highest in the Solar System, it is sensitive to small variations in spectral albedo.[56]

## Surface features

Photomosaic of Triton's sub-Neptunian hemisphere. The bright, slightly pinkish, south polar cap at bottom is composed of nitrogen and methane ice and is streaked by dust deposits left by nitrogen gas geysers. The darker region above it includes Triton's "cantaloupe terrain" and cryovolcanic and tectonic features. Interpretative geomorphological map of Triton

All detailed knowledge of the surface of Triton was acquired from a distance of 40,000 km by the Voyager 2 spacecraft during a single encounter in 1989.[57] The 40% of Triton's surface imaged by Voyager 2 revealed blocky outcrops, ridges, troughs, furrows, hollows, plateaus, icy plains and a few craters. Triton is relatively flat; its observed topography never varies beyond a kilometer.[7] The impact craters observed are concentrated almost entirely in Triton's leading hemisphere.[58] Analysis of crater density and distribution has suggested that in geological terms, Triton's surface is extremely young, with regions varying from an estimated 50 million years old to just an estimated 6 million years old.[59] Fifty-five percent of Triton's surface is covered with frozen nitrogen, with water ice comprising 15–35% and frozen CO2 forming the remaining 10–20%.[60] The surface shows deposits of tholins, organic chemical compounds that may be precursors to the origin of life.[61]

### Cryovolcanism

Further information: Astronomy:Cryovolcano

One of the largest cryovolcanic features found on Triton is Leviathan Patera,[62] a caldera-like feature roughly 100 km in diameter seen near the equator. Surrounding this caldera is a volcanic dome that stretches for roughly 2,000 km along its longest axis, indicating that Leviathan is the second largest volcano in the solar system by area, after Alba Mons. This feature is also connected to two enormous cryolava lakes seen northwest of the caldera. Because the cryolava on Triton is believed to be primarily water ice with some ammonia, these lakes would qualify as stable bodies of surface liquid water while they were molten. This is the first place such bodies have been found apart from Earth, and Triton is the only icy body known to feature cryolava lakes, although similar cryomagmatic extrusions can be seen on Ariel, Ganymede, Charon, and Titan.[63]

The Voyager 2 probe in 1989 observed a handful of geyser-like eruptions of nitrogen gas and entrained dust from beneath the surface of Triton in plumes up to 8 km high.[34][64] Triton is thus, along with Earth, Io, Europa and Enceladus, one of the few bodies in the Solar System on which active eruptions of some sort have been observed.[65] The best-observed examples are named Hili and Mahilani (after a Zulu water sprite and a Tongan sea spirit, respectively).[66]

All the geysers observed were located between 50° and 57°S, the part of Triton's surface close to the subsolar point. This indicates that solar heating, although very weak at Triton's great distance from the Sun, plays a crucial role. It is thought that the surface of Triton probably consists of a translucent layer of frozen nitrogen overlying a darker substrate, which creates a kind of "solid greenhouse effect". Solar radiation passes through the thin surface ice sheet, slowly heating and vaporizing subsurface nitrogen until enough gas pressure accumulates for it to erupt through the crust.[7][51] A temperature increase of just 4 K above the ambient surface temperature of 37 K could drive eruptions to the heights observed.[64] Although commonly termed "cryovolcanic", this nitrogen plume activity is distinct from Triton's larger-scale cryovolcanic eruptions, as well as volcanic processes on other worlds, which are powered by internal heat. CO2 geysers on Mars are thought to erupt from its south polar cap each spring in the same way as Triton's geysers.[67]

Each eruption of a Triton geyser may last up to a year, driven by the sublimation of about 100 million m3 (3.5 billion cu ft) of nitrogen ice over this interval; dust entrained may be deposited up to 150 km downwind in visible streaks, and perhaps much farther in more diffuse deposits.[64] Voyager 2's images of Triton's southern hemisphere show many such streaks of dark material.[68] Between 1977 and the Voyager 2 flyby in 1989, Triton shifted from a reddish color, similar to Pluto, to a far paler hue, suggesting that lighter nitrogen frosts had covered older reddish material.[7] The eruption of volatiles from Triton's equator and their deposition at the poles may redistribute enough mass over 10,000 years to cause polar wander.[69]

* Close up of the volcanic province of Leviathan Patera, the caldera in the center of the image. Several pit chains extend radially from the caldera to the right of the image, while the smaller of the two cryolava lakes is seen to the upper left. Just off-screen to the lower left is a fault zone aligned radially with the caldera, indicating a close connection between the tectonics and volcanology of this geologic unit.

* Dark streaks across Triton's south polar cap surface, thought to be dust deposits left by eruptions of nitrogen geysers

* Two large cryolava lakes on Triton, seen west of Leviathan Patera. Combined, they are nearly the size of Kraken Mare on Titan. These features are unusually crater free, indicating they are young and were recently molten.

### Polar cap, plains and ridges

Triton's bright south polar cap above a region of cantaloupe terrain

Triton's south polar region is covered by a highly reflective cap of frozen nitrogen and methane sprinkled by impact craters and openings of geysers. Little is known about the north pole because it was on the night side during the Voyager 2 encounter, but it is thought that Triton must also have a north polar ice cap.[49]

The high plains found on Triton's eastern hemisphere, such as Cipango Planum, cover over and blot out older features, and are therefore almost certainly the result of icy lava washing over the previous landscape. The plains are dotted with pits, such as Leviathan Patera, which are probably the vents from which this lava emerged. The composition of the lava is unknown, although a mixture of ammonia and water is suspected.[7]

Four roughly circular "walled plains" have been identified on Triton. They are the flattest regions so far discovered, with a variance in altitude of less than 200 m. They are thought to have formed from the eruption of icy lava.[7] The plains near Triton's eastern limb are dotted with black spots, the maculae. Some maculae are simple dark spots with diffuse boundaries, and others comprise a dark central patch surrounded by a white halo with sharp boundaries. The maculae typically have diameters of about 100 km and widths of the halos of between 20 and 30 km.[7]

There are extensive ridges and valleys in complex patterns across Triton's surface, probably the result of freeze–thaw cycles.[70] Many also appear to be tectonic and may result from an extension or strike-slip faulting.[71] There are long double ridges of ice with central troughs bearing a strong resemblance to Europan lineae (although they have a larger scale[14]), and which may have a similar origin,[7] possibly shear heating from strike-slip motion along faults caused by diurnal tidal stresses experienced before Triton's orbit was fully circularized.[14] These faults with parallel ridges expelled from the interior cross complex terrain with valleys in the equatorial region. The ridges and furrows, or sulci, such as Yasu Sulci, Ho Sulci, and Lo Sulci,[72] are thought to be of intermediate age in Triton's geological history, and in many cases to have formed concurrently. They tend to be clustered in groups or "packets".[71]

### Cantaloupe terrain

Cantaloupe terrain viewed from 130,000 km by Voyager 2, with crosscutting Europa-like double ridges. Slidr Sulci (vertical) and Tano Sulci form the prominent "X".

Triton's western hemisphere consists of a strange series of fissures and depressions known as "cantaloupe terrain" because it resembles the skin of a cantaloupe melon. Although it has few craters, it is thought that this is the oldest terrain on Triton.[73] It probably covers much of Triton's western half.[7]

Cantaloupe terrain, which is mostly dirty water ice, is only known to exist on Triton. It contains depressions 30–40 km in diameter.[73] The depressions (cavi) are probably not impact craters because they are all of the similar size and have smooth curves. The leading hypothesis for their formation is diapirism, the rising of "lumps" of less dense material through a stratum of denser material.[7][74] Alternative hypotheses include formation by collapses, or by flooding caused by cryovolcanism.[73]

### Impact craters

Tuonela Planitia (left) and Ruach Planitia (center) are two of Triton's cryovolcanic "walled plains". The paucity of craters is evidence of extensive, relatively recent, geologic activity.

Due to constant erasure and modification by ongoing geological activity, impact craters on Triton's surface are relatively rare. A census of Triton's craters imaged by Voyager 2 found only 179 that were incontestably of impact origin, compared with 835 observed for Uranus's moon Miranda, which has only three percent of Triton's surface area.[75] The largest crater observed on Triton thought to have been created by an impact is a 27-kilometer-diameter (17 mi) feature called Mazomba.[75][76] Although larger craters have been observed, they are generally thought to be volcanic.[75]

The few impact craters on Triton are almost all concentrated in the leading hemisphere—that facing the direction of the orbital motion—with the majority concentrated around the equator between 30° and 70° longitude,[75] resulting from material swept up from orbit around Neptune.[59] Because it orbits with one side permanently facing the planet, astronomers expect that Triton should have fewer impacts on its trailing hemisphere, due to impacts on the leading hemisphere being more frequent and more violent.[75] Voyager 2 imaged only 40% of Triton's surface, so this remains uncertain. However, the observed cratering asymmetry exceeds what can be explained based on the impactor populations, and implies a younger surface age for the crater-free regions (≤ 6 million years old) than for the cratered regions (≤ 50 million years old).[58]

## Observation and exploration

NASA illustration detailing the studies of the proposed Trident mission Neptune (top) and Triton (bottom) three days after flyby of Voyager 2

The orbital properties of Triton were already determined with high accuracy in the 19th century. It was found to have a retrograde orbit, at a very high angle of inclination to the plane of Neptune's orbit. The first detailed observations of Triton were not made until 1930. Little was known about the satellite until Voyager 2 flew by in 1989.[7]

Before the flyby of Voyager 2, astronomers suspected that Triton might have liquid nitrogen seas and a nitrogen/methane atmosphere with a density as much as 30% that of Earth. Like the famous overestimates of the atmospheric density of Mars, this proved incorrect. As with Mars, a denser atmosphere is postulated for its early history.[77]

The first attempt to measure the diameter of Triton was made by Gerard Kuiper in 1954. He obtained a value of 3,800 km. Subsequent measurement attempts arrived at values ranging from 2,500 to 6,000 km, or from slightly smaller than the Moon (3,474.2 km) to nearly half the diameter of Earth.[78] Data from the approach of Voyager 2 to Neptune on August 25, 1989, led to a more accurate estimate of Triton's diameter (2,706 km).[79]

In the 1990s, various observations from Earth were made of the limb of Triton using the occultation of nearby stars, which indicated the presence of an atmosphere and an exotic surface. Observations in late 1997 suggest that Triton is heating up and the atmosphere has become significantly denser since Voyager 2 flew past in 1989.[53]

New concepts for missions to the Neptune system to be conducted in the 2010s were proposed by NASA scientists on numerous occasions over the last decades. All of them identified Triton as being a prime target and a separate Triton lander comparable to the Huygens probe for Titan was frequently included in those plans. No efforts aimed at Neptune and Triton went beyond the proposal phase and NASA's funding for missions to the outer Solar System is currently focused on the Jupiter and Saturn systems.[80] A proposed lander mission to Triton, called Triton Hopper, would mine nitrogen ice from the surface of Triton and process it to be used as a propellant for a small rocket, enabling it to fly or 'hop' across the surface.[81][82] Another concept, involving a flyby, was formally proposed in 2019 as part of NASA's Discovery Program under the name Trident.[83] Neptune Odyssey is a mission concept for a Neptune orbiter with a focus on Triton being studied beginning April 2021 as a possible large strategic science mission by NASA that would launch in 2033 and arrive at the Neptune system in 2049.[84] Two lower-cost versions intended for the New Frontiers program were then proposed, the first the following June, and the second in 2023. The first is Triton Ocean World Surveyor, scheduled for launch in 2031 and arriving in 2047,[85] and the second is Nautilus, launching in August 2042 and arriving in April 2057.[86][17]

TOWS and Nautilus instrument comparison (not to scale)

## Maps

Enhanced-color map; leading hemisphere is on right

Enhanced-color polar maps; south is right

|

## See also

* List of natural satellites
* List of geological features on Triton
* Neptune in fiction
* Triton Hopper, a proposed lander to Triton
* Triton's sky
* Shensuo, a proposed mission that would flyby Triton

## Notes

1. ↑ Calculated on the basis of other parameters.
2. ↑ Surface area derived from the radius r: 4πr2.
3. ↑ Volume v derived from the radius r: 43πr3.
4. ↑ Mass m derived from the density d and the volume v: m=d×v.
5. ↑ Surface gravity derived from the mass m, the gravitational constant G and the radius r: Gmr2.
6. ↑ Escape velocity derived from the mass m, the gravitational constant G and the radius r: 2Gm/r.
7. ↑ With respect to Triton's orbit about Neptune.
8. ↑ Lassell rejected his previous claim of discovery when he found that the orientation of the supposed rings changed when he rotated his telescope tube; see p. 9 of Smith & Baum, 1984.[20]
9. ↑ Largest irregular moons: Saturn's Phoebe (210 km), Uranus's Sycorax (160 km), and Jupiter's Himalia (140 km)
10. ↑ Mass of Triton: 2.14×1022 kg. Combined mass of 12 other known moons of Neptune: 7.53×1019 kg, or 0.35%. The mass of the rings is negligible.
11. ↑ The masses of other spherical moons are: Titania—3.5×1021, Oberon—3.0×1021, Rhea—2.3×1021, Iapetus—1.8×1021, Charon—1.5×1021, Ariel—1.3×1021, Umbriel—1.2×1021, Dione—1.0×1021, Tethys—0.6×1021, Enceladus—0.12×1021, Miranda—0.06×1021, Proteus—0.05×1021, Mimas—0.04×1021. The total mass of remaining moons is about 0.09×1021. So, the total mass of all moons smaller than Triton is about 1.65×1022. (See List of moons by diameter)

## References

1. ↑ Robert Graves (1945) Hercules, My Shipmate
2. ↑ 2.0 2.1 Williams, David R. (November 23, 2006). "Neptunian Satellite Fact Sheet". NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptuniansatfact.html.
3. ↑ 3.0 3.1 Overbye, Dennis (November 5, 2014). "Bound for Pluto, Carrying Memories of Triton". New York Times. https://www.nytimes.com/2014/11/05/science/bound-for-pluto-carrying-memories-of-triton.html.
4. ↑ 4.0 4.1 4.2 4.3 4.4 Jacobson, R. A. — AJ (April 3, 2009). "Planetary Satellite Mean Orbital Parameters". JPL satellite ephemeris. JPL (Solar System Dynamics). http://ssd.jpl.nasa.gov/?sat_elem.
5. ↑ 5.0 5.1 5.2 5.3 5.4 Jacobson, R. A. (3 April 2009). "The Orbits of the Neptunian Satellites and the Orientation of the Pole of Neptune". The Astronomical Journal 137 (5): 4322–4329. doi:10.1088/0004-6256/137/5/4322. Bibcode: 2009AJ....137.4322J.
6. ↑ 6.0 6.1 6.2 6.3 6.4 "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). http://ssd.jpl.nasa.gov/?sat_phys_par.
7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 7.12 7.13 7.14 7.15 7.16 7.17 7.18 7.19 7.20 7.21 7.22 7.23 McKinnon, William B.; Kirk, Randolph L. (2014). "Encyclopedia of the Solar System". in Tilman Spohn. Encyclopedia of the Solar System (3rd ed.). Amsterdam; Boston: Elsevier. pp. 861–882. ISBN 978-0-12-416034-7. https://books.google.com/books?id=0bEMAwAAQBAJ&pg=PA861.
8. ↑ "Classic Satellites of the Solar System". Observatorio ARVAL. http://www.oarval.org/ClasSaten.htm.
9. ↑ Fischer, Daniel (February 12, 2006). "Kuiperoids & Scattered Objects". Argelander-Institut für Astronomie. http://www.astro.uni-bonn.de/~dfischer/planeten/jwd.html.
10. ↑ 10.0 10.1 10.2 Broadfoot, A. L.; Atreya, S. K.; Bertaux, J. L.; Blamont, J. E.; Dessler, A. J.; Donahue, T. M.; Forrester, W. T.; Hall, D. T. et al. (1989). "Ultraviolet Spectrometer Observations of Neptune and Triton". Science 246 (4936): 1459–66. doi:10.1126/science.246.4936.1459. PMID 17756000. Bibcode: 1989Sci...246.1459B.
11. ↑ "Neptune: Moons: Triton". NASA. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Triton.
12. ↑ Chang, Kenneth (18 October 2014). "Dark Spots in Our Knowledge of Neptune". New York Times. https://www.nytimes.com/2014/08/19/science/dark-spots-in-our-knowledge-of-neptune.html.
13. ↑ 13.0 13.1 13.2 13.3 Agnor, C. B.; Hamilton, D. P. (2006). "Neptune's capture of its moon Triton in a binary–planet gravitational encounter". Nature 441 (7090): 192–4. doi:10.1038/nature04792. PMID 16688170. Bibcode: 2006Natur.441..192A. http://extranet.on.br/rodney/curso2010/aula9/tritoncapt_hamilton.pdf. Retrieved August 28, 2015.
14. ↑ 14.0 14.1 14.2 Prockter, L. M.; Nimmo, F.; Pappalardo, R. T. (July 30, 2005). "A shear heating origin for ridges on Triton". Geophysical Research Letters 32 (14): L14202. doi:10.1029/2005GL022832. Bibcode: 2005GeoRL..3214202P. http://www.es.ucsc.edu/~fnimmo/website/Prockter_et_al.pdf. Retrieved October 9, 2011.
15. ↑ "In Depth | Triton". https://solarsystem.nasa.gov/moons/neptune-moons/triton/in-depth. "NASA's Voyager 2―the only spacecraft to fly past Neptune and Triton―found surface temperatures of −391 degrees Fahrenheit (−235 degrees Celsius). During its 1989 flyby, Voyager 2 also found Triton has active geysers, making it one of the few geologically active moons in our solar system."
16. ↑ "NASA Selects Four Possible Missions to Study the Secrets of the Solar System". https://www.jpl.nasa.gov/news/nasa-selects-four-possible-missions-to-study-the-secrets-of-the-solar-system.
17. ↑ 17.0 17.1 "Planetary Science Summer School · Jason Dekarske". December 19, 2023. https://www.jasondekarske.com/research/psss/.
18. ↑ 18.0 18.1 Lassell, William (November 12, 1847). "Lassell's Satellite of Neptune". Monthly Notices of the Royal Astronomical Society 10 (1): 8. doi:10.1093/mnras/10.1.8. Bibcode: 1847MNRAS...8....9B. https://zenodo.org/record/1431823.
19. ↑ Lassell, William (November 13, 1846). "Discovery of Supposed Ring and Satellite of Neptune". Monthly Notices of the Royal Astronomical Society 7 (9): 157. doi:10.1093/mnras/7.9.154. Bibcode: 1846MNRAS...7..157L.
Lassell, William (December 11, 1846). "Physical observations on Neptune". Monthly Notices of the Royal Astronomical Society 7 (10): 167–168. doi:10.1093/mnras/7.10.165a. Bibcode: 1847MNRAS...7..297L.
Lassell, W. (1847). "Observations of Neptune and his satellite". Monthly Notices of the Royal Astronomical Society 7 (17): 307–308. doi:10.1002/asna.18530360703. Bibcode: 1847MNRAS...7..307L. https://zenodo.org/record/1424639.
20. ↑ 20.0 20.1 Smith, R. W.; Baum, R. (1984). "William Lassell and the Ring of Neptune: A Case Study in Instrumental Failure". Journal for the History of Astronomy 15 (42): 1–17. doi:10.1177/002182868401500101. Bibcode: 1984JHA....15....1S.
21. ↑ 21.0 21.1 "The Royal Observatory Greenwich – where east meets west: Telescope: The Lassell 2-foot Reflector (1847)". http://www.royalobservatorygreenwich.org/articles.php?article=1046.
22. ↑ Flammarion, Camille (1880). Astronomie populaire. p. 591. http://gallica.bnf.fr/ark:/12148/bpt6k94887w/f610.table. Retrieved April 10, 2007.
23. ↑ Moore, Patrick (April 1996). The planet Neptune: an historical survey before Voyager. Wiley-Praxis Series in Astronomy and Astrophysics (2nd ed.). John Wiley & Sons. pp. 150 (see p. 68). ISBN 978-0-471-96015-7. OCLC 33103787. https://books.google.com/books?id=RZruAAAAMAAJ&q=H.+N.+Russell.
24. ↑ "Planet and Satellite Names and their Discoverers". International Astronomical Union. http://www.indwes.edu/Faculty/bcupp/solarsys/Names.htm.
25. ↑ Davies, M.; Rogers, P.; Colvin, T. (1991). "A Control Network of Triton". J. Geophys. Res. 96(E1) (E1): 15675–15681. doi:10.1029/91JE00976. Bibcode: 1991JGR....9615675D. https://www.rand.org/content/dam/rand/pubs/notes/2009/N3425.pdf.
26. ↑ Seasons Discovered on Neptune's Moon Triton — Space.com (2010)
27. ↑ 27.0 27.1 Chyba, C. F.; Jankowski, D. G.; Nicholson, P. D. (July 1989). "Tidal evolution in the Neptune-Triton system". Astronomy and Astrophysics 219 (1–2): L23–L26. Bibcode: 1989A&A...219L..23C.
28. ↑ 28.0 28.1 Cruikshank, Dale P. (2004). "Triton, Pluto, Centaurs, and Trans-Neptunian Bodies". Space Science Reviews 116 (1–2): 421–439. doi:10.1007/s11214-005-1964-0. ISBN 978-1-4020-3362-9. Bibcode: 2005SSRv..116..421C. https://books.google.com/books?id=MbmiTd3x1UcC&q=Triton,+Pluto,+Centaurs,+and+Trans-Neptunian+Bodies&pg=PA421.
29. ↑ Ross, MN; Schubert, G (September 1990). "The coupled orbital and thermal evolution of Triton". Geophysical Research Letters 17 (10): 1749–1752. doi:10.1029/GL017i010p01749. Bibcode: 1990GeoRL..17.1749R.
30. ↑ Sheppard, Scott S.; Jewitt, David (2004). "Extreme Kuiper Belt Object 2001 QG298 and the Fraction of Contact Binaries". The Astronomical Journal 127 (5): 3023–3033. doi:10.1086/383558. ISSN 0004-6256. Bibcode: 2004AJ....127.3023S.
31. ↑ Jewitt, Dave (2005). "Binary Kuiper Belt Objects". University of Hawaii. http://www2.ess.ucla.edu/~jewitt/kb/binaries.html.
32. ↑ Raluca Rufu and Robin Canup (Nov 5, 2017). "Triton's evolution with a primordial Neptunian satellite system". The Astronomical Journal 154 (5): 208. doi:10.3847/1538-3881/aa9184. PMID 31019331. Bibcode: 2017AJ....154..208R.
33. ↑ "Triton crashed into Neptune's moons". New Scientist 236 (3152): 16. Nov 18, 2017. doi:10.1016/S0262-4079(17)32247-9. Bibcode: 2017NewSc.236...16.. https://www.newscientist.com/article/mg23631521-900-neptunes-other-moons-were-normal-until-triton-crashed-the-party.
34. ↑ 34.0 34.1 "Triton (Voyager)". NASA. June 1, 2005. http://voyager.jpl.nasa.gov/science/neptune_triton.html.
35. ↑ Ruiz, Javier (December 2003). "Heat flow and depth to a possible internal ocean on Triton". Icarus 166 (2): 436–439. doi:10.1016/j.icarus.2003.09.009. Bibcode: 2003Icar..166..436R. http://eprints.ucm.es/10454/1/11-Tritón_1.pdf. Retrieved June 25, 2019.
36. ↑ Medkeff, Jeff (2002). "Lunar Albedo". Sky and Telescope Magazine. http://jeff.medkeff.com/astro/lunar/obs_tech/albedo.htm.
37. ↑ https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Astronomy_1e_(OpenStax)/12:_Rings_Moons_and_Pluto/12.03:_Titan_and_Triton
38. ↑ https://sos.noaa.gov/catalog/datasets/triton-neptunes-moon/
39. ↑ https://science.nasa.gov/neptune/moons/triton/#hds-sidebar-nav-1
40. ↑ Nelson, R.M.; Smythe, W.D.; Wallis, B.D.; Horn, L.J. et al. (1990). "Temperature and Thermal Emissivity of the Surface of Neptune's Satellite Triton". Science 250 (4979): 429–31. doi:10.1126/science.250.4979.429. PMID 17793020. Bibcode: 1990Sci...250..429N.
41. ↑ Grundy, W. M.; Buie, M. W.; Spencer, J. R. (October 2002). "Spectroscopy of Pluto and Triton at 3–4 Microns: Possible Evidence for Wide Distribution of Nonvolatile Solids". The Astronomical Journal 124 (4): 2273–2278. doi:10.1086/342933. Bibcode: 2002AJ....124.2273G. http://pdfs.semanticscholar.org/0c69/02d4e8fe0c7e4e708097cd5b125e479e87d7.pdf.
42. ↑ Hussmann, Hauke; Sohl, Frank; Spohn, Tilman (November 2006). "Subsurface oceans and deep interiors of medium-sized outer planet satellites and large trans-neptunian objects". Icarus 185 (1): 258–273. doi:10.1016/j.icarus.2006.06.005. Bibcode: 2006Icar..185..258H. https://www.researchgate.net/publication/225019299.
43. ↑ 43.0 43.1 43.2 Wenz, John (4 October 2017). "Overlooked Ocean Worlds Fill the Outer Solar System". Scientific American. https://www.scientificamerican.com/article/overlooked-ocean-worlds-fill-the-outer-solar-system/.
44. ↑ 44.0 44.1 Nimmo, Francis (15 January 2015). "Powering Triton's recent geological activity by obliquity tides: Implications for Pluto geology". Icarus 246: 2–10. doi:10.1016/j.icarus.2014.01.044. Bibcode: 2015Icar..246....2N. https://escholarship.org/content/qt99s8t6zm/qt99s8t6zm.pdf?t=nnm476.
45. ↑ Irwin, L. N.; Schulze-Makuch, D. (2001). "Assessing the Plausibility of Life on Other Worlds". Astrobiology 1 (2): 143–60. doi:10.1089/153110701753198918. PMID 12467118. Bibcode: 2001AsBio...1..143I.
46. ↑ Doyle, Amanda (September 6, 2012). "Does Neptune's moon Triton have a subsurface ocean?". Space.com. http://www.space.com/17470-neptune-moon-triton-subsurface-ocean.html.
47. ↑ Miller, Ron; Hartmann, William K. (May 2005). The Grand Tour: A Traveler's Guide to the Solar System (3rd ed.). Thailand: Workman Publishing. pp. 172–73. ISBN 978-0-7611-3547-0.
48. ↑ Lellouch, E.; de Bergh, C.; Sicardy, B.; Ferron, S.; Käufl, H.-U. (2010). "Detection of CO in Triton's atmosphere and the nature of surface-atmosphere interactions". Astronomy & Astrophysics 512: L8. doi:10.1051/0004-6361/201014339. Bibcode: 2010A&A...512L...8L.
49. ↑ 49.0 49.1 Duxbury, N S; Brown, R H (August 1993). "The Phase Composition of Triton's Polar Caps". Science 261 (5122): 748–751. doi:10.1126/science.261.5122.748. PMID 17757213. Bibcode: 1993Sci...261..748D.
50. ↑ Tryka, K. A.; Brown, R. H.; Anicich, V.; Cruikshank, D. P.; Owen, T. C. (1993). "Spectroscopic Determination of the Phase Composition and Temperature of Nitrogen Ice on Triton". Science 261 (5122): 751–4. doi:10.1126/science.261.5122.751. PMID 17757214. Bibcode: 1993Sci...261..751T.
51. ↑ 51.0 51.1 Smith, B. A.; Soderblom, L. A.; Banfield, D.; Barnet, C.; Basilevsky, A. T.; Beebe, R. F.; Bollinger, K.; Boyce, J. M. et al. (1989). "Voyager 2 at Neptune: Imaging Science Results". Science 246 (4936): 1422–1449. doi:10.1126/science.246.4936.1422. PMID 17755997. Bibcode: 1989Sci...246.1422S. https://zenodo.org/record/1230992.
52. ↑ Stevens, M. H.; Strobel, D. F.; Summers, M. E.; Yelle, R. V. (April 3, 1992). "On the thermal structure of Triton's thermosphere". Geophysical Research Letters 19 (7): 669–672. doi:10.1029/92GL00651. Bibcode: 1992GeoRL..19..669S. http://www.agu.org/pubs/crossref/1992/92GL00651.shtml. Retrieved October 8, 2011.
53. ↑ 53.0 53.1 Savage, D.; Weaver, D.; Halber, D. (June 24, 1998). "Hubble Space Telescope Helps Find Evidence that Neptune's Largest Moon Is Warming Up". Hubblesite. STScI-1998-23. http://hubblesite.org/newscenter/newsdesk/archive/releases/1998/23/text/. Retrieved December 31, 2007.
54. ↑ "MIT researcher finds evidence of global warming on Neptune's largest moon". Massachusetts Institute of Technology. June 24, 1998. http://web.mit.edu/newsoffice/1998/triton.html.
55. ↑ MacGrath, Melissa (June 28, 1998). "Solar System Satellites and Summary". Hubble's Science Legacy: Future Optical/Ultraviolet Astronomy from Space (Space Telescope Science Institute) 291: 93. Bibcode: 2003ASPC..291...93M.
56. ↑ Buratti, Bonnie J.; Hicks, Michael D.; Newburn, Ray L. Jr. (January 21, 1999). "Does global warming make Triton blush?". Nature 397 (6716): 219–20. doi:10.1038/16615. PMID 9930696. Bibcode: 1999Natur.397..219B.
57. ↑ Gray, D (1989). "Voyager 2 Neptune navigation results". Astrodynamics Conference: 108. doi:10.2514/6.1990-2876.
58. ↑ 58.0 58.1 Mah, J.; Brasser, R. (2019). "The origin of the cratering asymmetry on Triton". Monthly Notices of the Royal Astronomical Society 486: 836–842. doi:10.1093/mnras/stz851.
59. ↑ 59.0 59.1 Schenk, Paul M.; Zahnle, Kevin (December 2007). "On the negligible surface age of Triton". Icarus 192 (1): 135–49. doi:10.1016/j.icarus.2007.07.004. Bibcode: 2007Icar..192..135S.
60. ↑ Williams, Matt (28 July 2015). "Neptune's Moon Triton". Universe Today. https://www.universetoday.com/56042/triton/.
61. ↑ Oleson, Steven R.; Landis, Geoffrey. "Triton Hopper: Exploring Neptune's Captured Kuiper Belt Object". Planetary Science Vision 2050 Workshop 2017. https://www.hou.usra.edu/meetings/V2050/pdf/8145.pdf.
62. ↑ Martin-Herrero, Alvaro; Romeo, Ignacio; Ruiz, Javier (2018). "Heat flow in Triton: Implications for heat sources powering recent geologic activity". Planetary and Space Science 160: 19–25. doi:10.1016/j.pss.2018.03.010. Bibcode: 2018P&SS..160...19M.
63. ↑ Schenk, Paul; Prockter, Louise. "Candidate Cryovolcanic Features in the Outer Solar System". Lunar and Planetary Institute. https://www.hou.usra.edu/meetings/cryovolcanism2018/pdf/2035.pdf.
64. ↑ 64.0 64.1 64.2 Soderblom, L. A.; Kieffer, S. W.; Becker, T. L.; Brown, R. H.; Cook, A. F. II; Hansen, C. J.; Johnson, T. V.; Kirk, R. L. (October 19, 1990). "Triton's Geyser-Like Plumes: Discovery and Basic Characterization". Science 250 (4979): 410–415. doi:10.1126/science.250.4979.410. PMID 17793016. Bibcode: 1990Sci...250..410S. https://www.geology.illinois.edu/~skieffer/papers/Truiton_Science_1990.pdf.
65. ↑ Kargel, JS (1994). "Cryovolcanism on the icy satellites". Earth, Moon, and Planets 67 (1–3): 101–113. 1995. doi:10.1007/BF00613296. Bibcode: 1995EM&P...67..101K. https://zenodo.org/record/1232444.
66. ↑ USGS Astrogeology Research Program: Gazetteer of Planetary Nomenclature, search for "Hili" and "Mahilani"
67. ↑ Burnham, Robert (August 16, 2006). "Gas jet plumes unveil mystery of 'spiders' on Mars". Arizona State University. http://www.asu.edu/news/stories/200608/20060818_marsplumes.htm.
68. ↑ Kirk, R. L. (1990). "Thermal Models of Insolation-Driven Nitrogen Geysers on Triton". LPSC XXI. 21. Lunar and Planetary Institute. 633–634. Bibcode: 1990LPI....21..633K.
69. ↑ Rubincam, David Parry (2002). "Polar wander on Triton and Pluto due to volatile migration". Icarus 163 (2): 63–71. doi:10.1016/S0019-1035(03)00080-0. Bibcode: 2003Icar..163..469R.
70. ↑ Elliot, J. L.; Hammel, H. B.; Wasserman, L. H.; Franz, O. G.; McDonald, S. W.; Person, M. J.; Olkin, C. B.; Dunham, E. W. et al. (1998). "Global warming on Triton". Nature 393 (6687): 765–767. doi:10.1038/31651. Bibcode: 1998Natur.393..765E.
71. ↑ 71.0 71.1 Collins, Geoffrey; Schenk, Paul (March 14–18, 1994). "Triton's Lineaments: Complex Morphology and Stress Patterns". Abstracts of the 25th Lunar and Planetary Science Conference. 25. Houston, TX. 277. Bibcode: 1994LPI....25..277C.
72. ↑ Aksnes, K; Brahic, A; Fulchignoni, M; Marov, M Ya (1990). "Working Group for Planetary System Nomenclature". Reports on Astronomy (State University of New York) 21A: 613–19. 1991. 1991IAUTA..21..613A. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940014368_1994014368.pdf. Retrieved January 25, 2008.
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74. ↑ Schenk, P.; Jackson, M. P. A. (April 1993). "Diapirism on Triton: A record of crustal layering and instability". Geology 21 (4): 299–302. doi:10.1130/0091-7613(1993)021<0299:DOTARO>2.3.CO;2. Bibcode: 1993Geo....21..299S.
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## External links

* Triton profile at NASA's Solar System Exploration site
* Triton page at The Nine Planets
* Triton page (including labelled Triton map) at Views of the Solar System
* Triton map from Paul Schenk, Lunar and Planetary Institute
* Triton images from the NASA/JPL Photojournal
* Triton nomenclature from the USGS Planetary Nomenclature website

* v
* t
* e

Moons of Neptune

Generally listed in increasing distance from Neptune

Regular (inner)|

* Naiad
* Thalassa
* Despina
* Galatea
* Larissa
* Hippocamp
* Proteus

Triton|

* Triton (Atmosphere
* Geological features
* Sky)

Irregular|

* Nereid
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* Sao
* Laomedeia
* Psamathe
* Neso

See also|

* Neptune trojans
* Rings of Neptune

* Book
* Category
* Portal

* v
* t
* e

Neptune

* Outline of Neptune

Geography|

* Great Dark Spot
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NASA image of Neptune

Moons|

* Despina
* Galatea
* Halimede
* Hippocamp
* Laomedeia
* Larissa
* Naiad
* Nereid
* Neso
* Proteus
* Psamathe
* Sao
* Thalassa
* Triton

Astronomy|

| Discovery|

* Urbain Le Verrier
* Johann Gottfried Galle
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* William Lassell

|

General|

* Kuiper belt
* Neptune-crossing minor planets

Trojans|

* 2001 QR322
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* 2004 UP10
* 2005 TN53
* 2005 TO74
* 2006 RJ103
* (527604) 2007 VL305
* 2008 LC18
* 2011 HM102

Exploration|

| Past|

* Voyager 2 (1989 flyby)

|

Proposals|

* ODINUS
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Cancelled|

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Related|

* Fiction
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Natural satellites of the Solar System

Planetary
satellites|

* Terrestrial
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Dwarf-planet
satellites|

* Plutonian
* Haumean
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* OR10
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Minor-planet moons|

* Main belt binaries:
* Antiope
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* Tokai
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* Trojans:
* Patroclus–Menoetius
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* TNOs:
* Huya
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* 2002 UX25
* Logos–Zoe
* Ceto–Phorcys
* Borasisi–Pabu
* Sila–Nunam
* Teharonhiawako–Sawiskera
* Salacia–Actaea
* 2002 WC19
* Altjira
* Varda–Ilmarë
* 2003 AZ84
* Gǃkúnǁʼhòmdímà–Gǃòʼé ǃHú
* Mors–Somnus
* Manwë–Thorondor
* ǂKá̦gára–ǃHãunu
* 2013 FY27

Ranked by size|

* Planetary-mass moon
* Ganymede
* largest: 5268 km / 0.413 Earths
* Titan
* Callisto
* Io
* Moon
* Europa
* Triton
* Titania
* Rhea
* Oberon
* Iapetus
* Charon
* Umbriel
* Ariel
* Dione
* Tethys
* Dysnomia
* Enceladus
* Miranda
* Vanth
* Proteus
* Mimas
* Ilmarë
* Nereid
* Hiʻiaka
* Actaea
* Hyperion
* ...

* Discovery timeline
* Inner moons
* Irregular moons
* List
* Planetary-mass moons
* Naming
* Subsatellite
* Regular moons
* Trojan moons

* v
* t
* e

Dwarf planets

* List of possible dwarf planets
* Former dwarf planets
* Phoebe
* Triton
* Vesta
* Mesoplanet
* Planemo

Asteroid belt|

| IAU|

* Ceres

|

Possible|

* Hygiea
* Interamnia

Centaurs|

| Possible|

* Ceto
* Chariklo
* Chiron
* 1995 SN55
* 2010 TY53

|

Plutinos|

| IAU|

* Pluto

|

Possible|

* Huya
* Ixion
* Orcus
* 2001 QF298
* 2002 VR128
* 2002 XV93
* 2003 AZ84
* 2003 UZ413
* 2003 VS2
* 2007 JH43

Twotinos|

| Possible|

* 2002 WC19

|

Cubewanos|

| IAU|

* Makemake

|

Possible|

* Altjira
* Chaos
* Praamzius
* Quaoar
* Rhadamanthus
* Salacia
* Sila–Nunam
* Varda
* Varuna
* 1998 SN165
* 2002 AW197
* 2002 CY248
* 2002 KX14
* 2002 MS4
* 2002 TX300
* 2002 UX25
* 2003 OP32
* 2003 QW90
* 2004 GV9
* 2004 NT33
* 2004 PF115
* 2004 TY364
* 2004 UX10
* 2005 RN43
* 2005 RR43
* 2005 UQ513
* 2007 JJ43
* 2010 FX86
* 2010 VR11

Scattered disc|

| IAU|

* Eris

|

Possible|

* Dziewanna
* Gǃkúnǁʼhòmdímà
* 1996 GQ21
* 1996 TL66
* 1999 CC158
* 2001 UR163
* 2002 TC302
* 2004 XA192
* 2005 QU182
* 2005 RM43
* 2006 QH181
* 2007 OR10
* 2008 OG19
* 2010 KZ39
* 2010 RE64
* 2010 RF43
* 2010 TJ
* 2010 VZ98
* 2012 HH2
* 2013 FY27
* 2018 VG18

Detached objects|

| Possible|

* 1995 TL8
* 2000 CR105
* 2003 FY128
* 2003 QX113
* 2004 VN112
* 2004 XR190
* 2005 TB190
* 2008 ST291
* 2010 GB174

|

Sednoids|

| Possible|

* Sedna
* 2015 TG387
* 2012 VP113

|

Other / unknown
resonances|

| IAU|

* Haumea

|

Possible|

* FarFarOut
* V774104
* 1999 CD158
* 1999 DE9
* 1999 KR16
* 2000 YW134
* 2001 YH140
* 2002 XW93
* 2010 VK201
* 2011 FW62
* 2011 GM27
* 2013 FZ27
* 2014 UM33

* Category

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Original source: https://en.wikipedia.org/wiki/Triton (moon). Read more

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