Ice giant

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Uranus Voyager2 color calibrated.png
Uranus photographed by Voyager 2 in January 1986
Neptune Voyager2 color calibrated.png
Neptune photographed by Voyager 2 in August 1989

An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur. There are two ice giants in the Solar System: Uranus and Neptune.

Contents

In astrophysics and planetary science the term "ice" refers to volatile chemical compounds with freezing points above about 100  K, such as water, ammonia, or methane, with freezing points of 273 K (0°C), 195 K (−78°C), and 91 K (−182°C), respectively (see Volatiles). In the 1990s, it was determined that Uranus and Neptune were a distinct class of giant planet, separate from the other giant planets, Jupiter and Saturn, which are gas giants predominantly composed of hydrogen and helium. [1]

As such, Neptune and Uranus are now referred to as ice giants. Lacking well-defined solid surfaces, they are primarily composed of gases and liquids. Their constituent compounds were solids when they were primarily incorporated into the planets during their formation, either directly in the form of ice or trapped in water ice. Today, very little of the water in Uranus and Neptune remains in the form of ice. Instead, water primarily exists as supercritical fluid at the temperatures and pressures within them. [2] Uranus and Neptune consist of only about 20% hydrogen and helium by mass, compared to the Solar System's gas giants, Jupiter and Saturn, which are more than 90% hydrogen and helium by mass.

Terminology

In 1952, science fiction writer James Blish coined the term gas giant [3] and it was used to refer to the large non-terrestrial planets of the Solar System. However, since the late 1940s [4] the compositions of Uranus and Neptune have been understood to be significantly different from those of Jupiter and Saturn. They are primarily composed of elements heavier than hydrogen and helium, forming a separate type of giant planet altogether. Because during their formation Uranus and Neptune incorporated their material as either ice or gas trapped in water ice, the term ice giant came into use. [2] [4] In the early 1970s, the terminology became popular in the science fiction community, e.g., Bova (1971), [5] but the earliest scientific usage of the terminology was likely by Dunne & Burgess (1978) [6] in a NASA report. [7]

Formation

Modelling the formation of terrestrial and gas giants is relatively straightforward and uncontroversial. The terrestrial planets of the Solar System are widely understood to have formed through collisional accumulation of planetesimals within the protoplanetary disk. The gas giants—Jupiter, Saturn, and their extrasolar counterpart planets—are thought to have formed solid cores of around 10 Earth masses (MEarth) through the same process, while accreting gaseous envelopes from the surrounding solar nebula over the course of a few to several million years (Ma), [8] [9] although alternative models of core formation based on pebble accretion have recently been proposed. [10] Some extrasolar giant planets may instead have formed via gravitational disk instabilities. [9] [11]

The formation of Uranus and Neptune through a similar process of core accretion is far more problematic. The escape velocity for the small protoplanets about 20 astronomical units (AU) from the center of the Solar System would have been comparable to their relative velocities. Such bodies crossing the orbits of Saturn or Jupiter would have been liable to be sent on hyperbolic trajectories ejecting them from the system. Such bodies, being swept up by the gas giants, would also have been likely to just be accreted into larger planets or thrown into cometary orbits. [11]

Despite the trouble modelling their formation, many ice giant candidates have been observed orbiting other stars since 2004. This indicates that they may be common in the Milky Way. [2]

Migration

Considering the orbital challenges of protoplanets 20 AU or more from the centre of the Solar System would experience, a simple solution is that the ice giants formed between the orbits of Jupiter and Saturn before being gravitationally scattered outward to their now more distant orbits. [11]

Disk instability

Gravitational instability of the protoplanetary disk could also produce several gas giant protoplanets out to distances of up to 30 AU. Regions of slightly higher density in the disk could lead to the formation of clumps that eventually collapse to planetary densities. [11] A disk with even marginal gravitational instability could yield protoplanets between 10 and 30 AU in over one thousand years (ka). This is much shorter than the 100,000 to 1,000,000 years required to produce protoplanets through core accretion of the cloud and could make it viable in even the shortest-lived disks, which exist for only a few million years. [11]

A problem with this model is determining what kept the disk stable before the instability. There are several possible mechanisms allowing gravitational instability to occur during disk evolution. A close encounter with another protostar could provide a gravitational kick to an otherwise stable disk. A disk evolving magnetically is likely to have magnetic dead zones, due to varying degrees of ionization, where mass moved by magnetic forces could pile up, eventually becoming marginally gravitationally unstable. A protoplanetary disk may simply accrete matter slowly, causing relatively short periods of marginal gravitational instability and bursts of mass collection, followed by periods where the surface density drops below what is required to sustain the instability. [11]

Photoevaporation

Observations of photoevaporation of protoplanetary disks in the Orion Trapezium Cluster by extreme ultraviolet (EUV) radiation emitted by θ1 Orionis C suggests another possible mechanism for the formation of ice giants. Multiple-Jupiter-mass gas-giant protoplanets could have rapidly formed due to disk instability before having most of their hydrogen envelopes stripped off by intense EUV radiation from a nearby massive star. [11]

In the Carina Nebula, EUV fluxes are approximately 100 times higher than in Trapezium's Orion Nebula. Protoplanetary disks are present in both nebulae. Higher EUV fluxes make this an even more likely possibility for ice-giant formation. The stronger EUV would increase the removal of the gas envelopes from protoplanets before they could collapse sufficiently to resist further loss. [11]

Characteristics

These cut-aways illustrate interior models of the giant planets. The planetary cores of gas giants Jupiter and Saturn are overlaid by a deep layer of metallic hydrogen, whereas the mantles of the ice giants Uranus and Neptune are composed of heavier elements. Gas Giant Interiors.jpg
These cut-aways illustrate interior models of the giant planets. The planetary cores of gas giants Jupiter and Saturn are overlaid by a deep layer of metallic hydrogen, whereas the mantles of the ice giants Uranus and Neptune are composed of heavier elements.

The ice giants represent one of two fundamentally different categories of giant planets present in the Solar System, the other group being the more-familiar gas giants, which are composed of more than 90% hydrogen and helium (by mass). Their hydrogen is thought to extend all the way down to their small rocky cores, where hydrogen molecular ion transitions to metallic hydrogen under the extreme pressures of hundreds of gigapascals (GPa). [2]

The ice giants are primarily composed of heavier elements. Based on the abundance of elements in the universe, oxygen, carbon, nitrogen, and sulfur are most likely. Although the ice giants also have hydrogen envelopes, these are much smaller. They account for less than 20% of their mass. Their hydrogen also never reaches the depths necessary for the pressure to create metallic hydrogen. [2] These envelopes nevertheless limit observation of the ice giants' interiors, and thereby the information on their composition and evolution. [2]

Although Uranus and Neptune are referred to as ice giant planets, it is thought that there is a supercritical water-ammonia ocean beneath their clouds, which accounts for about two-thirds of their total mass. [12] [13]

Atmosphere and weather

The gaseous outer layers of the ice giants have several similarities to those of the gas giants. These include long-lived, high-speed equatorial winds, polar vortices, large-scale circulation patterns, and complex chemical processes driven by ultraviolet radiation from above and mixing with the lower atmosphere. [2]

Studying the ice giants' atmospheric patterns also gives insights into atmospheric physics. Their compositions promote different chemical processes and they receive far less sunlight in their distant orbits than any other planets in the Solar System (increasing the relevance of internal heating on weather patterns). [2]

The largest visible feature on Neptune is the recurring Great Dark Spot. It forms and dissipates every few years, as opposed to the similarly sized Great Red Spot of Jupiter, which has persisted for centuries. Of all known giant planets in the Solar System, Neptune emits the most internal heat per unit of absorbed sunlight, a ratio of approximately 2.6. Saturn, the next-highest emitter, only has a ratio of about 1.8. Uranus emits the least heat, one-tenth as much as Neptune. It is suspected that this may be related to its extreme 98˚ axial tilt. This causes its seasonal patterns to be very different from those of any other planet in the Solar System. [2]

There are still no complete models explaining the atmospheric features observed in the ice giants. [2] Understanding these features will help elucidate how the atmospheres of giant planets in general function. [2] Consequently, such insights could help scientists better predict the atmospheric structure and behaviour of giant exoplanets discovered to be very close to their host stars (pegasean planets) and exoplanets with masses and radii between that of the giant and terrestrial planets found in the Solar System. [2]

Interior

Because of their large sizes and low thermal conductivities, the planetary interior pressures range up to several hundred GPa and temperatures of several thousand kelvins (K). [14]

In March 2012, it was found that the compressibility of water used in ice-giant models could be off by one-third. [15] This value is important for modeling ice giants, and has a ripple effect on understanding them. [15]

Magnetic fields

The magnetic fields of Uranus and Neptune are both unusually displaced and tilted. [16] Their field strengths are intermediate between those of the gas giants and those of the terrestrial planets, being 50 and 25 times that of Earth's, respectively. The equatorial magnetic field strengths of Uranus and Neptune are respectively 75 percent and 45 percent of Earth's 0.305 gauss. [16] Their magnetic fields are believed to originate in an ionized convecting fluid-ice mantle. [16]

Spacecraft visitation

Past

Proposals

See also

Related Research Articles

<span class="mw-page-title-main">Giant planet</span> Planet much larger than the Earth

The giant planets make up a diverse type of planet much larger than Earth. They are usually primarily composed of low-boiling point materials (volatiles), rather than rock or other solid matter, but massive solid planets can also exist. There are four known giant planets in the Solar System: Jupiter, Saturn, Uranus and Neptune. Many extrasolar giant planets have been identified as orbiting other stars.

<span class="mw-page-title-main">Planet</span> Large, round non-stellar astronomical object

A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk. Planets grow in this disk by the gradual accumulation of material driven by gravity, a process called accretion. The Solar System has at least eight planets: the terrestrial planets Mercury, Venus, Earth, and Mars, and the giant planets Jupiter, Saturn, Uranus, and Neptune. These planets each rotate around an axis tilted with respect to its orbital pole. All the major planets of the Solar System other than Mercury possess a considerable atmosphere, and some share such features as ice caps, seasons, volcanism, hurricanes, tectonics, and even hydrology. Apart from Venus and Mars, the Solar System planets generate magnetic fields, and all the major planets except Venus and Mercury have natural satellites. The giant planets bear planetary rings, the most prominent being those of Saturn.

<span class="mw-page-title-main">Solar System</span> The Sun and objects orbiting it

The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. The largest of these objects are the eight planets, which in order from the Sun are four terrestrial planets ; two gas giants ; and two ice giants. The Solar System developed 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.

<span class="mw-page-title-main">Uranus</span> Seventh planet from the Sun

Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a supercritical phase of matter, which in astronomy is called 'ice' or volatiles. The planet's atmosphere has a complex layered cloud structure and has the lowest minimum temperature of 49 K out of all the Solar System's planets. It has a marked axial tilt of 82.23° with a retrograde rotation rate of 17 hours. This means that in an 84-Earth-year orbital period around the Sun, its poles get around 42 years of continuous sunlight, followed by 42 years of continuous darkness.

<span class="mw-page-title-main">Planetesimal</span> Solid objects in protoplanetary disks and debris disks

Planetesimals are solid objects thought to exist in protoplanetary disks and debris disks. Per the Chamberlin–Moulton planetesimal hypothesis, they are believed to form out of cosmic dust grains. Believed to have formed in the Solar System about 4.6 billion years ago, they aid study of its formation.

<span class="mw-page-title-main">Nebular hypothesis</span> Astronomical theory about the Solar System

The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System. It suggests the Solar System is formed from gas and dust orbiting the Sun which clumped up together to form the planets. The theory was developed by Immanuel Kant and published in his Universal Natural History and Theory of the Heavens (1755) and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded.

<span class="mw-page-title-main">Protoplanetary disk</span> Gas and dust surrounding a newly formed star

A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, because gases or other material may be falling from the inner edge of the disk onto the surface of the star. This process should not be confused with the accretion process thought to build up the planets themselves. Externally illuminated photo-evaporating protoplanetary disks are called proplyds.

<span class="mw-page-title-main">Planetary migration</span> Astronomical phenomenon

Planetary migration occurs when a planet or other body in orbit around a star interacts with a disk of gas or planetesimals, resulting in the alteration of its orbital parameters, especially its semi-major axis. Planetary migration is the most likely explanation for hot Jupiters. The generally accepted theory of planet formation from a protoplanetary disk predicts that such planets cannot form so close to their stars, as there is insufficient mass at such small radii and the temperature is too high to allow the formation of rocky or icy planetesimals.

<span class="mw-page-title-main">Formation and evolution of the Solar System</span> Modelling its structure and composition

The formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and other small Solar System bodies formed.

This page describes exoplanet orbital and physical parameters.

<span class="mw-page-title-main">History of Solar System formation and evolution hypotheses</span>

The history of scientific thought about the formation and evolution of the Solar System began with the Copernican Revolution. The first recorded use of the term "Solar System" dates from 1704. Since the seventeenth century, philosophers and scientists have been forming hypotheses concerning the origins of our Solar System and the Moon and attempting to predict how the Solar System would change in the future. René Descartes was the first to hypothesize on the beginning of the Solar System; however, more scientists joined the discussion in the eighteenth century, forming the groundwork for later hypotheses on the topic. Later, particularly in the twentieth century, a variety of hypotheses began to build up, including the now-commonly accepted nebular hypothesis.

<span class="mw-page-title-main">Nice model</span> Scenario for the dynamical evolution of the Solar System

The Nicemodel is a scenario for the dynamical evolution of the Solar System. It is named for the location of the Côte d'Azur Observatory—where it was initially developed in 2005—in Nice, France. It proposes the migration of the giant planets from an initial compact configuration into their present positions, long after the dissipation of the initial protoplanetary disk. In this way, it differs from earlier models of the Solar System's formation. This planetary migration is used in dynamical simulations of the Solar System to explain historical events including the Late Heavy Bombardment of the inner Solar System, the formation of the Oort cloud, and the existence of populations of small Solar System bodies such as the Kuiper belt, the Neptune and Jupiter trojans, and the numerous resonant trans-Neptunian objects dominated by Neptune.

The five-planet Nice model is a numerical model of the early Solar System that is a revised variation of the Nice model. It begins with five giant planets, the four that exist today plus an additional ice giant between Saturn and Uranus in a chain of mean-motion resonances.

The jumping-Jupiter scenario specifies an evolution of giant-planet migration described by the Nice model, in which an ice giant is scattered inward by Saturn and outward by Jupiter, causing their semi-major axes to jump, and thereby quickly separating their orbits. The jumping-Jupiter scenario was proposed by Ramon Brasser, Alessandro Morbidelli, Rodney Gomes, Kleomenis Tsiganis, and Harold Levison after their studies revealed that the smooth divergent migration of Jupiter and Saturn resulted in an inner Solar System significantly different from the current Solar System. During this migration secular resonances swept through the inner Solar System exciting the orbits of the terrestrial planets and the asteroids, leaving the planets' orbits too eccentric, and the asteroid belt with too many high-inclination objects. The jumps in the semi-major axes of Jupiter and Saturn described in the jumping-Jupiter scenario can allow these resonances to quickly cross the inner Solar System without altering orbits excessively, although the terrestrial planets remain sensitive to its passage.

The Nice 2 model is a model of the early evolution of the Solar System. The Nice 2 model resembles the original Nice model in that a late instability of the outer Solar System results in gravitational encounters between planets, the disruption of an outer planetesimal disk, and the migrations of the outer planets to new orbits. However, the Nice 2 model differs in its initial conditions and in the mechanism for triggering the late instability. These changes reflect the analysis of the orbital evolution of the outer Solar System during the gas disk phase and the inclusion of gravitational interactions between planetesimals in the outer disk into the model.

<span class="mw-page-title-main">Gas giant</span> Giant planet mainly composed of light elements

A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranus and Neptune are really a distinct class of giant planets, being composed mainly of heavier volatile substances. For this reason, Uranus and Neptune are now often classified in the separate category of ice giants.

<span class="mw-page-title-main">Grand tack hypothesis</span> Theory of early changes in Jupiters orbit

In planetary astronomy, the grand tack hypothesis proposes that Jupiter formed at a distance of 3.5 AU from the Sun, then migrated inward to 1.5 AU, before reversing course due to capturing Saturn in an orbital resonance, eventually halting near its current orbit at 5.2 AU. The reversal of Jupiter's planetary migration is likened to the path of a sailboat changing directions (tacking) as it travels against the wind.

<span class="mw-page-title-main">Satellite system (astronomy)</span> Set of gravitationally bound objects in orbit

A satellite system is a set of gravitationally bound objects in orbit around a planetary mass object or minor planet, or its barycenter. Generally speaking, it is a set of natural satellites (moons), although such systems may also consist of bodies such as circumplanetary disks, ring systems, moonlets, minor-planet moons and artificial satellites any of which may themselves have satellite systems of their own. Some bodies also possess quasi-satellites that have orbits gravitationally influenced by their primary, but are generally not considered to be part of a satellite system. Satellite systems can have complex interactions including magnetic, tidal, atmospheric and orbital interactions such as orbital resonances and libration. Individually major satellite objects are designated in Roman numerals. Satellite systems are referred to either by the possessive adjectives of their primary, or less commonly by the name of their primary. Where only one satellite is known, or it is a binary with a common centre of gravity, it may be referred to using the hyphenated names of the primary and major satellite.

<span class="mw-page-title-main">Pebble accretion</span>

Pebble accretion is the accumulation of particles, ranging from centimeters up to meters in diameter, into planetesimals in a protoplanetary disk that is enhanced by aerodynamic drag from the gas present in the disk. This drag reduces the relative velocity of pebbles as they pass by larger bodies, preventing some from escaping the body's gravity. These pebbles are then accreted by the body after spiraling or settling toward its surface. This process increases the cross section over which the large bodies can accrete material, accelerating their growth. The rapid growth of the planetesimals via pebble accretion allows for the formation of giant planet cores in the outer Solar System before the dispersal of the gas disk. A reduction in the size of pebbles as they lose water ice after crossing the ice line and a declining density of gas with distance from the sun slow the rates of pebble accretion in the inner Solar System resulting in smaller terrestrial planets, a small mass of Mars and a low mass asteroid belt.

The following outline is provided as an overview of and topical guide to Uranus:

References

  1. ↑ D'Angelo, G.; Weidenschilling, S. J.; Lissauer, J. J.; Bodenheimer, P. (2021). "Growth of Jupiter: Formation in disks of gas and solids and evolution to the present epoch". Icarus. 355: 114087. arXiv: 2009.05575 . Bibcode:2021Icar..35514087D. doi:10.1016/j.icarus.2020.114087. S2CID   221654962.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 Hofstadter, Mark (2011), "The Atmospheres of the Ice Giants, Uranus and Neptune" (PDF), White Paper for the Planetary Science Decadal Survey , US National Research Council, pp. 1–2, retrieved 18 January 2015
  3. ↑ Science Fiction Citations, Citations for gas giant n.
  4. 1 2 Mark Marley, "Not a Heart of Ice", The Planetary Society, 2 April 2019. read
  5. ↑ Bova, B. 1971, The Many Worlds of Science Fiction (Boston, MA: E.P. Dutton)
  6. ↑ James A. Dunne and Eric Burgess, The Voyage of Mariner 10: Mission to Venus and Mercury, Scientific and Technical Information Division, National Aeronautics and Space Administration, 1978, 224 pages, page 2. read
  7. ↑ Molaverdikhani, Karan (2019). "From Cold to Hot Irradiated Gaseous Exoplanets: Toward an Observation-based Classification Scheme". The Astrophysical Journal. 873 (1): 32. arXiv: 1809.09629 . Bibcode:2019ApJ...873...32M. doi: 10.3847/1538-4357/aafda8 . S2CID   119357572.
  8. ↑ Lissauer, J. J.; Hubickyj, O.; D'Angelo, G.; Bodenheimer, P. (2009). "Models of Jupiter's growth incorporating thermal and hydrodynamic constraints". Icarus. 199 (2): 338–350. arXiv: 0810.5186 . Bibcode:2009Icar..199..338L. doi:10.1016/j.icarus.2008.10.004. S2CID   18964068.
  9. 1 2 D'Angelo, Gennaro; Durisen, Richard H.; Lissauer, Jack J. (December 2010). "Giant Planet Formation". In Seager, Sara (ed.). Exoplanets. University of Arizona Press. pp. 319–346. arXiv: 1006.5486 . Bibcode:2010exop.book..319D. ISBN   978-0-8165-2945-2.
  10. ↑ Levison, Harold F.; Kretke, Katherine A.; Duncan, Martin J. (2015). "Growing the gas-giant planets by the gradual accumulation of pebbles". Nature. 524 (7565): 322–324. arXiv: 1510.02094 . Bibcode:2015Natur.524..322L. doi:10.1038/nature14675. PMID   26289203. S2CID   4458098.
  11. 1 2 3 4 5 6 7 8 Boss, Alan P. (December 2003). "Rapid Formation of Outer Giant Planets by Disk Instability". The Astrophysical Journal. 599 (1): 577–581. Bibcode:2003ApJ...599..577B. doi: 10.1086/379163 ., §1–2
  12. ↑ NASA Completes Study of Future ‘Ice Giant’ Mission Concepts. NASA TV. 20 June 2017.
  13. ↑ [https://www.lpi.usra.edu/icegiants/mission_study/IceGiants_EGUPresentation_2017_04_24.pdf On to the Ice Giants]. (PDF) Pre-Decadal study summary. NASA. Presented at the European Geophysical Union, 24 April 2017.
  14. ↑ Nellis, William (February 2012). "Viewpoint: Seeing Deep Inside Icy Giant Planets". Physics . 5 (25): 25. Bibcode:2012PhyOJ...5...25N. doi: 10.1103/Physics.5.25 .
  15. 1 2 "The Interiors of Ice Giant Planets". Archived from the original on 2012-05-03.{{cite web}}: CS1 maint: unfit URL (link)
  16. 1 2 3 "The Nature and Origin of Magnetic Fields".
  17. ↑ Christophe, Bruno; Spilker, L. J.; Anderson, J. D.; André, N.; Asmar, S. W.; Aurnou, J.; Banfield, D.; Barucci, A.; Bertolami, O.; Bingham, R.; Brown, P; Cecconi, B.; Courty, J.-M.; Dittus, H.; Fletcher, L. N.; Foulon, B.; Francisco, F.; Gil, P. J. S.; Glassmeier, K. H.; Grundy, W.; Hansen, C.; Helbert, J.; Helled, R.; Hussmann, H.; Lamine, B.; Lämmerzahl, C.; Lamy, L.; Lehoucq, R.; Lenoir, B.; Levy, A.; Orton, G.; Páramos, J.; Poncy, J.; Postberg, F.; Progrebenko, S. V.; Reh, K. R.; Reynaud, S.; Robert, C.; Samain, E.; Saur, J; Sayanagi, K. M.; Schmitz, N.; Selig, H.; Sohl, F.; Spilker, T. R.; Srama, R.; Stephan, K.; Touboul, P.; Wolf, P. (8 July 2012). "OSS (Outer Solar System): a fundamental and planetary physics mission to Neptune, Triton and the Kuiper Belt" (PDF). Experimental Astronomy. Springer. 34 (2): 203–242. arXiv: 1106.0132 . Bibcode:2012ExA....34..203C. doi:10.1007/s10686-012-9309-y. S2CID   55295857. Archived from the original (PDF) on 26 May 2019. Retrieved 26 May 2019– via UCLA Simulated Planetary Interiors Lab.
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