View source for Astronomy:Rhea (moon)

{{Short description|Moon of Saturn}}
{{Infobox planet
| name               = Rhea
| mpc_name           = Saturn V
| pronounced         = {{IPAc-en|ˈ|r|iː|.|ə}}<ref>{{cite journal |last1=Consulmagno |first1=G. |last2=Ryche |first2=H. |date=Feb 9, 1982 |title=Pronouncing the names of the moons of Saturn |url=https://www.vaticanobservatory.org/wp-content/uploads/2019/12/Consolmagno-Reiche-Pronouncing-Moons-of-Saturn.pdf |journal=EOS |volume=63 |issue=6 |pages=146–147 |doi=10.1029/EO063i006p00146 |access-date=Nov 30, 2022}}</ref>
| named_after        = [[Biology:Rhea (mythology)|Ῥέᾱ]] ''Rheā''
| adjectives         = Rhean {{IPAc-en|ˈ|r|iː|.|ən}}<ref>Moore et al. (1984) "The Geomorphology of Rhea", ''Proceedings of the fifteenth Lunar and Planetary Science'', Part 2, p C-791–C-794</ref>
| image              = PIA07763 Rhea full globe5.jpg
| caption            = ''[[Astronomy:Cassini–Huygens|Cassini]]'' mosaic of Rhea
| discoverer         = G. D. Cassini<ref name=space.com.Rhea/>
| discovered         = December 23, 1672<ref name=space.com.Rhea>{{cite web |url=http://www.space.com/20577-rhea-saturn-s-dirty-snowball-moon.html |title=Rhea: Saturn's dirty snowball moon |last=Tillman |first=Nola Taylor |date=2016-06-29 |website=space.com}}</ref>
| orbit_ref          = <ref name="NSES" />
| semimajor          = {{val|527108|u=km}}
| eccentricity       = {{val|0.0012583}}
| period             = {{val|4.518212|u=[[Day|d]]}}
| avg_speed          = 8.48 km/s{{efn|name=calculated|Calculated on the basis of other parameters.}}
| inclination        = 0.345° (to Saturn's equator)
| satellite_of       = [[Astronomy:Saturn|Saturn]]
| mean_radius        = {{val|763.5|0.5|u=km}}<ref name="Jacobson2022">{{cite journal |last1=Jacobson |first1=Robert. A. |title=The Orbits of the Main Saturnian Satellites, the Saturnian System Gravity Field, and the Orientation of Saturn's Pole* |journal=The Astronomical Journal |date=1 November 2022 |volume=164 |issue=5 |pages=199 |doi=10.3847/1538-3881/ac90c9|bibcode=2022AJ....164..199J |s2cid=252992162 |doi-access=free }}</ref>
| dimensions         = 1532.4&thinsp;×&thinsp;1525.6&thinsp;×&thinsp;1524.4 km <ref name="Roatsch et al. 2009" />
| surface_area       = {{val|7337000|u=km<sup>2</sup>}}
| mass               = {{val|2.3064854|0.0000522|e=21|u=kg}}<ref name="Jacobson2022"/> (~3.9{{e|-4}} Earths)
| density            = {{val|1.2372|0.0029|u=g/cm<sup>3</sup>}}<ref name="Jacobson2022"/>
| surface_grav       = {{Gr|2.306|763.8|3}} [[Physics:Acceleration|m/s<sup>2</sup>]]
| moment_of_inertia_factor = {{val|0.3911|0.0045}}<ref name="Anderson2007">{{cite journal |last1= Anderson|first1=J. D.|last2= Schubert|first2= G.|title= Saturn's satellite Rhea is a homogeneous mix of rock and ice|journal= Geophysical Research Letters |volume= 34|issue= 2|pages=L02202|year= 2007|doi= 10.1029/2006GL028100|bibcode= 2007GeoRL..34.2202A|doi-access= free}}</ref> (disputed/unclear<ref name="Anderson2008" />)
| escape_velocity    = {{V2|2.306|763.8|3}} km/s
| rotation           = {{val|4.518212|u=d}} <br /> (synchronous)
| axial_tilt         = zero
| albedo             = {{val|0.949|0.003}} ([[Physics:Geometric albedo|geometric]]) <ref name="Verbiscer et al. 2007" />
| magnitude          = 10 <ref name="Observatorio ARVAL" />
| temp_name1         = [[Kelvin]]
| min_temp_1         = 53 [[Kelvin|K]]
| mean_temp_1        = &nbsp;
| max_temp_1         = 99 K
}}

'''Rhea''' ({{IPAc-en|ˈ|r|iː|.|ə}}) is the second-largest [[Astronomy:Natural satellite|moon]] of [[Astronomy:Saturn|Saturn]] and the ninth-largest moon in the [[Astronomy:Solar System|Solar System]], with a surface area that is comparable to the area of {{wipe|Australia}}. It is the smallest body in the [[Astronomy:Solar System|Solar System]] for which precise measurements have confirmed a shape consistent with [[Astronomy:Hydrostatic equilibrium|hydrostatic equilibrium]].<ref>{{Cite journal |last=Thomas |first=P.C. |date=2010 |title=Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission |url=http://www.ciclops.org/media/sp/2011/6794_16344_0.pdf |journal=Icarus |archive-url=https://web.archive.org/web/20181223003125/http://www.ciclops.org/media/sp/2011/6794_16344_0.pdf |archive-date=2018-12-23}}</ref>  It was discovered in 1672 by Giovanni Domenico Cassini.

== Discovery ==
[[File:Giovanni Cassini.jpg|thumb|left|upright=0.6|Giovanni Domenico Cassini, discoverer of Rhea in 1672]]
Rhea was discovered by Giovanni Domenico Cassini on 23 December 1672.<ref name=space.com.Rhea/>  It was the second [[Astronomy:Moons of Saturn|moon of Saturn]] that Cassini discovered, and the third moon discovered around Saturn overall.<ref name=space.com.Rhea/>

==Name==
Rhea is named after the Titan [[Biology:Rhea (mythology)|Rhea]] of [[Religion:Greek mythology|Greek mythology]], the "mother of the gods" and wife of [[Religion:Cronus|Kronos]], the [[Religion:Interpretatio graeca|Greek counterpart]] of the god [[Religion:Saturn (mythology)|Saturn]]. It is also designated '''Saturn&nbsp;V''' (being the fifth major moon going outward from the planet, after Mimas, Enceladus, Tethys, and Dione).<ref>{{Cite web|url=https://solarsystem.nasa.gov/moons/saturn-moons/rhea/in-depth/|title=In Depth {{!}} Rhea|date=December 19, 2019|website=NASA Solar System Exploration|publisher=NASA Science|access-date=January 7, 2020}}</ref><ref name=":0">{{Cite web|url=https://planetarynames.wr.usgs.gov/Page/Planets|title=Planet and Satellite Names and Discoverers|date=July 21, 2006|work=Gazetteer of Planetary Nomenclature|publisher=USGS Astrogeology|access-date=January 7, 2020}}</ref>

Cassini named the four moons he discovered (Tethys, Dione, Rhea, and Iapetus) ''[[Astronomy:Sidera Lodoicea|Sidera Lodoicea]]'' (the stars of Louis) to honor King Louis XIV.<ref name=space.com.Rhea/>  Astronomers fell into the habit of referring to them and [[Astronomy:Titan (moon)|Titan]] as ''Saturn&nbsp;I'' through ''Saturn&nbsp;V''.<ref name=space.com.Rhea/>  Once Mimas and Enceladus were discovered, in 1789, the numbering scheme was extended to ''Saturn&nbsp;VII'', and then to ''Saturn&nbsp;VIII'' with the discovery of [[Astronomy:Hyperion (moon)|Hyperion]] in 1848.<ref name=":0" />

Rhea was not named until 1847, when [[Biography:John Herschel|John Herschel]] (son of William Herschel, discoverer of the planet [[Astronomy:Uranus|Uranus]], and two other moons of Saturn, Mimas and [[Astronomy:Enceladus|Enceladus]]) suggested in ''Results of Astronomical Observations made at the Cape of Good Hope'' that the names of the Titans, sisters and brothers of Kronos (Saturn, in Roman mythology), be used.<ref name="Lassell1848" /><ref name=space.com.Rhea/>

== Physical characteristics ==

=== Size, mass, and internal structure ===
[[File:Rhea, Earth & Moon size comparison.jpg|left|thumb|250x250px|Size comparison of [[Astronomy:Earth|Earth]] (right), the Moon (left top), and Rhea (left down)]]
Rhea is an icy body with a density of about 1.236 g/cm<sup>3</sup>. This low [[Physics:Density|density]] indicates that it is made of ~25% rock (density ~3.25 g/cm<sup>3</sup>) and ~75% water ice (density ~0.93 g/cm<sup>3</sup>). Although Rhea is the ninth-largest moon, it is only the tenth-most massive moon. Indeed, [[Astronomy:Oberon (moon)|Oberon]], the second-largest moon of Uranus, has almost the same size, but is significantly denser than Rhea (1.63 vs 1.24) and thus more massive, although Rhea is slightly larger by volume.
<ref group="lower-alpha">The moons more massive than Rhea are: the [[Astronomy:Moon|Moon]], the four [[Astronomy:Galilean moons|Galilean moons]], Titan, Triton, Titania, and Oberon. Oberon, Uranus's second-largest moon, has a radius that is ~0.4% smaller than Rhea's, but a density that is ~26% greater. See [http://ssd.jpl.nasa.gov/?sat_phys_par JPLSSD.]</ref>

Before the [[Astronomy:Cassini–Huygens|''Cassini-Huygens'']] mission, it was assumed that Rhea had a rocky core.<ref name="Anderson2003" />  However, measurements taken during a close flyby by the [[Astronomy:Cassini–Huygens|''Cassini'']] orbiter in 2005 cast this into doubt. In a paper published in 2007 it was claimed that the axial dimensionless [[Physics:Moment of inertia|moment of inertia]] coefficient was 0.4.{{refn | group = lower-alpha | More precisely, 0.3911.<ref name="Anderson_2007" /> }}<ref name="Anderson_2007" />  Such a value indicated that Rhea had an almost homogeneous interior (with some compression of ice in the center) while the existence of a rocky core would imply a moment of inertia of about 0.34.<ref name="Anderson2003" />  In the same year another paper claimed the moment of inertia was about 0.37.{{refn | group = lower-alpha | More precisely, 0.3721.<ref name="Iess2007" /> }} Rhea being either partially or fully differentiated would be consistent with the observations of the ''Cassini'' probe.<ref name="Iess2007" /> A year later yet another paper claimed that the moon may not be in hydrostatic equilibrium meaning that the moment of inertia cannot be determined from the gravity data alone.<ref name="MacKenzie2008" />  In 2008 an author of the first paper tried to reconcile these three disparate results. He concluded that there is a systematic error in the ''Cassini'' radio Doppler data used in the analysis, but after restricting the analysis to a subset of data obtained closest to the moon, he arrived at his old result that Rhea was in hydrostatic equilibrium and had a moment of inertia of about 0.4, again implying a homogeneous interior.<ref name="Anderson2008" />

The triaxial shape of Rhea is consistent with a homogeneous body in [[Astronomy:Hydrostatic equilibrium|hydrostatic equilibrium]] rotating at Rhea's angular velocity.<ref name="Thomas2007" /> Modelling in 2006 suggested that Rhea could be barely capable of sustaining an internal liquid-water ocean through heating by [[Physics:Radioactive decay|radioactive decay]]; such an ocean would have to be at about 176&nbsp;K, the eutectic temperature for the water–ammonia system.<ref>
{{cite journal| doi = 10.1016/j.icarus.2006.06.005| last1 = Hussmann| first1 = Hauke| last2 = Sohl| first2 = Frank| last3 = Spohn| first3 = Tilman| date = November 2006| title = Subsurface oceans and deep interiors of medium-sized outer planet satellites and large trans-neptunian objects| journal = Icarus| volume = 185| issue = 1| pages = 258–273| url = https://www.researchgate.net/publication/225019299| bibcode = 2006Icar..185..258H| ref = {{sfnRef|Hussmann Sohl et al.|2006}}}}</ref> More recent indications are that Rhea has a homogeneous interior and hence that this ocean does not exist.<ref name=Anderson2008/>

<div class="center">
{{Annotated image 
|image        = Color map of Rhea PIA18438 Nov. 2014.jpg
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| float       = center 
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| caption = {{center|Enhanced-color map (28 MB), leading hemisphere on right}}}}
{{Annotated image 
| image       = Color Rhea polar maps PIA18438 Nov. 2014.jpg
| image-width = 600
| height      = 275 <!-- to crop the lower part of the image -->
| float       = center 
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| caption     = {{center|Enhanced-color maps<br />north and south hemispheres}}
}}
{{Annotated image 
| image       = PIA18438-SaturnMoon-Rhea-20141104-fig2.jpg
| image-width = 600
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| caption     = {{center|Enhanced-color maps<br />trailing and leading hemispheres}}
}}
</div>

=== Surface features ===
{{main|Astronomy:List of geological features on Rhea}}
Rhea's features resemble those of Dione, with dissimilar leading and trailing hemispheres, suggesting similar composition and histories. The temperature on Rhea is 99&nbsp;K (−174&nbsp;°C) in direct sunlight and between 73&nbsp;K (−200&nbsp;°C) and 53&nbsp;K (−220&nbsp;°C) in the shade.
[[File:PIA18310-SaturnMoon-Rhea-20150210.jpg|thumb|left|250px|Surface features on Rhea well defined due to the lighting.]]
Rhea has a rather typical heavily [[Astronomy:Impact crater|cratered]] surface,<ref name="MooreSchenk_2004" /> with the exceptions of a few large Dione-type chasmata or fractures (wispy terrain) on the trailing hemisphere (the side facing away from the direction of motion along Rhea's orbit)<ref name="Wagner2008" /> and a very faint "line" of material at Rhea's equator that may have been deposited by material deorbiting from its rings.<ref name="Schenk2009" />  Rhea has two very large impact basins on its anti-Cronian hemisphere (facing away from Saturn), which are about 400 and 500&nbsp;km across.<ref name="Wagner2008" />  The more northerly and less degraded of the two, called Tirawa, is roughly comparable to the basin Odysseus on Tethys.<ref name="MooreSchenk_2004" />  There is a 48&nbsp;km-diameter impact crater at 112°W that is prominent because of an extended system of bright [[Astronomy:Ray system|ray]]s.<ref name="Wagner2008" />  This crater, called Inktomi, is nicknamed "The Splat", and may be one of the youngest craters on the inner moons of Saturn.<ref name="Wagner2008" /> No evidence of any endogenic activity has been discovered.<ref name="Wagner2008" />
[[File:Rhea at approximately 2,348 miles (3,778 kilometers) away.jpg|thumb|right|200px|Closeup showing two craters on Rhea's surface taken in 2013 by [[Astronomy:Cassini–Huygens|''Cassini'' spacecraft.]]]]
Its surface can be divided into two geologically different areas based on [[Astronomy:Impact crater|crater]] density; the first area contains craters which are larger than 40&nbsp;km in diameter, whereas the second area, in parts of the polar and equatorial regions, has only craters under that size. This suggests that a major resurfacing event occurred some time during its formation. The leading hemisphere is heavily cratered and uniformly bright. As on [[Astronomy:Callisto (moon)|Callisto]], the craters lack the high relief features seen on the [[Astronomy:Moon|Moon]] and [[Astronomy:Mercury (planet)|Mercury]]. It has been theorized that these cratered plains are up to four billion years old on average.<ref>{{Cite web|url=https://solarsystem.nasa.gov/planets/rhea|archive-url=https://web.archive.org/web/20160214000303/http://solarsystem.nasa.gov/planets/rhea|url-status=dead|archive-date=2016-02-14|title=Rhea - Overview {{!}} Planets - NASA Solar System Exploration|website=NASA Solar System Exploration|access-date=2017-09-21}}</ref>  On the trailing hemisphere there is a network of bright swaths on a dark background and few visible craters. It had been thought that these bright areas might be material ejected from ice [[Earth:Volcano|volcano]]es early in Rhea's history when its interior was still liquid. However, observations of Dione, which has an even darker trailing hemisphere and similar but more prominent bright streaks, show that the streaks are actually ice cliffs resulting from extensive fracturing of the moon's surface.{{Citation needed|date=February 2013}} The extensive dark areas are thought to be deposited [[Astronomy:Tholin|tholin]]s, which are a mix of complex [[Chemistry:Organic compound|organic compound]]s generated on the ice by [[Chemistry:Pyrolysis|pyrolysis]] and [[Physics:Radiolysis|radiolysis]] of simple compounds containing carbon, nitrogen and hydrogen.<ref name='Cruikshank 2005'>[http://astrochemistry.org/docs/Cruikshanketal2005.pdf A spectroscopic study of the surfaces of Saturn's large satellites: H2O ice, tholins, and minor constituents] (PDF). Dale P. Cruikshank, Tobias. Owen, Cristina Dalle Ore, Thomas R. Geballe, Ted L. Roush, Catherine de Bergh, Scott A. Sandford, Francois Poulet, Gretchen K. Benedix, Joshua P. Emery. ''Icarus'', 175, pages: 268–283, 2 March 2005.</ref>

The January 17, 2006 distant flyby by the ''Cassini'' spacecraft yielded images of the wispy hemisphere at better resolution and a lower Sun angle than previous observations. Images from this and subsequent flybys showed that Rhea's streaks in fact are tectonically formed ice cliffs (''chasmata'') similar to those of Dione.

==Formation==
The moons of 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 giant planets formed, they were surrounded by discs of material that gradually coalesced into moons. However, a proposed model for the formation of [[Astronomy:Titan (moon)|Titan]] may also shine a new light on the origin of Rhea and Iapetus. In this model, Titan was formed in a series of giant impacts between pre-existing moons, and Rhea and Iapetus are thought to have formed from part of the debris of these collisions.<ref>{{cite web |title=Giant impact scenario may explain the unusual moons of Saturn |work=Space Daily |date=2012 |url=http://www.spacedaily.com/reports/Giant_impact_scenario_may_explain_the_unusual_moons_of_Saturn_999.html |access-date=2012-10-19 }}</ref>

== Atmosphere ==
On November 27, 2010, [[Organization:NASA|NASA]] announced the discovery of a tenuous atmosphere—an [[Earth:Exosphere|exosphere]]. It consists of oxygen and carbon dioxide in proportion of roughly 5 to 2. The surface density of the exosphere is from 10<sup>5</sup> to 10<sup>6</sup> molecules in a cubic centimeter depending on local temperature. The main source of oxygen is [[Physics:Radiolysis|radiolysis]] of water ice at the surface by ions supplied by the [[Astronomy:Magnetosphere of Saturn|magnetosphere of Saturn]]. The source of the carbon dioxide is less clear, but it may be related to oxidation of the organics present in ice or to [[Physics:Outgassing|outgassing]] of the moon's interior.<ref name="atmosphere" /><ref name="Teolis2010" />

== Possible ring system ==
{{main|Astronomy:Rings of Rhea}}
On March 6, 2008, [[Organization:NASA|NASA]] announced that Rhea may have a tenuous ring system. This would mark the first discovery of rings around a moon.  The rings' existence was inferred by observed changes in the flow of electrons trapped by Saturn's magnetic field as ''Cassini'' passed by Rhea.<ref name="rings" /><ref name="Jones2008" /><ref name="LakdawallaE" />  Dust and debris could extend out to Rhea's [[Astronomy:Hill sphere|Hill sphere]], but were thought to be denser nearer the moon, with three narrow rings of higher density. The case for a ring was strengthened by the subsequent finding of the presence of a set of small ultraviolet-bright spots distributed along Rhea's equator (interpreted as the impact points of deorbiting ring material).<ref name="Lakdawalla2" />  However, when ''Cassini'' made targeted observations of the putative ring plane from several angles, no evidence of ring material was found, suggesting that another explanation for the earlier observations is needed.<ref name="Tiscareno2010" /><ref name="norings" />

== Exploration ==
The first images of Rhea were obtained by ''[[Astronomy:Voyager program|Voyager 1 & 2]]'' spacecraft in 1980–1981.

There were five close targeted fly-bys by the ''[[Astronomy:Cassini–Huygens|Cassini]]'' orbiter: at a distance of 500&nbsp;km on November 26, 2005, at a distance of 5,750&nbsp;km on August 30, 2007, at a distance of 100&nbsp;km on March 2, 2010, and at 69&nbsp;km flyby on January 11, 2011<ref name="CookJ2011" /> and a last flyby at 992&nbsp;km on March 9, 2013.<ref name="LastFlybyRhea" />  Rhea has been also imaged many times from long to moderate distances by the orbiter.

== Gallery ==
<gallery class="center" widths="100px" heights="100px">
File:Rhean rings PIA10246 Full res.jpg|An artist's impression of Rhea's rings
File:Rhea true color.jpg|''[[Astronomy:Cassini–Huygens|Cassini]]'' color image of Rhea - large crater Powehiwehi (right center) - [[Astronomy:Chasma|chasma]]ta stretch vertically above (past crater Wakonda, near the [[Astronomy:Terminator (solar)|terminator]]) - Onokoro Catenae (lower left).
File:Rhea ice cliffs.jpg|Image of the wispy hemisphere, showing ice cliffs - Powehiwehi (upper center); chasmata stretch from upper left to right center - Onokoro Catenae (lower right).
File:PIA08148 (Rhea-Splat).jpg|View of Rhea's leading hemisphere with crater Inktomi and its prominent [[Astronomy:Ray system|ray system]] just below center; impact basin Tirawa is at upper left
File:PIA19057-SaturnMoon-Rhea-20150209.jpg|Enhanced-color views of Rhea taken by ''Cassini'' on 9 February 2015
File:PIA18316-SaturnMoon-Rhea-Cassini-20150210.jpg|Rhea's horizon viewed on 10 February 2015.
</gallery>

== See also ==
* [[Astronomy:Planet#Objects formerly considered planets|Former classification of planets]]
* [[Astronomy:List of natural satellites|List of natural satellites]]
* Rhea in fiction
* [[Astronomy:Rings of Rhea|Rings of Rhea]]
* [[Astronomy:Subsatellite|Subsatellite]]
* [[Astronomy:Moons of Saturn|Moons of Saturn]]

== Notes ==
{{Reflist
| colwidth = 30em
| group = lower-alpha
}}

== References ==
{{Reflist
| colwidth = 30em
| refs =

<ref name="NSES">
[http://www.minorplanetcenter.org/iau/NatSats/NaturalSatellites.html Natural Satellites Ephemeris Service] ''Minor Planet Center''
</ref>

<ref name="Roatsch et al. 2009">
{{cite book| doi = 10.1007/978-1-4020-9217-6_24| last1 = Roatsch| first1 = T.| last2 = Jaumann| first2 = R.| last3 = Stephan| first3 = K.| last4 = Thomas| first4 = P. C.| year = 2009| chapter = Cartographic Mapping of the Icy Satellites Using ISS and VIMS Data| title = Saturn from Cassini-Huygens| pages = 763–781| isbn = 978-1-4020-9216-9| ref = {{sfnRef|Roatsch Jaumann et al.|2009}}}}
</ref>

<ref name="Verbiscer et al. 2007">
{{cite journal| doi = 10.1126/science.1134681| last1 = Verbiscer| first1 = A.| last2 = French| first2 = R.| last3 = Showalter| first3 = M.| last4 = Helfenstein| first4 = P.| title = Enceladus: Cosmic Graffiti Artist Caught in the Act| journal = Science| volume = 315| issue = 5813| page = 815| date = 9 February 2007| pmid = 17289992| bibcode = 2007Sci...315..815V| s2cid = 21932253| ref = {{sfnRef|Verbiscer French et al.|2007}}}} (supporting online material, table S1)
</ref>

<ref name="Observatorio ARVAL">
{{cite web
| author = Observatorio ARVAL
| title = Classic Satellites of the Solar System
| publisher = Observatorio ARVAL
| date = April 15, 2007
| url = http://www.oarval.org/ClasSaten.htm
| access-date = 2011-12-17
| ref = {{sfnRef|Observatorio ARVAL}}
}}
</ref>

<ref name="Lassell1848">
As reported by William Lassell, [http://adsabs.harvard.edu//full/seri/MNRAS/0008//0000042.000.html Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 3, pp. 42–43] (January 14, 1848)
</ref>

<ref name="Anderson2003">
{{cite journal
| doi = 10.1016/S0031-9201(03)00035-9
| last1 = Anderson
| first1 = J. D.
| last2 = Rappaport
| first2 = N. J.
| last3 = Giampieri
| first3 = G.
| display-authors = 3
| last4 = Schubert
| first4 = Gerald
| last5 = Moore
| first5 = William B.
| date = 2003
| title = Gravity field and interior structure of Rhea
| journal = [[Earth:Physics of the Earth and Planetary Interiors|Physics of the Earth and Planetary Interiors]]
| volume = 136
| issue = 3–4
| pages = 201–213
| bibcode = 2003PEPI..136..201A
| citeseerx = 10.1.1.7.5250
}}
</ref>

<ref name="Anderson_2007">
{{cite journal
| doi = 10.1029/2006GL028100
| last1 = Anderson
| first1 = J. D.
| last2 = Schubert
| first2 = J.
| date = 2007
| title = Saturn's satellite Rhea is a homogeneous mix of rock and ice
| journal = [[Earth:Geophysical Research Letters|Geophysical Research Letters]]
| volume = 34
| issue = 2
| pages = L02202
|bibcode = 2007GeoRL..3402202A | doi-access = free
}}
</ref>

<ref name="Iess2007">
{{Cite journal |doi=10.1016/j.icarus.2007.03.027 |last1=Iess |first1=L. |last2=Rappaport |first2=N. |last3=Tortora |first3=P. |last4=Lunine |first4=Jonathan I. |last5=Armstrong |first5=J. |last6=Asmar |first6=S. |last7=Somenzi |first7=L. |last8=Zingoni |first8=F. |title=Gravity field and interior of Rhea from Cassini data analysis |journal=Icarus |volume=190 |issue=2 |pages=585 |year=2007 |bibcode=2007Icar..190..585I }}
</ref>

<ref name="MacKenzie2008">
{{Cite journal | doi = 10.1029/2007GL032898 | last1 = MacKenzie | first1 = R. A. | last2 = Iess | first2 = L. | last3 = Tortora | first3 = P. | last4 = Rappaport | first4 = N. J. | title = A non-hydrostatic Rhea | journal = Geophysical Research Letters | volume = 35 | issue = 5 | pages = L05204 | year = 2008 | bibcode=2008GeoRL..3505204M| doi-access = free | hdl = 11573/17051 | hdl-access = free }}
</ref>

<ref name="Anderson2008">
{{cite conference
| last = Anderson
| first = John D.
|date=July 2008
| title = Rhea's Gravitational Field and Internal Structure
| conference = 37th COSPAR Scientific Assembly. Held 13–20 July 2008, in Montréal, Canada
| page = 89
| bibcode = 2008cosp...37...89A
}}
</ref>

<ref name="Thomas2007">
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== External links ==
* [https://web.archive.org/web/20070801204714/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sat_Rhea Rhea Profile] at [http://solarsystem.nasa.gov NASA's Solar System Exploration site]
* [https://web.archive.org/web/20060831203603/http://www.planetary.org/explore/topics/saturn/rhea.html The Planetary Society: Rhea]
* [http://ciclops.org/search.php?x=20&y=7&search=Rhea ''Cassini'' images of Rhea] {{Webarchive|url=https://web.archive.org/web/20110813151222/http://ciclops.org/search.php?x=20&y=7&search=Rhea |date=2011-08-13 }}
* [http://photojournal.jpl.nasa.gov/target/Rhea Images of Rhea at JPL's Planetary Photojournal]
* Movie of [https://web.archive.org/web/20100601171509/http://sos.noaa.gov/videos/Rhea.mov Rhea's rotation] from the National Oceanic and Atmospheric Administration site
* Rhea [http://www.ciclops.org/view/7313/Map_of_Rhea_-_March_2012 global] and [http://www.ciclops.org/view/7314/Rhea_Polar_Maps_-_March_2012 polar] basemaps (March 2012) from Cassini images
* [http://www.ciclops.org/view/6626/The_Rhea_Atlas Rhea altlas] {{Webarchive|url=https://web.archive.org/web/20130424012008/http://www.ciclops.org/view/6626/The_Rhea_Atlas |date=2013-04-24 }} (released December 2010) from Cassini images
* [http://planetarynames.wr.usgs.gov/Page/RHEA/target Rhea nomenclature] and [http://planetarynames.wr.usgs.gov/images/rhea_comp.pdf Rhea map with feature names] from the [http://planetarynames.wr.usgs.gov USGS planetary nomenclature page]
* [https://www.google.com/maps/space/rhea/@3.4035608,-102.4187081,6475987m/data=!3m1!1e3 Google Rhea 3D], interactive map of the moon
* [https://www.bbc.co.uk/news/science-environment-11834954 Saturn's moon Rhea has thin atmosphere]

{{Moons of Saturn}}
{{Solar System moons (compact)}}
{{Saturn}}
{{Atmospheres}}

[[Category:Moons of Saturn]]

{{Sourceattribution|Rhea (moon)}}