{{Short description|Dwarf planet in the asteroid belt}}
{{redirect|1 Ceres|the rocket|Ceres-1}}
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{{Use dmy dates|date=August 2024}}
{{Use British English|date=August 2024}}
{{Infobox planet
| minorplanet = yes
| type = dwarf planet
| name = Ceres
| symbol = [[File:Ceres symbol (bold).svg|24px|⚳|class=skin-invert]]
| image = Ceres - RC3 - Haulani Crater (22381131691) (cropped).jpg
| caption = Ceres as imaged by [[Dawn (spacecraft)|''Dawn'']], May 2015. The two bright spots are the crater [[Haulani (crater)|Haulani]] (right), and the floor of the crater [[Oxo (crater)|Oxo]] (left).
| discovery_ref = <ref>{{Cite book |last=Schmadel |first=Lutz |url=https://books.google.com/books?id=KWrB1jPCa8AC&pg=PA15 |title=Dictionary of minor planet names |publisher=Springer |year=2003 |isbn=978-3-540-00238-3 |edition=5th |location=Germany |page=15 |author-link=Lutz D. Schmadel |access-date=21 January 2021 |archive-url=https://web.archive.org/web/20210216235253/https://books.google.com/books?id=KWrB1jPCa8AC&pg=PA15 |archive-date=16 February 2021 |url-status=live}}</ref>
| discoverer = [[Giuseppe Piazzi]]
| discovered = 1 January 1801
| mpc_name = (1) Ceres
| pronounced = {{IPAc-en|ˈ|s|ɪər|iː|z}}, {{respell|SEER|eez}}
| named_after = [[Ceres (mythology)|Cerēs]]
| alt_names = (1) Ceres<!--{{Hlist
 | A801 AA
 | A899 OF
 | 1943 XB
 }}-->
| adjectives = Cererian, -ean ({{IPAc-en|s|ᵻ|ˈ|r|ɪər|i|ə|n}})
| mp_category = {{Ubl
 |[[dwarf planet]]
 |[[asteroid]]
 }}
| orbit_ref = <ref name="jpl_sbdb" />
| epoch = 21 January 2022 ([[Julian day|JD]] 2459600.5)
| aphelion = {{Convert|{{sigfig|2.98318|3}}|AU|e6km|abbr=unit|lk=on}}
| perihelion = {{Convert|{{sigfig|2.54891|3}}|AU|e6km|abbr=unit}}
| time_periastron = 7 December 2022
| semimajor = {{Convert|{{sigfig|2.76604|3}}|AU|e6km|abbr=unit}}
| eccentricity = {{val|{{sigfig|0.0785010|3}}}}
| period = {{ubl|{{sigfig|4.60041|3}} [[Julian year (astronomy)|yr]]|{{val|{{sigfig|1680.300|3}}|u=d}}}}
| synodic_period = {{ubl|{{sigfig|1.278|3}} [[Julian year (astronomy)|yr]]|{{sigfig|466.6|4}} [[Julian day|d]]<ref>{{Cite book |title=A Journal of Natural Philosophy, Chemistry, and the Arts |date=1802 |language=en |chapter=On The New Planet Ceres |access-date=29 May 2022 |chapter-url=https://books.google.com/books?id=81_YWtSQUhcC&pg=PA52 |archive-date=29 May 2022 |archive-url=https://web.archive.org/web/20220529201716/https://books.google.com/books?id=81_YWtSQUhcC&pg=PA52 |url-status=live }}</ref>}}
| inclination = {{ubl|{{val|{{sigfig|10.58769|3}}|u=°}} to [[ecliptic]]|9.20° to [[invariable plane]]<ref name="Souami_Souchay_2012">{{Cite journal |last1=Souami |first1=D. |last2=Souchay |first2=J. |date=July 2012 |title=The solar system's invariable plane |journal=Astronomy & Astrophysics |volume=543 |page=11 |bibcode=2012A&A...543A.133S |doi=10.1051/0004-6361/201219011 |id=A133 |doi-access=free}}</ref>}}
| arg_peri = {{val|{{sigfig|73.63704|3}}|u=°}}
| asc_node = {{val|{{sigfig|80.26860|3}}|u=°}}
| mean_anomaly = {{val|{{sigfig|291.37560|4}}|ul=°}}
| avg_speed = {{val|{{sigfig|17.905|3}}|u=km/s}}
| p_orbit_ref = <ref name="Ceres-POE">{{Cite web |title=AstDyS-2 Ceres Synthetic Proper Orbital Elements |url=https://newton.spacedys.com/astdys/index.php?pc=1.1.6&n=1 |url-status=live |archive-url=https://web.archive.org/web/20111121225850/http://hamilton.dm.unipi.it/astdys/index.php?pc=1.1.6&n=1 |archive-date=21 November 2011 |access-date=1 October 2011 |publisher=Department of Mathematics, University of Pisa, Italy}}</ref>
| p_semimajor = {{val|{{sigfig|2.7670962|3}}}}
| p_eccentricity = {{val|{{sigfig|0.1161977|3}}}}
| p_inclination = {{val|{{sigfig|9.6474122|3}}|u=°}}
| p_mean_motion = {{sigfig|78.193318|3}}
| perihelion_rate = {{val|{{sigfig|54.070272|3}}}}
| node_rate = {{val|{{sigfig|-59.170034|3}}}}
| satellites = [[Dawn (spacecraft)|''Dawn'']] (derelict space probe)
| allsatellites = yes
| dimensions = (966.2 × 962.0 × 891.8)<br />± 0.2 km<ref name="Ermakov2017">{{cite journal |last1=Ermakov |first1=A. I. |last2=Fu |first2=R. R. |last3=Castillo-Rogez |first3=J. C. |last4=Raymond |first4=C. A. |last5=Park |first5=R. S. |last6=Preusker |first6=F. |last7=Russell |first7=C. T. |last8=Smith |first8=D. E. |last9=Zuber |first9=M. T. |title=Constraints on Ceres' Internal Structure and Evolution From Its Shape and Gravity Measured by the Dawn Spacecraft |journal=Journal of Geophysical Research: Planets |date=November 2017 |volume=122 |issue=11 |pages=2267–2293 |doi=10.1002/2017JE005302|bibcode=2017JGRE..122.2267E |s2cid=133739176 |doi-access=free }}</ref>
| mean_radius = {{val|469.7|0.1|u=km}}<ref name="Ermakov2017"/> (291.9 mi)
| surface_area = {{nowrap|{{val|fmt=commas|2772368|u=km2}}}}{{refn|group=lower-alpha|name="known parameters"|Calculated based on known parameters:
* Surface area: 4πr{{sup|2}}
* Surface gravity: {{sfrac|GM|r{{sup|2}}}}
* Escape velocity: {{radic|{{sfrac|2GM|r}}}}
* Rotation velocity: {{sfrac|circumference|rotation period}}}}
| volume = {{val|fmt=commas|434000000|u=km3}}<ref name="Park2018"/>
| mass = {{ubl|{{val|9.38392|0.00005|e=20|u=kg}}<ref name="Park2018"/>|{{val|0.00016|u=[[Earth mass|Earths]]}}|0.0128 [[Moon]]s}}
| density = {{val|2.1616|0.0025|u=g/cm3}}<ref name="Park2018">{{cite journal |last1=Park |first1=R.S. |last2=Vaughan |first2=A.T. |last3=Konopliv |first3=A.S. |last4=Ermakov |first4=A.I. |last5=Mastrodemos |first5=N. |last6=Castillo-Rogez |first6=J.C. |last7=Joy |first7=S.P. |last8=Nathues |first8=A. |last9=Polanskey |first9=C.A. |last10=Rayman |first10=M.D. |last11=Riedel |first11=J.E. |last12=Raymond |first12=C.A. |last13=Russell |first13=C.T. |last14=Zuber |first14=M.T. |title=High-resolution shape model of Ceres from stereophotoclinometry using Dawn Imaging Data |journal=Icarus |date=February 2019 |volume=319 |pages=812–827 |doi=10.1016/j.icarus.2018.10.024|bibcode=2019Icar..319..812P |s2cid=126268402 }}</ref>
| surface_grav = {{cvt|0.284|m/s2|g0|lk=out}}{{refn|group=lower-alpha|name="known parameters"}}
| moment_of_inertia_factor = {{val|0.36|0.15}}<ref name="Mao2018">{{Cite journal |last1=Mao |first1=X. |last2=McKinnon |first2=W. B. |year=2018 |title=Faster paleospin and deep-seated uncompensated mass as possible explanations for Ceres' present-day shape and gravity |journal=Icarus |volume=299 |pages=430–442 |bibcode=2018Icar..299..430M |doi=10.1016/j.icarus.2017.08.033}}</ref>{{refn|The value given for Ceres is the mean moment of inertia, which is thought to better represent its interior structure than the polar moment of inertia, due to its high polar flattening.<ref name="Park2016" />|group=lower-alpha}} (estimate)
| escape_velocity = {{V2|0.938|469.7|3}} km/s{{refn|group=lower-alpha|name="known parameters"}}
{{val|{{sigfig|1140.89|4}}|u=mph}}
| sidereal_day = {{val|9.074170|0.000001|u=h}}<ref name="jpl_sbdb" />
| rot_velocity = {{val|92.61|u=m/s}}{{refn|group=lower-alpha|name="known parameters"}}
| right_asc_north_pole = 291.42744°<ref name="Icarus2017">{{Cite journal |last1=Konopliv |first1=A.S. |last2=Park |first2=R.S. |last3=Vaughan |first3=A.T. |last4=Bills |first4=B.G. |last5=Asmar |first5=S.W. |last6=Ermakov |first6=A.I. |last7=Rambaux |first7=N. |last8=Raymond |first8=C.A. |last9=Castillo-Rogez |first9=J.C. |last10=Russell |first10=C.T. |last11=Smith |first11=D.E. |year=2018 |title=The Ceres gravity field, spin pole, rotation period and orbit from the Dawn radiometric tracking and optical data |journal=Icarus |volume=299 |pages=411–429 |bibcode=2018Icar..299..411K |doi=10.1016/j.icarus.2017.08.005 |last12=Zuber |first12=M.T.}}</ref>
| declination = 66.76033°<ref name="SPICE">{{Cite web |title=Asteroid Ceres P_constants (PcK) SPICE kernel file |url=http://naif.jpl.nasa.gov/pub/naif/DAWN/kernels/pck/dawn_ceres_v06.tpc |url-status=live |archive-url=https://web.archive.org/web/20200728153501/https://naif.jpl.nasa.gov/pub/naif/DAWN/kernels/pck/dawn_ceres_v06.tpc |archive-date=28 July 2020 |access-date=8 September 2019 |publisher=NASA Navigation and Ancillary Information Facility}}</ref>
| axial_tilt = ≈4°<ref name="Schorghofer2016" />
| albedo = {{val|0.090|0.0033}} (V-band)<ref name="Li2006" />
| temp_name1 = [[Kelvin]]
| min_temp_1 = ≈110<ref name="Dawn2017" />
| mean_temp_1 = {{val|172.5|2}}
| max_temp_1 = {{val|235|4}}<ref>{{Cite journal |title=Surface temperature of dwarf planet Ceres: Preliminary results from Dawn |journal=46th Lunar and Planetary Science Conference |first1=F.|last1=Tosi|first2=M. T.|last2=Capria|display-authors=etal|year=2015|page=11960 |bibcode=2015EGUGA..1711960T }}</ref>
| spectral_type = [[C-type asteroid|C]]<ref name="Rivkin2006">{{Cite journal |last1=Rivkin |first1=A. S. |last2=Volquardsen, E. L. |last3=Clark, B. E. |year=2006 |title=The surface composition of Ceres: Discovery of carbonates and iron-rich clays |url=http://irtfweb.ifa.hawaii.edu/~elv/icarus185.563.pdf |url-status=live |journal=Icarus |volume=185 |issue=2 |pages=563–567 |bibcode=2006Icar..185..563R |doi=10.1016/j.icarus.2006.08.022 |archive-url=https://web.archive.org/web/20071128201130/http://irtfweb.ifa.hawaii.edu/~elv/icarus185.563.pdf |archive-date=28 November 2007 |access-date=8 December 2007}}</ref>
| magnitude = {{ubl
 |7.6<ref name="skyand">{{Cite web |title=Let's Get Serious About Ceres |url=https://skyandtelescope.org/observing/celestial-objects-to-watch/lets-get-serious-about-ceres/|access-date=25 July 2022|last=King|first=Bob|date=5 August 2015 |publisher=[[Sky & Telescope]]}}</ref>
 | 9.27 (July 2021)<ref name="AstDys-object" />
 }}
| abs_magnitude = {{val|3.35}}<ref name="jpl_sbdb" />
| angular_size = 0.854″ <!--Horizons 1636-Feb-11--> to 0.339″
}}

'''Ceres''' is a [[dwarf planet]] in the main [[asteroid belt]] between the orbits of Mars and Jupiter. It was the first object identified in the asteroid belt, discovered on 1 January 1801 by [[Giuseppe Piazzi]] at [[Palermo Astronomical Observatory]] in Sicily, and announced as a new [[planet]]. Ceres was later classified as an asteroid, and then more recently as the only confirmed dwarf planet within the asteroid belt, and the largest without a moon. It is also the only recognized dwarf planet in the solar system whose orbit lies within that of Neptune. In the [[minor-planet number|minor planet numbering system]], its designation is '''1 Ceres''' or '''(1) Ceres'''.

Ceres's diameter is about a quarter that of the Moon. Its small size means that even at its brightest it is too dim to be seen by the naked eye, except under extremely dark skies. Its [[apparent magnitude]] ranges from 6.7 to 9.3, peaking at [[Opposition (astronomy)|opposition]] (when it is closest to Earth) once every 15- to 16-month [[synodic period]]. As a result, its surface features are barely visible even with the most powerful telescopes, and little was known about it until the robotic [[NASA]] spacecraft [[Dawn (spacecraft)|''Dawn'']] approached Ceres for its orbital mission in 2015.

''Dawn'' found Ceres's surface to be a mixture of water, ice, and [[hydrate]]d minerals such as [[carbonate mineral|carbonates]] and clay. Gravity data suggest Ceres to be partially [[Planetary differentiation|differentiated]] into a muddy (ice–rock) [[mantle (geology)|mantle/core]] and a less [[density|dense]], but stronger [[Crust (geology)|crust]] that is at most thirty percent ice by volume. Although Ceres likely has an [[internal ocean]] of liquid water, [[brine]]s still flow through the outer mantle and reach the surface, allowing [[cryovolcano]]es such as [[Ahuna Mons]] to form roughly every fifty million years. This makes Ceres the closest known cryovolcanically active body to the Sun. Ceres has an extremely tenuous and transient atmosphere of water vapour, vented from localised sources on its surface.

== History ==
In the years between the acceptance of [[heliocentrism]] in the 18th century and the discovery of [[Neptune]] in 1846, several astronomers argued that mathematical laws predicted the existence of a hidden or missing planet between the orbits of [[Mars]] and [[Jupiter]]. In 1596, [[theoretical astronomy|theoretical astronomer]] [[Johannes Kepler]] believed that the ratios between planetary orbits would conform to "[[Musica universalis|God's design]]" only with the addition of two planets: one between Jupiter and Mars and one between Venus and Mercury.<ref name="hoskin" /> Other theorists, such as [[Immanuel Kant]], pondered whether the gap had been created by the gravity of Jupiter; in 1761, astronomer and mathematician [[Johann Heinrich Lambert]] asked: "And who knows whether already planets are missing which have departed from the vast space between Mars and Jupiter? Does it then hold of celestial bodies as well as of the Earth, that the stronger chafe the weaker, and are Jupiter and Saturn destined to plunder forever?"<ref name="hoskin" />

In 1772, German astronomer [[Johann Elert Bode]], citing [[Johann Daniel Titius]], published a formula later known as the [[Titius–Bode law]] that appeared to predict the orbits of the known planets but for an unexplained gap between Mars and Jupiter.<ref name="hoskin" /><ref name="Hogg1948">{{Cite journal |last=Hogg |first=Helen Sawyer |year=1948 |title=The Titius-Bode Law and the Discovery of Ceres |journal=Journal of the Royal Astronomical Society of Canada |volume=242 |pages=241–246 |bibcode=1948JRASC..42..241S }}</ref> This formula predicted that there ought to be another planet with an orbital radius near 2.8 [[astronomical unit]]s (AU), or 420&nbsp;million&nbsp;km, from the Sun.<ref name="Hogg1948" /> The Titius–Bode law gained more credence with [[William Herschel]]'s 1781 discovery of [[Uranus]] near the predicted distance for a planet beyond [[Saturn]].<ref name="hoskin" /> In 1800, a group headed by [[Franz Xaver von Zach]], editor of the German astronomical journal {{lang|de|Monatliche Correspondenz}} (''[[Monthly Correspondence]]''), sent requests to twenty-four experienced astronomers, whom he dubbed the "[[celestial police]]",<ref name="Hogg1948" /> asking that they combine their efforts and begin a methodical search for the expected planet.<ref name="Hogg1948" /> Although they did not discover Ceres, they later found the [[asteroid]]s [[2 Pallas|Pallas]], [[3 Juno|Juno]], and [[4 Vesta|Vesta]].<ref name="Hogg1948" />

=== Discovery ===
One of the astronomers selected for the search was [[Giuseppe Piazzi]], a Catholic priest at the academy of [[Palermo|Palermo, Sicily]]. Before receiving his invitation to join the group, Piazzi discovered Ceres on 1 January 1801.<ref name="NASA-20160126">{{Cite web |last=Landau |first=Elizabeth |date=26 January 2016 |title=Ceres: Keeping Well-Guarded Secrets for 215 Years |url=http://www.jpl.nasa.gov/news/news.php?feature=4824 |url-status=live |archive-url=https://web.archive.org/web/20190524043553/https://www.jpl.nasa.gov/news/news.php?feature=4824 |archive-date=24 May 2019 |access-date=26 January 2016 |website=NASA}}</ref> He was searching for "the 87th [star] of the Catalogue of the Zodiacal stars of [[Nicolas-Louis de Lacaille|Mr la Caille]]", but found that "it was preceded by another".<ref name="hoskin">{{Cite web |last=Hoskin |first=Michael |date=26 June 1992 |title=Bode's Law and the Discovery of Ceres |url=http://www.astropa.unipa.it/HISTORY/hoskin.html |archive-url=https://web.archive.org/web/20071116022100/http://www.astropa.unipa.it/HISTORY/hoskin.html |archive-date=16 November 2007 |access-date=5 July 2007 |publisher=Observatorio Astronomico di Palermo "Giuseppe S. Vaiana"}}</ref> Instead of a star, Piazzi had found a moving starlike object, which he first thought was a comet.<ref name="Forbes1971">{{Cite journal |last=Forbes |first=Eric G. |year=1971 |title=Gauss and the Discovery of Ceres |journal=Journal for the History of Astronomy |volume=2 |issue=3 |pages=195–199 |bibcode=1971JHA.....2..195F |doi=10.1177/002182867100200305 }}</ref> Piazzi observed Ceres twenty-four times, the final sighting occurring on 11 February 1801, when illness interrupted his work. He announced his discovery on 24 January 1801 in letters to two fellow astronomers, his compatriot [[Barnaba Oriani]] of [[Milan]] and Bode in [[Berlin]].<ref>{{Cite book |last=Cunningham |first=Clifford J. |url=https://books.google.com/books?id=CXdMPwAACAAJ |title=The first asteroid: Ceres, 1801–2001 |publisher=Star Lab Press |year=2001 |isbn=978-0-9708162-1-4 |access-date=23 October 2015 |archive-url=https://web.archive.org/web/20160529144326/https://books.google.com/books?id=CXdMPwAACAAJ |archive-date=29 May 2016 |url-status=live}}</ref> He reported it as a comet, but "since its movement is so slow and rather uniform, it has occurred to me several times that it might be something better than a comet".<ref name="hoskin" /> In April, Piazzi sent his complete observations to Oriani, Bode, and French astronomer [[Jérôme Lalande]]. The information was published in the September 1801 issue of the ''Monthly Correspondence''.<ref name="Forbes1971" />

By this time, the apparent position of Ceres had changed (primarily due to Earth's motion around the Sun) and was too close to the Sun's glare for other astronomers to confirm Piazzi's observations. Towards the end of the year, Ceres should have been visible again, but after such a long time, it was difficult to predict its position. To recover Ceres, the mathematician [[Carl Friedrich Gauss]], then twenty-four years old, developed an [[Gauss's method|efficient method]] of [[orbit determination]].<ref name="Forbes1971" /> He predicted the path of Ceres within a few weeks and sent his results to von Zach. On 31 December 1801, von Zach and fellow celestial policeman [[Heinrich Wilhelm Matthias Olbers|Heinrich W. M. Olbers]] found Ceres near the predicted position and continued to record its position.<ref name="Forbes1971" /> At 2.8 AU from the Sun, Ceres appeared to fit the Titius–Bode law almost perfectly; when Neptune was discovered in 1846, eight AU closer than predicted, most astronomers concluded that the law was a coincidence.<ref>{{Cite book |last=Nieto |first=Michael Martin |url=https://books.google.com/books?id=NneoBQAAQBAJ&q=bode+law+neptune+coincidence+1846&pg=PP1 |title=The Titius-Bode Law of Planetary Distances: Its History and Theory |publisher=Pergamon Press |year=1972 |isbn=978-1-4831-5936-2 |access-date=23 September 2021 |archive-url=https://web.archive.org/web/20210929081229/https://books.google.co.uk/books?hl=en&lr=&id=NneoBQAAQBAJ&oi=fnd&pg=PP1&dq=bode+law+neptune+coincidence+1846&ots=LIplNAOXco&sig=qAF2y5xXTivecmSP_fjGCDA9Sx4&redir_esc=y |archive-date=29 September 2021 |url-status=live}}</ref>

The early observers were able to calculate the size of Ceres only to within an [[order of magnitude]]. Herschel underestimated its diameter at {{cvt|260|km|mi}} in 1802; in 1811, German astronomer [[Johann Hieronymus Schröter]] overestimated it at {{cvt|2,613|km|mi}}.<ref name="hughues">{{Cite journal |last=Hughes |first=David W |year=1994 |title=The Historical Unravelling of the Diameters of the First Four Asteroids |journal=Quarterly Journal of the Royal Astronomical Society |volume=35 |pages=331–344 |bibcode=1994QJRAS..35..331H }}</ref> In the 1970s, infrared [[Photometry (astronomy)|photometry]] enabled more accurate measurements of its [[albedo]], and Ceres's diameter was determined to within ten percent of its true value of {{cvt|939|km|mi}}.<ref name="hughues" />

=== Name and symbol ===
Piazzi's proposed name for his discovery was ''Ceres Ferdinandea'': ''Ceres'' after the [[Ceres (mythology)|Roman goddess of agriculture]], whose earthly home, and oldest temple, lay in Sicily; and ''Ferdinandea'' in honour of Piazzi's monarch and patron, King [[Ferdinand I of the Two Sicilies|Ferdinand&nbsp;III]] of [[Kingdom of Sicily|Sicily]].<ref name="Forbes1971" /> The latter was not acceptable to other nations and was dropped. Before von Zach's recovery of Ceres in December 1801, von Zach referred to the planet as ''[[Hera]],'' and Bode referred to it as ''[[Juno (mythology)|Juno]]''. Despite Piazzi's objections, those names gained currency in Germany before the object's existence was confirmed. Once it was, astronomers settled on Piazzi's name.<ref>{{Cite book |last1=Foderà Serio, G. |title=Asteroids III |last2=Manara, A. |last3=Sicoli, P. |publisher=University of Arizona Press |year=2002 |editor-last=W. F. Bottke Jr. |location=Tucson |pages=17–24 |chapter=Giuseppe Piazzi and the Discovery of Ceres |access-date=25 June 2009 |editor-last2=A. Cellino |editor-last3=P. Paolicchi |editor-last4=R. P. Binzel |chapter-url=http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3027.pdf |archive-url=https://web.archive.org/web/20120416221621/http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3027.pdf |archive-date=16 April 2012 |url-status=live}}</ref>

The adjectival forms of ''Ceres'' are ''Cererian''<ref>{{Cite book |last=Rüpke, Jörg |url=https://books.google.com/books?id=FRRLOltuxDcC&pg=PT90 |title=A Companion to Roman Religion |publisher=John Wiley and Sons |year=2011 |isbn=978-1-4443-4131-7 |pages=51–52 |author-link=Jörg Rüpke |access-date=23 October 2015 |archive-url=https://web.archive.org/web/20151115202651/https://books.google.com/books?id=FRRLOltuxDcC&pg=PT90 |archive-date=15 November 2015 |url-status=live}}</ref><ref>{{Cite web |date=21 September 2012 |title=Dawn Spacecraft Finds Traces of Water on Vesta |url=https://scitechdaily.com/dawn-spacecraft-finds-traces-of-water-on-vesta/ |url-status=live |archive-url=https://web.archive.org/web/20210923202702/https://scitechdaily.com/dawn-spacecraft-finds-traces-of-water-on-vesta/ |archive-date=23 September 2021 |access-date=23 September 2021 |work=Sci-Tech Daily}}</ref> and ''Cererean'',<ref>{{cite book|first1=A. S. |last1=Rivkin |display-authors=etal |year=2012 |chapter=The Surface Composition of Ceres |editor-first1=Christopher |editor-last1=Russell |editor-first2=Carol |editor-last2=Raymond |title=The Dawn Mission to Minor Planets 4 Vesta and 1 Ceres |page=109 |publisher=Springer |isbn=978-1-4614-4902-7}}</ref> both pronounced {{IPAc-en|s|ᵻ|ˈ|r|ɪər|i|ə|n}}.<ref>{{cite book |author=Thornton |first=William Thomas |title=Word For Word From Horace |publisher=Nabu Press |year=2012 |isbn=978-1-279-56080-8 |page=314 |chapter=Epode 16 |orig-date=1878}}</ref><ref>{{cite book |author=Booth |first=W. |url=https://books.google.com/books?id=P6jPtkMsj8UC |title=Flowers of Roman Poesy |publisher=Harvard University |year=1823}}</ref> [[Cerium]], a [[rare-earth element]] discovered in 1803, was named after Ceres.<ref>{{Cite web |title=Cerium: historical information |url=http://www.webelements.com/cerium/history.html |url-status=live |archive-url=https://web.archive.org/web/20100409042237/http://www.webelements.com/cerium/history.html |archive-date=9 April 2010 |access-date=27 April 2007 |publisher=Adaptive Optics}}</ref>{{refn|In 1807 Klaproth tried to change the name of the element to ''cererium'', to avoid confusion with the root ''cēra'', 'wax' (as in ''cereous'', 'waxy'), but it did not catch on.<ref>{{Cite OED|Cerium}}</ref> |group="lower-alpha"}}

The old [[astronomical symbol]] of Ceres, still used in astrology, is a [[sickle]], ⟨⚳⟩.<ref name="Forbes1971" /><ref>{{Cite web |last=JPL/NASA |date=22 April 2015 |title=What is a Dwarf Planet? |url=https://www.jpl.nasa.gov/infographics/what-is-a-dwarf-planet |access-date=19 January 2022 |website=Jet Propulsion Laboratory |archive-date=8 December 2021 |archive-url=https://web.archive.org/web/20211208181916/https://www.jpl.nasa.gov/infographics/what-is-a-dwarf-planet |url-status=live }}</ref> The sickle was one of the classical symbols of the goddess Ceres and was suggested, apparently independently, by von Zach and Bode in 1802.<ref>{{cite book|first=Clifford |last=Cunningham |year=2015 |title=Discovery of the First Asteroid, Ceres |publisher=Springer Intl. |pages=69, 164, 206 |isbn=978-3-319-21777-2 |oclc=1100952738}}</ref> It is similar in form to the symbol ⟨♀⟩ (a circle with a small cross beneath) of the planet Venus, but with a break in the circle. It had various minor graphic variants, including a reversed form [[File:Ceres 'C' symbol.svg|12px]] typeset as a 'C' (the initial letter of the name ''Ceres'') with a plus sign. The generic asteroid symbol of a numbered disk, ①, was introduced in 1867 and quickly became the norm.<ref name="Forbes1971" /><ref>{{Cite journal |last=Gould |first=B. A. |author-link=Benjamin Apthorp Gould |year=1852 |title=On the symbolic notation of the asteroids |journal=Astronomical Journal |volume=2 |issue=34 |page=80 |bibcode=1852AJ......2...80G |doi=10.1086/100212}}</ref>

=== Classification ===
{{Multiple image
| direction         = horizontal
| align             = center
| width             = 300
| image1            = Ceres, Earth & Moon size comparison.jpg
| alt1              = Ceres (bottom left), the Moon and Earth, shown to scale
| caption1          = Ceres (bottom left), the [[Moon]] and Earth, shown to scale
| image2            = The Four Largest Asteroids.jpg
| alt2              = Relative sizes of the four largest asteroids. Ceres is furthest left.
| caption2          = Relative mean diameters of the four largest [[minor planet]]s in the [[asteroid belt]] ([[dwarf planet]] Ceres at left)
| total_width       = 
}}
{{Pie chart
|value1 = 938
|label1 = 1 Ceres
|value2 = 259
|label2 = [[4 Vesta]]
|value3 = 204
|label3 = [[2 Pallas]]
|value4 = 87
|label4 = [[10 Hygiea]]
|value5 = 35
|label5 = [[704 Interamnia]]
|value6 = 30
|label6 = [[15 Eunomia]]
|value7 = 841<!--total 2394x18kg-->
|label7 = other ≈
|legend=true
|caption=The mass of 1 Ceres (dark green) compared to other large asteroids and the remainder of the Main Belt. The unit of mass is{{X10^|18}} kg.
|autoscale=true
|radius=125
|border=no
}}
The categorisation of Ceres has changed more than once and has been the subject of some disagreement. Bode believed Ceres to be the "missing planet" he had proposed to exist between Mars and Jupiter.<ref name="hoskin" /> Ceres was assigned a planetary symbol and [[Definition of planet#Minor planets|remained listed as a planet]] in astronomy books and tables (along with Pallas, Juno, and Vesta) for over half a century.<ref name="Hilton" />

As other objects were discovered in the neighbourhood of Ceres, astronomers began to suspect that it represented the first of a new class of objects.<ref name="hoskin" /> When Pallas was discovered in 1802, Herschel introduced the term ''asteroid'' ("star-like") for these bodies,<ref name="Hilton">{{Cite web |last=Hilton |first=James L. |date=17 September 2001 |title=When Did the Asteroids Become Minor Planets? |url=http://aa.usno.navy.mil/faq/docs/minorplanets.php |archive-url=https://web.archive.org/web/20071106124911/http://aa.usno.navy.mil/faq/docs/minorplanets.php |archive-date=6 November 2007 |access-date=16 August 2006 |publisher=US Naval Observatory}}</ref> writing that "they resemble small stars so much as hardly to be distinguished from them, even by very good telescopes".<ref>{{Cite journal |last=Herschel |first=William |author-link=William Herschel |date=6 May 1802 |title=Observations on the two lately discovered celestial Bodies |journal=Philosophical Transactions of the Royal Society of London |volume=92 |pages=213–232 |bibcode=1802RSPT...92..213H |doi=10.1098/rstl.1802.0010 |jstor=107120 |s2cid=115664950}}</ref> In 1852 [[Johann Franz Encke]], in the ''[[Berliner Astronomisches Jahrbuch]]'', declared the traditional system of granting planetary symbols too cumbersome for these new objects and introduced a new method of placing numbers before their names in order of discovery. The numbering system initially began with the fifth asteroid, [[5 Astraea|5&nbsp;Astraea]], as number&nbsp;1, but in 1867, Ceres was adopted into [[Minor-planet designation|the new system]] under the name 1&nbsp;Ceres.<ref name="Hilton" />

By the 1860s, astronomers widely accepted that a fundamental difference existed between the major planets and asteroids such as Ceres, though the word "planet" had [[Definition of planet|yet to be precisely defined]].<ref name="Hilton" /> In the 1950s, scientists generally stopped considering most asteroids as planets, but Ceres sometimes retained its status after that because of its planet-like geophysical complexity.<ref name=metzger19>{{cite journal |last1=Metzger |first1=Philip T. |author-link1=Philip T. Metzger |last2=Sykes |first2=Mark V. |last3=Stern |first3=Alan |last4=Runyon |first4=Kirby |year=2019 |title=The Reclassification of Asteroids from Planets to Non-Planets |journal=Icarus |volume=319 |pages=21–32 |doi=10.1016/j.icarus.2018.08.026|arxiv=1805.04115 |bibcode=2019Icar..319...21M |s2cid=119206487 }}</ref> Then, in 2006, the debate surrounding [[Pluto]] led to calls for a definition of "planet", and the possible reclassification of Ceres, perhaps even its general reinstatement as a planet.<ref>{{Cite news |last=Connor |first=Steve |date=16 August 2006 |title=Solar system to welcome three new planets |work=The New Zealand Herald |url=https://www.nzherald.co.nz/technology/solar-system-to-welcome-three-new-planets/KQJAEQL22GMH4Y2ESZA7YIHBTM/ |url-status=live |access-date=19 July 2021 |archive-url=https://web.archive.org/web/20210719210858/https://www.nzherald.co.nz/technology/solar-system-to-welcome-three-new-planets/KQJAEQL22GMH4Y2ESZA7YIHBTM/ |archive-date=19 July 2021}}</ref> A proposal before the [[International Astronomical Union]] (IAU), the global body responsible for astronomical nomenclature and classification, defined a planet as "a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet".<ref>{{Cite web |last=Gingerich |first=Owen |author-link=Owen Gingerich |display-authors=etal |date=16 August 2006 |title=The IAU draft definition of "Planet" and "Plutons" |url=http://www.iau.org/iau0601.424.0.html |archive-url=https://web.archive.org/web/20080827210426/http://www.iau.org/iau0601.424.0.html |archive-date=27 August 2008 |access-date=27 April 2007 |publisher=IAU}}</ref> Had this resolution been adopted, it would have made Ceres the fifth planet in order from the Sun,<ref>{{Cite web |date=16 August 2006 |title=The IAU Draft Definition of Planets and Plutons |url=http://www.spacedaily.com/reports/The_IAU_Draft_Definition_Of_Planets_And_Plutons_999.html |url-status=live |archive-url=https://web.archive.org/web/20090906072954/http://www.spacedaily.com/reports/The_IAU_Draft_Definition_Of_Planets_And_Plutons_999.html |archive-date=6 September 2009 |access-date=27 April 2007 |publisher=SpaceDaily}}</ref> but on 24 August 2006 the assembly adopted the additional requirement that a planet must have "[[Clearing the neighbourhood|cleared the neighbourhood]] around its orbit". Ceres is not a planet because it does not dominate its orbit, sharing it as it does with the thousands of other asteroids in the asteroid belt and constituting only about forty per cent of the belt's total mass.<ref>{{cite journal |last=Pitjeva |first=E.V. |author-link=Elena V. Pitjeva |year=2018 |title=Masses of the main asteroid belt and the Kuiper belt from the motions of planets and spacecraft |journal=[[Solar System Research]] |volume=44 |issue=8–9 |pages=554–566 |arxiv=1811.05191 |doi=10.1134/S1063773718090050 |bibcode= 2018AstL...44..554P |s2cid=119404378 }}</ref> Bodies that met the first proposed definition but not the second, such as Ceres, were instead classified as [[dwarf planet]]s.<ref>{{Cite web |title=In Depth &#124; Ceres |url=https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/in-depth |url-status=live |archive-url=https://web.archive.org/web/20190421175656/https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/in-depth/ |archive-date=21 April 2019 |access-date=21 April 2019 |website=NASA Solar System Exploration|date=9 November 2017 }}</ref> Planetary geologists still often ignore this definition and consider Ceres to be a planet anyway.<ref name=metzger22>{{cite journal |last1=Metzger |first1=Philip T. |author-link1=Philip T. Metzger |last2=Grundy |first2=W. M. |first3=Mark V. |last3=Sykes |first4=Alan |last4=Stern |first5=James F. |last5=Bell III |first6=Charlene E. |last6=Detelich |first7=Kirby |last7=Runyon |first8=Michael |last8=Summers |year=2022 |title=Moons are planets: Scientific usefulness versus cultural teleology in the taxonomy of planetary science |journal=Icarus |volume=374 |article-number=114768 |doi=10.1016/j.icarus.2021.114768 |arxiv=2110.15285 |bibcode=2022Icar..37414768M }}</ref>

Ceres is designated as a dwarf planet and an asteroid. A NASA webpage states that [[4 Vesta|Vesta]], the belt's second-largest object, is the largest asteroid.<ref>{{cite web |title=One mission, two remarkable destinations | department=Science | date=26 October 2017 | website=[[NASA]] (science.nasa.gov) |url=https://science.nasa.gov/solar-system/asteroids/ |url-status=live |archive-url=https://web.archive.org/web/20200717143754/https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/overview/?page=0&per_page=40&order=name+asc&search=&condition_1=101:parent_id&condition_2=asteroid:body_type:ilike |archive-date=17 July 2020 |access-date=14 July 2020 |quote=Asteroids range in size from Vesta – the largest at about 329&nbsp;miles (530&nbsp;km) in diameter&nbsp;... }}</ref> The IAU has been equivocal on the subject,<ref name=kenneth>{{cite book |last=Lang |first=Kenneth |year=2011 |title=The Cambridge Guide to the Solar System | publisher=Cambridge University Press |isbn=978-1-139-49417-5 | pages=372, 442 |url=https://books.google.com/books?id=S4xDhVCxAQIC&pg=PR5 |url-status=live |via=Google |access-date=27 July 2019 |archive-url=https://web.archive.org/web/20200726125744/https://books.google.com/books?id=S4xDhVCxAQIC&pg=PR5 |archive-date=26 July 2020 }}</ref><ref name=IAU-QA>{{cite web |title=Question and answers&nbsp;2 |website=iau.org |publisher=[[International Astronomical Union]] |url=https://www.iau.org/public/themes/pluto/ |url-status=live |access-date=31 January 2008 |archive-url=https://web.archive.org/web/20160130022141/http://www.iau.org/public/themes/pluto/ |archive-date=30 January 2016 |quote=Ceres is (or now we can say it was) the largest asteroid&nbsp;... There are many other asteroids that can come close to the orbital path of Ceres.}}</ref>{{failed verification|date=October 2025}} though its [[Minor Planet Center]], the organisation charged with cataloguing such objects, notes that dwarf planets may have dual designations,<ref>{{cite web |last=Spahr |first=T.B. |author-link=Timothy B. Spahr |date=7 September 2006 |title=Editorial notice |series=MPEC 2006-R19 |website=minorplanetcenter.net |publisher=[[Minor Planet Center]] (MPC) |url=https://minorplanetcenter.net/mpec/K06/K06R19.html |url-status=live |archive-url=https://web.archive.org/web/20081010120050/http://cfa-www.harvard.edu/mpec/K06/K06R19.html |archive-date=10 October 2008 |access-date=31 January 2008 |quote=the numbering of 'dwarf planets' does not preclude their having dual designations in possible separate catalogues of such bodies. }}</ref> and the joint IAU / [[USGS]] / NASA ''Gazetteer'' categorises Ceres as both asteroid and a dwarf planet.<ref>{{cite web |title=Target: Ceres |department=Gazetteer of Planetary Nomenclature |website=planetarynames.wr.usgs.gov |publisher=[[International Astronomical Union]] / [[USGS Astrogeology Science Center]] / [[National Aeronautics and Space Administration]] |url=https://planetarynames.wr.usgs.gov/Page/CERES/target |url-status=live |archive-url=https://web.archive.org/web/20171013231505/https://planetarynames.wr.usgs.gov/Page/CERES/target |archive-date=13 October 2017 |access-date=27 September 2021}}</ref>

== Orbit ==
[[File:Ceres Orbit c.png|thumb|upright=1.5|right|Orbits of Ceres (red, inclined) along with Jupiter and the inner planets (white and grey). The upper diagram shows Ceres's orbit from top down. The bottom diagram is a side view showing Ceres's orbital inclination to the [[ecliptic]]. Lighter shades indicate above the ecliptic; darker indicate below.]]

Ceres follows an orbit between Mars and Jupiter, near the middle of the asteroid belt, with an [[orbital period]] of 4.6 Earth years.<ref name="jpl_sbdb" /> Compared to other planets and dwarf planets, Ceres's orbit is moderately tilted relative to that of Earth; its [[orbital inclination|inclination]] (''i'') is 10.6°, compared to 7° for [[Mercury (planet)|Mercury]] and 17° for Pluto. It is also slightly elongated, with an [[orbital eccentricity|eccentricity]] (''e'') = 0.08, compared to 0.09 for Mars.<ref name="jpl_sbdb" /> Ceres is the only widely accepted dwarf planet with an orbital period less than that of Neptune.<ref name="cerescomp" />

Ceres is not part of an [[asteroid family]], probably due to its large proportion of ice, as smaller bodies with the same composition would have [[Sublimation (phase transition)|sublimated]] to nothing over the age of the Solar System.<ref name="liebert" /> It was once thought to be a member of the [[Gefion family]],<ref name="Cellino">{{Cite book |last=Cellino, A. |title=Asteroids III |publisher=University of Arizona Press |year=2002 |pages=633–643 (Table on p. 636) |chapter=Spectroscopic Properties of Asteroid Families |bibcode=2002aste.book..633C |display-authors=etal |access-date=6 August 2011 |chapter-url=http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3018.pdf |archive-url=https://web.archive.org/web/20160328010330/http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3018.pdf |archive-date=28 March 2016 |url-status=live}}</ref> the members of which share similar [[proper orbital elements]], suggesting a common origin through an asteroid collision in the past. Ceres was later found to have a different composition from the Gefion family<ref name="Cellino" /> and appears to be an [[Interloper (asteroid)|interloper]], having similar orbital elements but not a common origin.<ref name="Kelley">{{Cite journal |last1=Kelley, M. S. |last2=Gaffey, M. J. |year=1996 |title=A Genetic Study of the Ceres (Williams #67) Asteroid Family |journal=Bulletin of the American Astronomical Society |volume=28 |page=1097 |bibcode=1996DPS....28.1009K}}</ref>

=== Resonances ===
Due to their small masses and large separations, objects within the asteroid belt rarely fall into gravitational [[Orbital resonance|resonances]] with each other.<ref name="Christou">{{Cite journal |last=Christou |first=A. A. |year=2000 |title=Co-orbital objects in the main asteroid belt |journal=[[Astronomy & Astrophysics]] |volume=356 |pages=L71–L74 |bibcode=2000A&A...356L..71C}}</ref> Nevertheless, Ceres is able to capture other asteroids into temporary 1:1 resonances (making them temporary [[Trojan (celestial body)|trojans]]), for periods from a few hundred thousand to more than two million years. Fifty such objects have been identified.<ref name="Christou2012">{{Cite journal |last1=Christou |first1=A. A. |last2=Wiegert |first2=P. |date=January 2012 |title=A population of Main Belt Asteroids co-orbiting with Ceres and Vesta |journal=Icarus |volume=217 |issue=1 |pages=27–42 |arxiv=1110.4810 |bibcode=2012Icar..217...27C |doi=10.1016/j.icarus.2011.10.016 }}</ref> Ceres is close to a 1:1 mean-motion orbital resonance with [[2 Pallas|Pallas]] (their proper orbital periods differ by 0.2%), but not close enough to be significant over astronomical timescales.<ref name="Kovačević">{{Cite journal |last=Kovačević |first=A. B. |year=2011 |title=Determination of the mass of Ceres based on the most gravitationally efficient close encounters |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=419 |issue=3 |pages=2725–2736 |arxiv=1109.6455 |bibcode=2012MNRAS.419.2725K |doi=10.1111/j.1365-2966.2011.19919.x|doi-access=free }}</ref>

== Rotation and axial tilt ==
[[File:Permanent Shadows on Ceres.webm|thumb|left|alt=image of Ceres, half in shadow and half out|Permanently shadowed regions capable of accumulating surface ice]]
The rotation period of Ceres (the Cererian day) is 9&nbsp;hours and 4&nbsp;minutes;<ref name="Schorghofer2016" /> the small equatorial crater of Kait is selected as its [[prime meridian]].<ref>{{cite web |author=Rayman |first=Marc |date=30 October 2015 |title=New Maps of Ceres Reveal Topography Surrounding Mysterious 'Bright Spots' |url=https://www.jpl.nasa.gov/blog/2015/10/new-maps-of-ceres-reveal-topography-surrounding-mysterious-bright-spots |access-date=13 September 2022 |publisher=NASA}}</ref> Ceres has an axial tilt of 4°,<ref name="Schorghofer2016" /> small enough for its polar regions to contain permanently shadowed craters that are expected to act as [[Cold trap (astronomy)|cold traps]] and accumulate water ice over time, similar to [[Lunar water#Trapping|what occurs on the Moon]] and [[Mercury (planet)#Surface conditions and exosphere|Mercury]]. About 0.14% of water molecules released from the surface are expected to end up in the traps, hopping an average of three times before escaping or being trapped.<ref name="Schorghofer2016">{{Cite journal |last1=Schorghofer |first1=N. |last2=Mazarico |first2=E. |last3=Platz |first3=T. |last4=Preusker |first4=F. |last5=Schröder |first5=S. E. |last6=Raymond |first6=C. A. |last7=Russell |first7=C. T. |date=6 July 2016 |title=The permanently shadowed regions of dwarf planet Ceres |journal=Geophysical Research Letters |volume=43 |issue=13 |pages=6783–6789 |bibcode=2016GeoRL..43.6783S |doi=10.1002/2016GL069368 |doi-access=free}}</ref>

''[[Dawn (spacecraft)|Dawn]]'', the first spacecraft to orbit Ceres, determined that the north polar axis points at right ascension 19&nbsp;h 25&nbsp;m 40.3&nbsp;s (291.418°), declination +66° 45' 50" (about 1.5 degrees from [[Delta Draconis]]), which means an axial tilt of 4°. This means that Ceres currently sees little to no seasonal variation in sunlight by latitude.<ref name="presentation">{{Cite web |last1=Russell |first1=C. T. |last2=Raymond |first2=C. A. |display-authors=etal |date=21 July 2015 |title=05. Dawn Explores Ceres Results from the Survey Orbit |url=https://nesf2015.arc.nasa.gov/sites/default/files/downloads/pdf/05.pdf |url-status=live |archive-url=https://web.archive.org/web/20150905125337/http://nesf2015.arc.nasa.gov/sites/default/files/downloads/pdf/05.pdf |archive-date=5 September 2015 |access-date=23 September 2021 |publisher=NASA}}</ref> Gravitational influence from Jupiter and Saturn over the course of the last three million years has triggered cyclical shifts in Ceres's axial tilt, ranging from two to twenty degrees, meaning that seasonal variation in sun exposure has occurred in the past, with the last period of seasonal activity estimated at 14,000 years ago. Those craters that remain in shadow during periods of maximum axial tilt are the most likely to retain water ice from eruptions or cometary impacts over the age of the Solar System.<ref>{{Cite web |year=2017 |title=Ice in Ceres' Shadowed Craters Linked to Tilt History |url=https://solarsystem.nasa.gov/news/572/ice-in-ceres-shadowed-craters-linked-to-tilt-history/ |url-status=live |archive-url=https://web.archive.org/web/20210515225206/https://solarsystem.nasa.gov/news/572/ice-in-ceres-shadowed-craters-linked-to-tilt-history/ |archive-date=15 May 2021 |access-date=15 May 2021 |website=NASA Solar System Exploration}}</ref>

== Geology ==
{{Main|Geology of Ceres|List of geological features on Ceres}}

[[File:Terrestrial planet size comp 2024.png|thumb|upright=1.4|Ceres to scale among the [[Inner Solar System]] [[planetary-mass object]]s, arranged by the order of their orbits outward from the Sun (from left: [[Mercury (planet)|Mercury]], [[Venus]],
[[Earth]], the [[Moon]], [[Mars]] and Ceres)]]
{{multiple image
| align             = right
| total_width       = 370
| image1            = Ceres Blender render.png
| caption1          = One side
| image2            = Ceres Blender render other side.png
| caption2          = Other side
| footer            = Ceres rendered with [[Blender (software)|Blender]]. The base colour map and [[Heightmap|height map]] are from [[NASA]] and [[United States Geological Survey|USGS]].
}}

Ceres is the largest asteroid in the main asteroid belt.<ref name="Rivkin2006" /> It has been classified as a [[C-type asteroid|C‑type]] or carbonaceous asteroid<ref name="Rivkin2006" /> and, due to the presence of clay minerals, as a [[G-type asteroid]].<ref name="Parker2002" /> It has a similar, but not identical, composition to that of [[carbonaceous chondrite]] meteorites.<ref>{{Cite journal |last1=McCord |first1=Thomas B. |last2=Zambon |first2=Francesca |date=15 January 2019 |title=The surface composition of Ceres from the Dawn mission |journal=Icarus |volume=318 |pages=2–13 |bibcode=2019Icar..318....2M |doi=10.1016/j.icarus.2018.03.004 }}</ref> It is an [[oblate spheroid]], with an equatorial diameter 8% larger than its polar diameter.<ref name="jpl_sbdb" /> Measurements from the ''Dawn'' spacecraft found a mean diameter of {{convert|939.4|km|abbr=on}}<ref name="jpl_sbdb" /> and a mass of {{val|9.38|e=20|u=kg}}.<ref name="Rayman20150528">{{Cite web |last=Rayman |first=Marc D. |date=28 May 2015 |title=Dawn Journal, 28 May 2015 |url=http://dawnblog.jpl.nasa.gov/2015/05/28/dawn-journal-may-28-2015/ |archive-url=https://web.archive.org/web/20150530075157/http://dawnblog.jpl.nasa.gov/2015/05/28/dawn-journal-may-28-2015/ |archive-date=30 May 2015 |access-date=29 May 2015 |publisher=[[Jet Propulsion Laboratory]]}}</ref> This gives Ceres a density of {{val|2.16|u=g/cm3}},<ref name="jpl_sbdb" /> suggesting that a quarter of its mass is water ice.<ref name="cerescomp">{{Cite web |last=Nola Taylor Redd |date=23 May 2018 |title=Ceres: The Smallest and Closest Dwarf Planet |url=https://www.space.com/22891-ceres-dwarf-planet.html |url-status=live |archive-url=https://web.archive.org/web/20210905112623/https://www.space.com/22891-ceres-dwarf-planet.html |archive-date=5 September 2021 |access-date=25 July 2021 |website=space.com}}</ref>

Ceres makes up 40% of the estimated {{val|2394|5|e=18|u=kg}} mass of the asteroid belt, and it has {{Fraction|3|1|2}} times the mass of the next asteroid, [[4 Vesta|Vesta]], but it has only {{Fraction|78}} the mass of the [[Moon]], and its surface gravity is {{Fraction|35}} that of Earth ({{Fraction|6}} of the Moon's). It is close to being in [[hydrostatic equilibrium]], but some deviations from an equilibrium shape have yet to be explained.<ref name="EPSC">{{Cite book |last1=Raymond |first1=C. |title=European Planetary Science Congress |last2=Castillo-Rogez |first2=J. C. |last3=Park |first3=R. S. |last4=Ermakov |first4=A. |last5=Bland |first5=M. T. |last6=Marchi |first6=S. |last7=Prettyman |first7=T. |last8=Ammannito |first8=E. |last9=De Sanctis |first9=M. C. |date=September 2018 |volume=12 |chapter=Dawn Data Reveal Ceres' Complex Crustal Evolution |display-authors=4 |access-date=19 July 2020 |chapter-url=https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-645-1.pdf |archive-url=https://web.archive.org/web/20200130111631/https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-645-1.pdf |archive-date=30 January 2020 |url-status=live |author10=Russell, C.T.}}</ref> [[Mathematical model|Modelling]] has suggested Ceres's rocky material is partially [[Planetary differentiation|differentiated]], and that it may possess a small [[planetary core|core]],<ref name="Neumann2015">{{Cite journal |last1=Neumann |first1=W. |last2=Breuer |first2=D. |last3=Spohn |first3=T. |date=2 December 2015 |title=Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation |url=http://www.aanda.org/articles/aa/pdf/2015/12/aa27083-15.pdf |url-status=live |journal=Astronomy & Astrophysics |volume=584 |pages=A117 |bibcode=2015A&A...584A.117N |doi=10.1051/0004-6361/201527083 |archive-url=https://web.archive.org/web/20160822053141/http://www.aanda.org/articles/aa/pdf/2015/12/aa27083-15.pdf |archive-date=22 August 2016 |access-date=10 July 2016 |doi-access=free}}</ref><ref name="Bhatia2017">{{Cite journal |last1=Bhatia |first1=G.K. |last2=Sahijpal |first2=S. |year=2017 |title=Thermal evolution of trans-Neptunian objects, icy satellites, and minor icy planets in the early solar system |journal=Meteoritics & Planetary Science |volume=52 |issue=12 |pages=2470–2490 |bibcode=2017M&PS...52.2470B |doi=10.1111/maps.12952 |s2cid=133957919|doi-access=free }}</ref> but the data is also consistent with a [[Mantle (geology)|mantle]] of hydrated [[silicate]]s and no core.<ref name="EPSC" /> Because ''Dawn'' lacked a [[magnetometer]], it is not known if Ceres has a [[magnetic field]]; it is believed not to.<ref>{{cite web|title=The Solar Wind Interaction with Vesta and Ceres: Implications for their Magnetic Moments|last1=Russell|first1=C.T.|last2=Villarreal|first2=M.N.|last3=Prettyman|first3=T.H.|last4=Yamashita|first4=N.|url=https://www.cosmos.esa.int/documents/1700208/1718754/16_Russell_Solar+Wind+Interaction+with+Vesta+and+Ceres.pdf/dffe9040-3e32-5d4d-8322-a3837c69cd47|publisher=ESA Cosmos|date=16 May 2018|access-date=10 October 2022}}</ref><ref>{{Cite journal |last1=Nordheim |first1=T.A. |last2=Castillo-Rogez |first2=J.C. |last3=Villarreal |first3=M.N. |last4=Scully |first4=J.E.C. |last5=Costello |first5=E.S. |date=May 2022 |title=The Radiation Environment of Ceres and Implications for Surface Sampling |journal=Astrobiology |language=en |volume=22 |issue=5 |pages=509–519 |doi=10.1089/ast.2021.0080 |pmid=35447049 |bibcode=2022AsBio..22..509N }}</ref> Ceres's internal differentiation may be related to its lack of a [[natural satellite]], as satellites of main belt asteroids are mostly believed to form from collisional disruption, creating an undifferentiated, [[rubble pile]] structure.<ref>{{cite journal |title=Dawn mission's search for satellites of Ceres: Intact protoplanets don't have satellites|journal=Icarus|volume=316|date=December 2018|pages=191–204|author1-first=Lucy A.|author1-last=McFadden |author2-first=David R. |author2-last=Skillman |author3-first=N. |author3-last=Memarsadeghi |doi=10.1016/j.icarus.2018.02.017 |bibcode=2018Icar..316..191M }}</ref>

=== Surface ===
==== Composition ====
The surface composition of Ceres is homogeneous on a global scale, and it is rich in [[carbonate]]s and ammoniated [[phyllosilicate]]s that have been altered by water,<ref name="EPSC" /> though water ice in the [[regolith]] varies from approximately 10% in polar latitudes to much drier, even ice-free, in the equatorial regions.<ref name="EPSC" />

Studies using the [[Hubble Space Telescope]] show [[graphite]], [[sulfur]], and [[sulfur dioxide]] on Ceres's surface. The graphite is evidently the result of [[space weathering]] on Ceres's older surfaces; the latter two are [[Volatile (astrogeology)|volatile]] under Cererian conditions and would be expected to either escape quickly or settle in cold traps, and so are evidently associated with relatively recent geological activity.<ref>{{Cite web |date=3 September 2016 |title=Sulfur, Sulfur Dioxide, Graphitized Carbon Observed on Ceres |url=http://spaceref.com/ceres/sulfur-sulfur-dioxide-graphitized-carbon-observed-on-ceres.html |access-date=8 September 2016 |publisher=spaceref.com |archive-date=29 September 2021 |archive-url=https://web.archive.org/web/20210929081230/http://spaceref.com/ceres/sulfur-sulfur-dioxide-graphitized-carbon-observed-on-ceres.html }}</ref>

[[Organic compound]]s were detected in the Ernutet crater,<ref>{{cite journal|title=New Constraints on the Abundance and Composition of Organic Matter on Ceres|last1=Kaplan|first1=Hannah H.|last2=Milliken|first2=Ralph E.|last3=Alexander|first3=Conel M. O'D.|journal=Geophysical Research Letters|volume=45|issue=11|pages=5274–5282|doi=10.1029/2018GL077913|date=21 May 2018|bibcode= 2018GeoRL..45.5274K|s2cid= 51801398|doi-access=free}}</ref> and at least another eleven regions are candidates for their presence.<ref>{{cite journal |last1=Rizos |first1=J. L. |last2=Sunshine |first2=J. M. |last3=Daly |first3=R. T. |last4=Nathues |first4=A. |last5=De Sanctis |first5=C. |last6=Raponi |first6=A. |last7=Pasckert |first7=J. H. |last8=Farnham |first8=T. L. |last9=Kloos |first9=J. |last10=Ortiz |first10=J. L. |title=New Candidates for Organic-rich Regions on Ceres |journal=The Planetary Science Journal |year=2024 |volume=5 |issue=12 |page=262 |doi=10.3847/PSJ/ad86ba |doi-access=free |arxiv=2406.14893 |bibcode=2024PSJ.....5..262R }}</ref> Most of the planet's near surface is rich in carbon, at approximately 20% by mass.<ref name="Nature 12 2018">{{Cite journal |last1=Marchi |first1=S. |last2=Raponi |first2=A. |last3=Prettyman |first3=T. H. |last4=De Sanctis |first4=M. C. |last5=Castillo-Rogez |first5=J. |last6=Raymond |first6=C. A. |last7=Ammannito |first7=E. |last8=Bowling |first8=T. |last9=Ciarniello |first9=M. |last10=Kaplan |first10=H. |last11=Palomba |first11=E. |year=2018 |title=An aqueously altered carbon-rich Ceres |journal=[[Nature Astronomy]] |volume=3 |issue=2 |pages=140–145 |doi=10.1038/s41550-018-0656-0 |last12=Russell |first12=C. T. |last13=Vinogradoff |first13=V. |last14=Yamashita |first14=N. |s2cid=135013590}}</ref> The carbon content is more than five times higher than in carbonaceous chondrite meteorites analysed on Earth.<ref name="Nature 12 2018" /> The surface carbon shows evidence of being mixed with products of rock-water interactions, such as clays.<ref name="Nature 12 2018" /> This chemistry suggests Ceres formed in a cold environment, perhaps outside the orbit of Jupiter, and that it accreted from ultra-carbon-rich materials in the presence of water, which could provide conditions favourable to organic chemistry.<ref name="Nature 12 2018" />
<gallery mode="packed">
File:PIA21755-CeresMap-CraterNames-20170901.jpg|Black-and-white photographic map of Ceres, centred on 180° longitude, with official nomenclature (September 2017)
File:PIA20126-Ceres-PolarRegions-Dawn-20151023.jpg|Ceres, polar regions (November 2015): North (left); south (right). The south pole is in shadow. "Ysolo Mons" has since been renamed "Yamor Mons."<ref name="ysolo">{{Cite web |date=7 December 2016 |title=Name Changed on Ceres |url=https://astrogeology.usgs.gov/news/nomenclature/name-changed-on-ceres |url-status=live |archive-url=https://web.archive.org/web/20210819131632/https://astrogeology.usgs.gov/news/nomenclature/name-changed-on-ceres |archive-date=19 August 2021 |access-date=2021-08-19 |publisher=USGS}}</ref>
</gallery>

==== Craters ====
[[File:PIA20918-Ceres-Dawn-GlobalMap-Annotated-20160926.jpg|thumb|upright=3|Topographic map of Ceres. The lowest crater floors (indigo) and the highest peaks (white) represent a difference of 15&nbsp;km (10&nbsp;mi) elevation.<ref name="NASA-20150728-el">{{Cite web |last=Landau |first=Elizabeth |date=28 July 2015 |title=New Names and Insights at Ceres |url=http://www.jpl.nasa.gov/news/news.php?feature=4669 |url-status=live |archive-url=https://web.archive.org/web/20160106220022/http://www.jpl.nasa.gov/news/news.php?feature=4669 |archive-date=6 January 2016 |access-date=28 July 2015 |website=NASA}}</ref> "Ysolo Mons" has been renamed "Yamor Mons."<ref name="ysolo" />|center]]''Dawn'' revealed that Ceres has a heavily cratered surface, though with fewer large craters than expected.<ref name="marchi" /> Models based on the formation of the current asteroid belt had predicted Ceres should have ten to fifteen craters larger than {{convert|400|km|mi|abbr=on}} in diameter.<ref name="marchi">{{Cite journal |last1=Marchi |first1=S. |last2=Ermakov |first2=A. I. |last3=Raymond |first3=C. A. |last4=Fu |first4=R. R. |last5=O'Brien |first5=D. P. |last6=Bland |first6=M. T. |last7=Ammannito |first7=E. |last8=De Sanctis |first8=M. C. |last9=Bowling |first9=T. |last10=Schenk |first10=P. |last11=Scully |first11=J. E. C. |date=26 July 2016 |title=The missing large impact craters on Ceres |journal=[[Nature Communications]] |volume=7 |article-number=12257 |bibcode=2016NatCo...712257M |doi=10.1038/ncomms12257  |doi-access=free|pmc=4963536 |pmid=27459197 |last12=Buczkowski |first12=D. L. |last13=Williams |first13=D. A. |last14=Hiesinger |first14=H. |last15=Russell |first15=C. T.}}</ref> The largest confirmed crater on Ceres, [[Kerwan (crater)|Kerwan Basin]], is {{convert|284|km|mi|abbr=on}} across.<ref name="kerwan" /> The most likely reason for this is [[Viscoelasticity|viscous relaxation]] of the crust slowly flattening out larger impacts.<ref name="marchi" /><ref>{{Cite journal |last1=Nathues |first1=A. |last2=Platz |first2=T. |last3=Thangjam |first3=G. |last4=Hoffmann |first4=M. |last5=Scully |first5=J.E.C. |last6=Stein |first6=N. |last7=Ruesch |first7=O. |last8=Mengel |first8=K. |date=2019 |title=Occator crater in color at highest spatial resolution |url= |journal=Icarus |volume=320 |pages=24–38 |doi=10.1016/j.icarus.2017.12.021 |bibcode=2019Icar..320...24N }}</ref>

Ceres's north polar region shows far more cratering than the equatorial region, with the eastern equatorial region in particular comparatively lightly cratered.<ref name="strom" /> The overall size frequency of craters of between twenty and a hundred kilometres (10–60&nbsp;mi) is consistent with their having originated in the [[Late Heavy Bombardment]], with craters outside the ancient polar regions likely erased by early [[cryovolcanism]].<ref name="strom">{{Cite journal |last1=Strom |first1=R.G. |last2=Marchi |first2=S. |last3=Malhotra |first3=R. |year=2018 |title=Ceres and the Terrestrial Planets Impact Cratering Record |journal=Icarus |volume=302 |pages=104–108 |arxiv=1804.01229 |bibcode=2018Icar..302..104S |doi=10.1016/j.icarus.2017.11.013 |s2cid=119009942}}</ref> Three large shallow basins (planitiae) with degraded rims are likely to be eroded craters.<ref name="EPSC" /> The largest, [[Vendimia Planitia]], at {{convert|800|km|mi|abbr=on}} across,<ref name="marchi" /> is also the largest single geographical feature on Ceres.<ref>{{Cite web |date=23 March 2018 |title=Hanami Planum on Ceres |url=https://www.nasa.gov/image-feature/jpl/pia21921/hanami-planum-on-ceres |url-status=live |archive-url=https://web.archive.org/web/20210929081231/https://www.nasa.gov/image-feature/jpl/pia21921/hanami-planum-on-ceres/ |archive-date=29 September 2021 |access-date=17 August 2021 |publisher=NASA}}</ref> Two of the three have higher than average ammonium concentrations.<ref name="EPSC" />

''Dawn'' observed 4,423 boulders larger than {{convert|105|m|abbr=on}} in diameter on the surface of Ceres. These boulders likely formed through impacts, and are found within or near craters, though not all craters contain boulders. Large boulders are more numerous at higher latitudes. Boulders on Ceres are brittle and degrade rapidly due to thermal stress (at dawn and dusk, the surface temperature changes rapidly) and meteoritic impacts. Their maximum age is estimated to be 150&nbsp;million years, much shorter than the lifetime of boulders on Vesta.<ref>{{Cite journal |last1=Schröder |first1=Stefan E |last2=Carsenty |first2=Uri |last3=Hauber |first3=Ernst |last4=Raymond |first4=Carol |last5=Russell |first5=Christopher |date=May 2021 |title=The brittle boulders of dwarf planet Ceres |journal=Planetary Science Journal |volume=2 |issue=3 |page=111 |arxiv=2105.11841 |bibcode=2021PSJ.....2..111S |doi=10.3847/PSJ/abfe66 |s2cid=235187212 |doi-access=free }}</ref>

==== Tectonic features ====
Although Ceres lacks [[plate tectonics]],<ref>{{Cite journal |last1=Stern |first1=Robert J. |last2=Gerya |first2=Taras |last3=Tackley |first3=Paul J. |date=January 2018 |title=Stagnant lid tectonics: Perspectives from silicate planets, dwarf planets, large moons, and large asteroids |journal=Geoscience Frontiers |language=en |volume=9 |issue=1 |pages=103–119 |doi=10.1016/j.gsf.2017.06.004 |bibcode=2018GeoFr...9..103S |doi-access=free |hdl=20.500.11850/224778 |hdl-access=free }}</ref> with the vast majority of its surface features linked either to impacts or to cryovolcanic activity,<ref name="Sori" /> several potentially [[tectonic]] features have been tentatively identified on its surface, particularly in its eastern hemisphere. The Samhain Catenae, kilometre-scale linear fractures on Ceres's surface, lack any apparent link to impacts and bear a stronger resemblance to pit [[crater chain]]s, which are indicative of buried [[normal fault]]s. Also, several craters on Ceres have shallow, fractured floors consistent with cryomagmatic intrusion.<ref>{{cite conference |last1=Buczkowski |first1=D. |last2=Scully |first2=J. E. C. |last3=Raymond |first3=C. A. |last4=Russell |first4=C. T. |date=December 2017 |title=Exploring Tectonic Activity on Vesta and Ceres |conference=American Geophysical Union, Fall Meeting 2017, Abstract #P53G-02 |volume=2017 |bibcode=2017AGUFM.P53G..02B }}</ref>

==== Cryovolcanism ====
{{Main|Bright spots on Ceres}}
{{multiple image
| direction         = vertical
| align             = right
| header_align      = center
| caption_align     = center
| width             = 210
| image2            = PIA21913-DwarfPlanetCeres-OccatorCrater-SimulatedPerspective-20171212.jpg
| alt2              = Icy patches against a grey, flat background
| caption2          = Simulated view of Cerealia and Vinalia Faculae
| image1            = Lone conical mountain on Ceres from HAMO.jpg
| alt1              = A smooth-sided mountain rising from a grey surface
| caption1          = [[Ahuna Mons]] (center) is an estimated {{convert|5|km|mi|0|abbr=on}} high on its steepest side.<ref name="PIA20348">{{Cite web |date=7 March 2016 |title=PIA20348: Ahuna Mons Seen from LAMO |url=http://photojournal.jpl.nasa.gov/catalog/PIA20348 |url-status=live |archive-url=https://web.archive.org/web/20160311021119/http://photojournal.jpl.nasa.gov/catalog/PIA20348 |archive-date=11 March 2016 |access-date=14 April 2016 |publisher=[[Jet Propulsion Laboratory]]}}</ref>
}}

Ceres has one prominent mountain, [[Ahuna Mons]]; this appears to be a cryovolcano and has few craters, suggesting a maximum age of 240&nbsp;million years.<ref name="sori2" /> Its relatively high gravitational field suggests it is dense, and thus composed more of rock than ice, and that its placement is likely due to [[diapir]]ism of a slurry of brine and silicate particles from the top of the mantle.<ref name="liebert" /> It is roughly antipodal to Kerwan Basin. Seismic energy from the Kerwan-forming impact may have focused on the opposite side of Ceres, fracturing the outer layers of the crust and triggering the movement of high-viscosity cryomagma (muddy water ice softened by its content of salts) onto the surface.<ref name="Ruesch2016">{{Cite journal |last1=Ruesch |first1=O. |last2=Platz |first2=T. |last3=Schenk |first3=P. |last4=McFadden |first4=L. A. |last5=Castillo-Rogez |first5=J. C. |last6=Quick |first6=L. C. |last7=Byrne |first7=S. |last8=Preusker |first8=F. |last9=OBrien |first9=D. P. |last10=Schmedemann |first10=N. |last11=Williams |first11=D. A. |date=2 September 2016 |title=Cryovolcanism on Ceres |journal=Science |volume=353 |issue=6303 |article-number=aaf4286 |bibcode=2016Sci...353.4286R |doi=10.1126/science.aaf4286 |pmid=27701087 |doi-access=free |last12=Li |first12=J.- Y. |last13=Bland |first13=M. T. |last14=Hiesinger |first14=H. |last15=Kneissl |first15=T. |last16=Neesemann |first16=A. |last17=Schaefer |first17=M. |last18=Pasckert |first18=J. H. |last19=Schmidt |first19=B. E. |last20=Buczkowski |first20=D. L. |last21=Sykes |first21=M. V. |last22=Nathues |first22=A. |last23=Roatsch |first23=T. |last24=Hoffmann |first24=M. |last25=Raymond |first25=C. A. |last26=Russell |first26=C. T.}}</ref> Kerwan too shows evidence of the effects of liquid water due to impact-melting of subsurface ice.<ref name="kerwan">{{Cite journal |last1=Williams |first1=David A. |last2=Kneiss |first2=T. |date=December 2018 |title=The geology of the Kerwan quadrangle of dwarf planet Ceres: Investigating Ceres' oldest, largest impact basin |journal=Icarus |volume=316 |pages=99–113 |bibcode=2018Icar..316...99W |doi=10.1016/j.icarus.2017.08.015 }}</ref>

A 2018 [[computer simulation]] suggests that cryovolcanoes on Ceres, once formed, recede due to viscous relaxation over several hundred million years. The team identified 22 features as strong candidates for relaxed cryovolcanoes on Ceres's surface.<ref name="sori2">{{Cite journal |first1=Michael T. |last1=Sori |first2=Hanna G. |last2=Sizemore |display-authors=etal |date=December 2018 |title=Cryovolcanic rates on Ceres revealed by topography |journal=Nature Astronomy |volume=2 |issue=12 |pages=946–950 |bibcode=2018NatAs...2..946S |doi=10.1038/s41550-018-0574-1 }}</ref><ref name="vanishing">{{Cite journal |last1=Sori |first1=Michael M. |last2=Byrne |first2=Shane |last3=Bland |first3=Michael T. |last4=Bramson |first4=Ali M. |last5=Ermakov |first5=Anton I. |last6=Hamilton |first6=Christopher W. |last7=Otto |first7=Katharina A. |last8=Ruesch |first8=Ottaviano |last9=Russell |first9=Christopher T. |year=2017 |title=The vanishing cryovolcanoes of Ceres |url=https://repository.arizona.edu/bitstream/10150/623032/1/Sori_et_al-2017-Geophysical_Research_Letters.pdf |url-status=live |journal=[[Geophysical Research Letters]] |volume=44 |issue=3 |pages=1243–1250 |bibcode=2017GeoRL..44.1243S |doi=10.1002/2016GL072319 |archive-url=https://web.archive.org/web/20210929081236/https://repository.arizona.edu/bitstream/handle/10150/623032/Sori_et_al-2017-Geophysical_Research_Letters.pdf;jsessionid=36FE8987BD3FBEC127C6BCE092D3B831?sequence=1 |archive-date=29 September 2021 |access-date=25 August 2019 |hdl-access=free |hdl=10150/623032 |s2cid=52832191}}</ref> [[Yamor Mons]], an ancient, impact-cratered peak, resembles Ahuna Mons despite being much older, due to it lying in Ceres's northern polar region, where lower temperatures prevent viscous relaxation of the crust.<ref name="Sori" /> Models suggest that, over the past billion years, one cryovolcano has formed on Ceres on average every fifty million years.<ref name="Sori">{{Cite web |date=17 September 2018 |title=Ceres takes life an ice volcano at a time |url=https://phys.org/news/2018-09-ceres-life-ice-volcano.html |url-status=live |archive-url=https://web.archive.org/web/20201109040853/https://phys.org/news/2018-09-ceres-life-ice-volcano.html |archive-date=9 November 2020 |access-date=22 April 2019 |publisher=University of Arizona |language=en-us}}</ref> The eruptions may be linked to ancient impact basins but are not uniformly distributed over Ceres.<ref name="Sori" /> The model suggests that, contrary to findings at Ahuna Mons, Cererian cryovolcanoes must be composed of far less dense material than average for Ceres's crust, or the observed viscous relaxation could not occur.<ref name="sori2" />

An unexpectedly large number of Cererian craters have central pits, perhaps due to cryovolcanic processes; others have central peaks.<ref>{{Cite web |title=News – Ceres Spots Continue to Mystify in Latest Dawn Images |url=https://solarsystem.nasa.gov/news/602/ceres-spots-continue-to-mystify-in-latest-dawn-images/ |url-status=live |archive-url=https://web.archive.org/web/20210725110508/https://solarsystem.nasa.gov/news/602/ceres-spots-continue-to-mystify-in-latest-dawn-images/ |archive-date=25 July 2021 |access-date=25 July 2021 |website=NASA/JPL}}</ref> Hundreds of [[Bright spots on Ceres|bright spots]] (faculae) have been observed by ''Dawn'', the brightest in the middle of {{convert|80|km|mi|abbr=on}} [[Occator Crater]].<ref>{{Cite web |title=USGS: Ceres nomenclature |url=https://planetarynames.wr.usgs.gov/images/ceres.pdf |url-status=live |archive-url=https://web.archive.org/web/20151115202652/http://planetarynames.wr.usgs.gov/images/ceres.pdf |archive-date=15 November 2015 |access-date=16 July 2015}}</ref> The bright spot in the centre of Occator is named [[Cerealia]] Facula,<ref name="CF">{{GPN|15530|Cerealia Facula}}</ref> and the group of bright spots to its east, [[Vinalia]] Faculae.<ref name="VF">{{GPN|15531|Vinalia Faculae}}</ref> Occator possesses a pit 9–10&nbsp;km wide, partially filled by a central dome. The dome post-dates the faculae and is likely due to freezing of a subterranean reservoir, comparable to [[pingo]]s in Earth's Arctic region.<ref name="NASA-20180724">{{Cite web |last1=Landau |first1=Elizabeth |last2=McCartney |first2=Gretchen |date=24 July 2018 |title=What Looks Like Ceres on Earth? |url=https://www.nasa.gov/feature/jpl/what-looks-like-ceres-on-earth |url-status=live |archive-url=https://web.archive.org/web/20210531021809/https://www.nasa.gov/feature/jpl/what-looks-like-ceres-on-earth/ |archive-date=31 May 2021 |access-date=26 July 2021 |website=NASA}}</ref><ref>{{Cite journal |last1=Schenk |first1=Paul |last2=Sizemore |first2=Hanna |display-authors=etal |date=1 March 2019 |title=The central pit and dome at Cerealia Facula bright deposit and floor deposits in Occator Crater, Ceres: Morphology, comparisons and formation |journal=Icarus |volume=320 |pages=159–187 |bibcode=2019Icar..320..159S |doi=10.1016/j.icarus.2018.08.010 |s2cid=125527752}}</ref> A haze periodically appears above Cerealia, supporting the hypothesis that some sort of outgassing or sublimating ice formed the bright spots.<ref>{{Cite web |last=Rivkin |first=Andrew |date=21 July 2015 |title=Dawn at Ceres: A haze in Occator Crater? |url=http://www.planetary.org/blogs/guest-blogs/2015/0721-dawn-at-ceres-a-haze-in-occator-rivkin.html |url-status=live |archive-url=https://web.archive.org/web/20160514052923/http://www.planetary.org/blogs/guest-blogs/2015/0721-dawn-at-ceres-a-haze-in-occator-rivkin.html |archive-date=14 May 2016 |access-date=8 March 2017 |publisher=The Planetary Society}}</ref> In March 2016 ''Dawn'' found definitive evidence of water ice on the surface of Ceres at [[Oxo crater]].<ref>{{Cite web |last=Redd |first=Nola Taylor |title=Water Ice on Ceres Boosts Hopes for Buried Ocean [Video] |url=http://www.scientificamerican.com/article/water-ice-on-ceres-boosts-hopes-for-buried-ocean-video/ |url-status=live |archive-url=https://web.archive.org/web/20160407113800/http://www.scientificamerican.com/article/water-ice-on-ceres-boosts-hopes-for-buried-ocean-video/ |archive-date=7 April 2016 |access-date=7 April 2016 |website=Scientific American}}</ref>

On 9 December 2015, NASA scientists reported that the bright spots on Ceres may be due to a type of salt from evaporated brine containing [[magnesium sulfate]] hexahydrate (MgSO<sub>4</sub>·6H<sub>2</sub>O); the spots were also found to be associated with ammonia-rich clays.<ref name="NASA-20151209-el" /> [[Near-infrared]] spectra of these bright areas were reported in 2017 to be consistent with a large amount of [[sodium carbonate]] ({{chem|Na|2|CO|3}}) and smaller amounts of [[ammonium chloride]] ({{chem|N|H|4|Cl}}) or [[ammonium bicarbonate]] ({{chem|N|H|4|H|C|O|3}}).<ref>{{Cite journal |last1=Vu |first1=Tuan H. |last2=Hodyss |first2=Robert |last3=Johnson |first3=Paul V. |last4=Choukroun |first4=Mathieu |date=July 2017 |title=Preferential formation of sodium salts from frozen sodium-ammonium-chloride-carbonate brines – Implications for Ceres' bright spots |journal=Planetary and Space Science |volume=141 |pages=73–77 |bibcode=2017P&SS..141...73V |doi=10.1016/j.pss.2017.04.014}}</ref><ref>{{Cite journal |last1=McCord |first1=Thomas B. |last2=Zambon |first2=Francesca |year=2019 |title=The surface composition of Ceres from the Dawn mission |journal=Icarus |volume=318 |pages=2–13 |bibcode=2019Icar..318....2M |doi=10.1016/j.icarus.2018.03.004 |s2cid=125115208}}</ref> These materials have been suggested to originate from the crystallisation of brines that reached the surface.<ref>{{Cite journal |last1=Quick |first1=Lynnae C. |last2=Buczkowski |first2=Debra L. |last3=Ruesch |first3=Ottaviano |last4=Scully |first4=Jennifer E. C. |last5=Castillo-Rogez |first5=Julie |last6=Raymond |first6=Carol A. |last7=Schenk |first7=Paul M. |last8=Sizemore |first8=Hanna G. |last9=Sykes |first9=Mark V. |date=1 March 2019 |title=A Possible Brine Reservoir Beneath Occator Crater: Thermal and Compositional Evolution and Formation of the Cerealia Dome and Vinalia Faculae |journal=Icarus |volume=320 |pages=119–135 |bibcode=2019Icar..320..119Q |doi=10.1016/j.icarus.2018.07.016 }}</ref> In August 2020 NASA confirmed that Ceres was a water-rich body with a deep reservoir of brine that percolated to the surface in hundreds of locations<ref>{{Cite journal |last1=Stein |first1=N. T. |last2=Ehlmann |first2=B. L. |date=1 March 2019 |title=The formation and evolution of bright spots on Ceres |journal=Icarus |volume=320 |pages=188–201 |bibcode=2019Icar..320..188S |doi=10.1016/j.icarus.2017.10.014 |doi-access=free}}</ref> causing "bright spots", including those in Occator Crater.<ref name="PHY-20200811">{{Cite news |last=McCartney |first=Gretchen |date=11 August 2020 |title=Mystery solved: Bright areas on Ceres come from salty water below |work=[[Phys.org]] |url=https://phys.org/news/2020-08-mystery-bright-areas-ceres-salty.html |url-status=live |access-date=12 August 2020 |archive-url=https://web.archive.org/web/20200811150523/https://phys.org/news/2020-08-mystery-bright-areas-ceres-salty.html |archive-date=11 August 2020}}</ref>

=== Internal structure ===
[[File:PIA22660-Ceres-DwarfPlanet-Inside-ArtistConcept-20180814.jpg|thumb|left|alt=a cutaway image of the interior of Ceres|Three-layer model of Ceres's internal structure:
{{Bulleted list|item_style=margin-bottom: 0|Thick outer crust (ice, salts, hydrated minerals)|Salt-rich liquid (''brine'') and rock|"Mantle" (hydrated rock)}}]]The active geology of Ceres is driven by ice and brines. Water leached from rock is estimated to possess a [[salinity]] of around 5%. Altogether, Ceres is approximately 50% water by volume (compared to 0.1% for Earth) and 73% rock by mass.<ref name="Dawn2017">{{Cite web |last1=Rogez |first1=J. C. Castillo |last2=Raymond |first2=C. A. |last3=Russell |first3=C. T. |last4=Team |first4=Dawn |year=2017 |title=''Dawn'' at Ceres: What Have We Learned? |url=http://sites.nationalacademies.org/cs/groups/ssbsite/documents/webpage/ssb_183286.pdf |url-status=live |archive-url=https://web.archive.org/web/20181008123813/http://sites.nationalacademies.org/cs/groups/ssbsite/documents/webpage/ssb_183286.pdf |archive-date=8 October 2018 |access-date=19 July 2021 |website=NASA, JPL}}</ref>

Ceres's largest craters are several kilometres deep, inconsistent with an ice-rich shallow subsurface. The fact that the surface has preserved craters almost {{convert|300|km|-2|abbr=on}} in diameter indicates that the outermost layer of Ceres is roughly 1000 times stronger than water ice. This is consistent with a mixture of [[silicate]]s, hydrated salts and [[methane clathrate]]s, with no more than 30% water ice by volume.<ref name="EPSC" /><ref>{{Cite journal |first1=Michael T. |last1=Bland |first2=Carol A. |last2=Raymond |display-authors=etal |year=2016 |title=Composition and structure of the shallow subsurface of Ceres revealed by crater morphology |url=https://www.nature.com/articles/ngeo2743 |url-status=live |journal=Nature Geoscience |volume=9 |issue=7 |pages=538–542 |bibcode=2016NatGe...9..538B |doi=10.1038/ngeo2743 |archive-url=https://web.archive.org/web/20210915144834/https://www.nature.com/articles/ngeo2743 |archive-date=15 September 2021 |access-date=15 September 2021 |hdl=10919/103024|hdl-access=free }}</ref>

Gravity measurements from ''Dawn'' have generated three competing models for Ceres's interior.<ref name="Dawn2017" /> In the three-layer model, Ceres is thought to consist of an outer, {{convert|40|km||abbr=on}} thick crust of ice, salts and hydrated minerals and an inner muddy "[[Mantle (geology)|mantle]]" of hydrated rock, such as clays, separated by a {{convert|60|km||abbr=on}} layer of a muddy mixture of brine and rock.<ref name="artist">{{Cite web |date=14 August 2018 |title=PIA22660: Ceres' Internal Structure (Artist's Concept) |url=https://photojournal.jpl.nasa.gov/catalog/PIA22660 |website=Photojournal |publisher=Jet Propulsion Laboratory |url-status=live |archive-url=https://web.archive.org/web/20190421180803/https://photojournal.jpl.nasa.gov/catalog/PIA22660 |archive-date=21 April 2019 |access-date=22 April 2019}} {{Source-attribution|inline=y}}</ref> It is not possible to tell if Ceres's deep interior contains liquid or a core of dense material rich in metal,<ref name="artist" /> but the low central density suggests it may retain about 10% [[porosity]].<ref name="Dawn2017" /> One study estimated the densities of the core and mantle/crust to be 2.46–2.90 and 1.68–1.95&nbsp;g/cm<sup>3</sup> respectively, with the mantle and crust together being {{convert|70|-|190|km|-1|abbr=on}} thick. Only partial dehydration (expulsion of ice) from the core is expected, though the high density of the mantle relative to water ice reflects its enrichment in silicates and salts.<ref name="Park2016">{{Cite journal |last1=Park |first1=R. S. |last2=Konopliv |first2=A. S. |last3=Bills |first3=B. G. |last4=Rambaux |first4=N. |last5=Castillo-Rogez |first5=J. C. |last6=Raymond |first6=C. A. |last7=Vaughan |first7=A. T. |last8=Ermakov |first8=A. I. |last9=Zuber |first9=M. T. |last10=Fu |first10=R. R. |last11=Toplis |first11=M. J. |date=3 August 2016 |title=A partially differentiated interior for (1) Ceres deduced from its gravity field and shape |journal=Nature |volume=537 |issue=7621 |pages=515–517 |bibcode=2016Natur.537..515P |doi=10.1038/nature18955 |pmid=27487219 |last12=Russell |first12=C. T. |last13=Nathues |first13=A. |last14=Preusker |first14=F. |s2cid=4459985|url=https://resolver.sub.uni-goettingen.de/purl?gro-2/86708 }}</ref> That is, the core (if it exists), the mantle and crust all consist of rock and ice, though in different ratios.

Ceres's mineral composition can be determined (indirectly) only for its outer {{convert|100|km|-1|abbr=on}}. The solid outer crust, {{convert|40|km||abbr=on}} thick, is a mixture of ice, salts, and hydrated minerals. Under that is a layer that may contain a small amount of brine. This extends to a depth of at least the {{convert|100|km|-1|adj=on|abbr=on}} limit of detection. Under that is thought to be a mantle dominated by hydrated rocks such as clays.<ref name="artist" />

In one two-layer model, Ceres consists of a core of [[chondrule]]s and a mantle of mixed ice and micron-sized solid particulates ("mud"). Sublimation of ice at the surface would leave a deposit of hydrated particulates perhaps twenty metres thick. The range of the extent of differentiation is consistent with the data, from a large, {{convert|360|km||abbr=on}} core of 75% chondrules and 25% particulates and a mantle of 75% ice and 25% particulates, to a small, {{convert|85|km||round=5|abbr=on}} core consisting nearly entirely of particulates and a mantle of 30% ice and 70% particulates. With a large core, the core–mantle boundary should be warm enough for pockets of brine. With a small core, the mantle should remain liquid below {{convert|110|km|abbr=on}}. In the latter case a 2% freezing of the liquid reservoir would compress the liquid enough to force some to the surface, producing cryovolcanism.<ref>{{cite journal|last1=Neveu|first1=M.|last2=Desch|first2=S. J.|title=Geochemistry, thermal evolution, and cryovolcanism on Ceres with a muddy ice mantle |journal=Geophysical Research Letters |year=2016 |volume=42 |issue=23 |doi=10.1002/2015GL066375 |s2cid=51756619 |doi-access=free}}</ref>

A second two-layer model suggests a partial differentiation of Ceres into a volatile-rich crust and a denser mantle of hydrated silicates. A range of densities for the crust and mantle can be calculated from the types of meteorite thought to have impacted Ceres. With CI-class meteorites (density 2.46 g/cm<sup>3</sup>), the crust would be approximately {{convert|70|km|-1|abbr=on}} thick and have a density of 1.68 g/cm<sup>3</sup>; with CM-class meteorites (density 2.9 g/cm<sup>3</sup>), the crust would be approximately {{convert|190|km|abbr=on}} thick and have a density of 1.9 g/cm<sup>3</sup>. Best-fit modelling yields a crust approximately {{convert|40|km|abbr=on}} thick with a density of approximately 1.25 g/cm<sup>3</sup>, and a mantle/core density of approximately 2.4 g/cm<sup>3</sup>.<ref name="EPSC" />

== Exosphere ==
In 2017, ''Dawn'' confirmed that Ceres has a transient atmosphere of water vapour.<ref>{{Cite news |date=6 April 2017 |title=Confirmed: Ceres Has a Transient Atmosphere |language=en |work=Universe Today |url=https://www.universetoday.com/134922/confirmed-ceres-transient-atmosphere/ |url-status=live |access-date=14 April 2017 |archive-url=https://web.archive.org/web/20170415103956/https://www.universetoday.com/134922/confirmed-ceres-transient-atmosphere/ |archive-date=15 April 2017}}</ref> Hints of an atmosphere had appeared in early 2014, when the [[Herschel Space Observatory]] detected localised mid-latitude sources of water vapour on Ceres, no more than {{convert|60|km|-1|abbr=on}} in diameter, which each give off approximately {{val|e=26}} molecules (3&nbsp;kg) of water per second.<ref name="Kuppers2014">{{Cite journal |last1=Küppers |first1=M. |last2=O'Rourke |first2=L. |last3=Bockelée-Morvan |first3=D.|author3-link=Dominique Bockelée-Morvan |last4=Zakharov |first4=V. |last5=Lee |first5=S. |last6=Von Allmen |first6=P. |last7=Carry |first7=B. |last8=Teyssier |first8=D. |last9=Marston |first9=A. |last10=Müller |first10=T. |last11=Crovisier |first11=J. |date=23 January 2014 |title=Localized sources of water vapour on the dwarf planet (1) Ceres |journal=Nature |volume=505 |issue=7484 |pages=525–527 |bibcode=2014Natur.505..525K |doi=10.1038/nature12918 |pmid=24451541 |last12=Barucci |first12=M. A. |last13=Moreno |first13=R. }}</ref><ref name="Campins2014">{{Cite journal |last1=Campins |first1=H. |last2=Comfort |first2=C. M. |date=23 January 2014 |title=Solar system: Evaporating asteroid |journal=Nature |volume=505 |issue=7484 |pages=487–488 |bibcode=2014Natur.505..487C |doi=10.1038/505487a |pmid=24451536 |doi-access=free |s2cid=4396841}}</ref>{{efn | This emission rate is modest compared to those calculated for the tidally driven plumes of [[Enceladus]] (a smaller body) and [[Europa (moon)|Europa]] (a larger body), 200&nbsp;kg/s<ref name="Hansen2006">{{Cite journal |last1=Hansen |first1=C. J. |last2=Esposito |first2=L. |last3=Stewart |first3=A. I. |last4=Colwell |first4=J. |last5=Hendrix |first5=A. |last6=Pryor |first6=W. |last7=Shemansky |first7=D. |last8=West |first8=R. |date=10 March 2006 |title=Enceladus' Water Vapor Plume |journal=Science |volume=311 |issue=5766 |pages=1422–1425 |bibcode=2006Sci...311.1422H |doi=10.1126/science.1121254 |pmid=16527971 |s2cid=2954801}}</ref> and 7000&nbsp;kg/s,<ref name="Europa tidal forces 2013">{{Cite journal |last1=Roth |first1=L. |last2=Saur |first2=J. |last3=Retherford |first3=K. D. |last4=Strobel |first4=D. F. |last5=Feldman |first5=P. D. |last6=McGrath |first6=M. A. |last7=Nimmo |first7=F. |date=26 November 2013 |title=Transient Water Vapor at Europa's South Pole |url=http://spacetelescope.org/static/archives/releases/science_papers/heic1322a.pdf |url-status=live |journal=Science |volume=343 |issue=6167 |pages=171–174 |bibcode=2014Sci...343..171R |doi=10.1126/science.1247051 |pmid=24336567 |archive-url=https://web.archive.org/web/20131216014258/http://www.spacetelescope.org/static/archives/releases/science_papers/heic1322a.pdf |archive-date=16 December 2013 |access-date=26 January 2014 |s2cid=27428538}}</ref> respectively.}} Two potential source regions, designated Piazzi (123°E, 21°N) and Region A (231°E, 23°N), were visualised in the [[near infrared]] as dark areas (Region A also has a bright centre) by the [[W. M. Keck Observatory]]. Possible mechanisms for the vapour release are sublimation from approximately {{convert|0.6|km2|1|abbr=on}} of exposed surface ice, [[cryovolcanic]] eruptions resulting from [[Radioactive decay|radiogenic]] internal heat,<ref name="Kuppers2014" /> or pressurisation of a subsurface ocean due to thickening of an overlying layer of ice.<ref name="O'Brien2015">{{Cite conference |last1=O'Brien |first1=D. P. |last2=Travis |first2=B. J. |last3=Feldman |first3=W. C. |last4=Sykes |first4=M. V. |last5=Schenk |first5=P. M. |last6=Marchi |first6=S. |last7=Russell |first7=C. T. |last8=Raymond |first8=C. A. |date=March 2015 |title=The Potential for Volcanism on Ceres due to Crustal Thickening and Pressurisation of a Subsurface Ocean |url=http://www.hou.usra.edu/meetings/lpsc2015/pdf/2831.pdf |page=2831 |archive-url=https://web.archive.org/web/20161105072942/http://www.hou.usra.edu/meetings/lpsc2015/pdf/2831.pdf |archive-date=5 November 2016 |access-date=1 March 2015 |book-title=46th [[Lunar and Planetary Science Conference]] |url-status=live}}</ref> In 2015, [[David C. Jewitt]] included Ceres in his list of [[active asteroid]]s.<ref>{{Cite book |last1=Jewitt |first1=David |chapter-url=http://www2.ess.ucla.edu/~jewitt/papers/2015/JHA15.pdf |chapter=The Active Asteroids |last2=Hsieh |first2=Henry |last3=Agarwal |first3=Jessica |title=Asteroids IV |publisher=[[University of Arizona]] |year=2015 |isbn=978-0-8165-3213-1 |editor-last=Michel |editor-first=P. |pages=221–241 |bibcode=2015aste.book..221J |doi=10.2458/azu_uapress_9780816532131-ch012 |access-date=30 January 2020 |editor-last2=others |display-editors=1 |archive-url=https://web.archive.org/web/20210830232616/http://www2.ess.ucla.edu/~jewitt/papers/2015/JHA15.pdf |archive-date=30 August 2021 |url-status=live |arxiv=1502.02361 |s2cid=119209764}}</ref> Surface water ice is unstable at distances less than 5 AU from the Sun,<ref name="Jewitt2007">{{Cite book |last1=Jewitt, D |title=Protostars and Planets V |last2=Chizmadia, L. |last3=Grimm, R. |last4=Prialnik, D |publisher=University of Arizona Press |year=2007 |isbn=978-0-8165-2654-3 |editor-last=Reipurth, B. |pages=863–878 |chapter=Water in the Small Bodies of the Solar System |access-date=11 October 2012 |editor-last2=Jewitt, D. |editor-last3=Keil, K. |chapter-url=http://www.ifa.hawaii.edu/~meech/a740/2006/spring/papers/PPV2006.pdf |archive-url=https://web.archive.org/web/20170810141735/http://www.ifa.hawaii.edu/~meech/a740/2006/spring/papers/PPV2006.pdf |archive-date=10 August 2017 |url-status=live}}</ref> so it is expected to sublime if exposed directly to solar radiation. Proton emission from solar flares and [[Coronal mass ejection|CMEs]] can sputter exposed ice patches on the surface, leading to a positive correlation between detections of water vapour and solar activity.<ref>{{Cite journal |last1=McCord |first1=Thomas B. |last2=Combe |first2=Jean-Philippe |last3=Castillo-Rogez |first3=Julie C. |last4=McSween |first4=Harry Y. |last5=Prettyman |first5=Thomas H. |date=May 2022 |title=Ceres, a wet planet: The view after Dawn |journal=Geochemistry |language=en |volume=82 |issue=2 |article-number=125745 |doi=10.1016/j.chemer.2021.125745|bibcode=2022ChEG...82l5745M |doi-access=free }}</ref> Water ice can migrate from the deep layers of Ceres to the surface, but it escapes in a short time. Surface sublimation would be expected to be lower when Ceres is farther from the Sun in its orbit, and internally powered emissions should not be affected by its orbital position. The limited data previously available suggested cometary-style sublimation,<ref name="Kuppers2014" /> but evidence from ''Dawn'' suggests geologic activity could be at least partially responsible.<ref>{{Cite journal |last1=Hiesinger |first1=H. |last2=Marchi |first2=S. |last3=Schmedemann |first3=N. |last4=Schenk |first4=P. |last5=Pasckert |first5=J. H. |last6=Neesemann |first6=A. |last7=OBrien |first7=D. P. |last8=Kneissl |first8=T. |last9=Ermakov |first9=A. I. |last10=Fu |first10=R. R. |last11=Bland |first11=M. T. |date=1 September 2016 |title=Cratering on Ceres: Implications for its crust and evolution |journal=Science |volume=353 |issue=6303 |article-number=aaf4759 |bibcode=2016Sci...353.4759H |doi=10.1126/science.aaf4759 |pmid=27701089 |doi-access=free |last12=Nathues |first12=A. |last13=Platz |first13=T. |last14=Williams |first14=D. A. |last15=Jaumann |first15=R. |last16=Castillo-Rogez |first16=J. C. |last17=Ruesch |first17=O. |last18=Schmidt |first18=B. |last19=Park |first19=R. S. |last20=Preusker |first20=F. |last21=Buczkowski |first21=D. L. |last22=Russell |first22=C. T. |last23=Raymond |first23=C. A.}}</ref>

Studies using ''Dawn's'' gamma ray and neutron detector (GRaND) reveal that Ceres accelerates electrons from the solar wind; the most accepted hypothesis is that these electrons are being accelerated by collisions between the solar wind and a tenuous water vapour exosphere.<ref>{{Cite web |last=NASA/Jet Propulsion Laboratory |date=1 September 2016 |title=Ceres' geological activity, ice revealed in new research |url=https://www.sciencedaily.com/releases/2016/09/160901155103.htm |url-status=live |archive-url=https://web.archive.org/web/20170405062528/https://www.sciencedaily.com/releases/2016/09/160901155103.htm |archive-date=5 April 2017 |access-date=8 March 2017 |website=ScienceDaily}}</ref><ref name=":0">{{Cite journal |last1=Russell |first1=C. T. |last2=Raymond |first2=C. A. |last3=Ammannito |first3=E. |last4=Buczkowski |first4=D. L. |last5=De Sanctis |first5=M. C. |last6=Hiesinger |first6=H. |last7=Jaumann |first7=R. |last8=Konopliv |first8=A. S. |last9=McSween |first9=H. Y. |last10=Nathues |first10=A. |last11=Park |first11=R. S. |date=2 September 2016 |title=Dawn arrives at Ceres: Exploration of a small, volatile-rich world |journal=Science |volume=353 |issue=6303 |pages=1008–1010 |doi=10.1126/science.aaf4219 |pmid=27701107 |bibcode=2016Sci...353.1008R |doi-access=free }}</ref> [[Bow shock]]s like these could also be explained by a transient magnetic field, but this is considered less likely, as the interior of Ceres is not thought to be sufficiently electrically conductive.<ref name=":0" /> Ceres's thin exosphere is continuously replenished through exposure of water ice patches by impacts, water ice diffusion through the porous ice crust and proton sputtering during solar activity.<ref>{{Cite journal |last1=Schorghofer |first1=Norbert |last2=Byrne |first2=Shane |last3=Landis |first3=Margaret E. |last4=Mazarico |first4=Erwan |last5=Prettyman |first5=Thomas H. |last6=Schmidt |first6=Britney E. |last7=Villarreal |first7=Michaela N. |last8=Castillo-Rogez |first8=Julie |last9=Raymond |first9=Carol A. |last10=Russell |first10=Christopher T. |date=20 November 2017 |title=The Putative Cerean Exosphere |journal=The Astrophysical Journal |volume=850 |issue=1 |page=85 |doi=10.3847/1538-4357/aa932f |doi-access=free |bibcode=2017ApJ...850...85S |hdl=10150/626261 |hdl-access=free }}</ref><ref name="Schörghofer 74" /><ref name="nature12918">{{Cite journal |last1=Küppers |first1=Michael |last2=O'Rourke |first2=Laurence |last3=Bockelée-Morvan |first3=Dominique |last4=Zakharov |first4=Vladimir |last5=Lee |first5=Seungwon |last6=von Allmen |first6=Paul |last7=Carry |first7=Benoît |last8=Teyssier |first8=David |last9=Marston |first9=Anthony |last10=Müller |first10=Thomas |last11=Crovisier |first11=Jacques |last12=Barucci |first12=M. Antonietta |last13=Moreno |first13=Raphael |date=January 2014 |title=Localized sources of water vapour on the dwarf planet (1) Ceres |journal=Nature |language=en |volume=505 |issue=7484 |pages=525–527 |doi=10.1038/nature12918 |pmid=24451541 |bibcode=2014Natur.505..525K }}</ref> The rate of this vapour diffusion scales with grain size<ref>{{Cite journal |last1=Prettyman |first1=T. H. |last2=Yamashita |first2=N. |last3=Toplis |first3=M. J. |last4=McSween |first4=H. Y. |last5=Schörghofer |first5=N. |last6=Marchi |first6=S. |last7=Feldman |first7=W. C. |last8=Castillo-Rogez |first8=J. |last9=Forni |first9=O. |last10=Lawrence |first10=D. J. |last11=Ammannito |first11=E. |last12=Ehlmann |first12=B. L. |last13=Sizemore |first13=H. G. |last14=Joy |first14=S. P. |last15=Polanskey |first15=C. A. |date=6 January 2017 |title=Extensive water ice within Ceres' aqueously altered regolith: Evidence from nuclear spectroscopy |journal=Science |language=en |volume=355 |issue=6320 |pages=55–59 |doi=10.1126/science.aah6765 |pmid=27980087 |bibcode=2017Sci...355...55P }}</ref> and is heavily affected by a global dust mantle consisting of an aggregate of approximately 1 micron particles.<ref>{{Cite journal |last1=Rivkin |first1=Andrew S. |last2=Li |first2=Jian-Yang |last3=Milliken |first3=Ralph E. |last4=Lim |first4=Lucy F. |last5=Lovell |first5=Amy J. |last6=Schmidt |first6=Britney E. |last7=McFadden |first7=Lucy A. |last8=Cohen |first8=Barbara A. |date=1 December 2011 |title=The Surface Composition of Ceres |journal=Space Science Reviews |language=en |volume=163 |issue=1 |pages=95–116 |doi=10.1007/s11214-010-9677-4 |bibcode=2011SSRv..163...95R }}</ref> Exospheric replenishment through sublimation alone is very small, with the current outgassing rate being only 0.003&nbsp;kg/s.<ref name="Schörghofer 74">{{Cite journal |last1=Schörghofer |first1=Norbert |last2=Benna |first2=Mehdi |last3=Berezhnoy |first3=Alexey A. |last4=Greenhagen |first4=Benjamin |last5=Jones |first5=Brant M. |last6=Li |first6=Shuai |last7=Orlando |first7=Thomas M. |last8=Prem |first8=Parvathy |last9=Tucker |first9=Orenthal J. |last10=Wöhler |first10=Christian |date=1 September 2021 |title=Water Group Exospheres and Surface Interactions on the Moon, Mercury, and Ceres |journal=Space Science Reviews |volume=217 |issue=6 |page=74 |doi=10.1007/s11214-021-00846-3 |bibcode=2021SSRv..217...74S |doi-access=free }}</ref> Various models of an extant exosphere have been attempted including ballistic trajectory, [[Direct simulation Monte Carlo|DSMC]], and polar cap numerical models.<ref>{{Cite journal |last1=Tu |first1=L. |last2=Ip |first2=W. -H. |last3=Wang |first3=Y. -C. |date=1 December 2014 |title=A Sublimation-driven Exospheric Model of Ceres |journal=Planetary and Space Science |volume=104 |pages=157–162 |doi=10.1016/j.pss.2014.09.002 |bibcode=2014P&SS..104..157T }}</ref><ref name="nature12918" /><ref>{{Cite journal |last1=Hayne |first1=P. O. |last2=Aharonson |first2=O. |date=September 2015 |title=Thermal stability of ice on Ceres with rough topography |journal=Journal of Geophysical Research: Planets |language=en |volume=120 |issue=9 |pages=1567–1584 |doi=10.1002/2015JE004887 |bibcode=2015JGRE..120.1567H }}</ref> Results showed a water exosphere half-life of 7 hours from the ballistic trajectory model, an outgassing rate of 6&nbsp;kg/s with an optically thin atmosphere sustained for tens of days using a DSMC model, and seasonal polar caps formed from exosphere water delivery using the polar cap model. The mobility of water molecules within the exosphere is dominated by ballistic hops coupled with interaction of the surface, however less is known about direct interactions with planetary regoliths.<ref name="Schörghofer 74"/>

== Origin and evolution ==
Ceres is a surviving [[protoplanet]] that formed 4.56&nbsp;billion years ago; alongside [[2 Pallas|Pallas]] and [[4 Vesta|Vesta]], one of only three remaining in the inner Solar System,<ref>{{Cite journal |last1=McCord |first1=Thomas B. |last2=McFadden |first2=Lucy A. |last3=Russell |first3=Christopher T. |last4=Sotin |first4=Christophe |last5=Thomas |first5=Peter C. |date=7 March 2006 |title=Ceres, Vesta, and Pallas: Protoplanets, Not Asteroids |journal=Eos |volume=87 |page=105 |bibcode=2006EOSTr..87..105M |doi=10.1029/2006EO100002 |number=10 }}</ref> with the rest either merging to form [[terrestrial planet]]s, being shattered in collisions<ref>{{Cite journal |last1=Yang |first1=Jijin |last2=Goldstein |first2=Joseph I. |last3=Scott |first3=Edward R. D. |name-list-style=and |year=2007 |title=Iron meteorite evidence for early formation and catastrophic disruption of protoplanets |journal=Nature |volume=446 |issue=7138 |pages=888–891 |bibcode=2007Natur.446..888Y |doi=10.1038/nature05735 |pmid=17443181 }}</ref> or being ejected by Jupiter.<ref name="Petit2001">{{Cite journal |last1=Petit |first1=Jean-Marc |last2=Morbidelli, Alessandro |year=2001 |title=The Primordial Excitation and Clearing of the Asteroid Belt |url=http://www.gps.caltech.edu/classes/ge133/reading/asteroids.pdf |url-status=live |journal=Icarus |volume=153 |issue=2 |pages=338–347 |bibcode=2001Icar..153..338P |doi=10.1006/icar.2001.6702 |archive-url=https://web.archive.org/web/20070221085835/http://www.gps.caltech.edu/classes/ge133/reading/asteroids.pdf |archive-date=21 February 2007 |access-date=25 June 2009}}</ref> Despite Ceres's current location, its composition is not consistent with having formed within the asteroid belt. It seems rather that it formed between the orbits of Jupiter and Saturn, and was deflected into the asteroid belt as Jupiter migrated outward.<ref name="Dawn2017" /> The discovery of ammonium salts in Occator Crater supports an origin in the outer Solar System, as ammonia is far more abundant in that region.<ref>{{Cite web |last=Greicius |first=Tony |date=29 June 2016 |title=Recent Hydrothermal Activity May Explain Ceres' Brightest Area |url=https://www.nasa.gov/feature/jpl/recent-hydrothermal-activity-may-explain-ceres-brightest-area/ |url-status=live |archive-url=https://web.archive.org/web/20190106142353/https://www.nasa.gov/feature/jpl/recent-hydrothermal-activity-may-explain-ceres-brightest-area |archive-date=6 January 2019 |access-date=26 July 2016 |website=nasa.gov}}</ref>

The early geological evolution of Ceres was dependent on the heat sources available during and after its formation: impact energy from [[planetesimal]] [[accretion (astrophysics)|accretion]] and decay of [[radionuclide]]s (possibly including short-lived [[extinct radionuclide]]s such as [[aluminium-26]]). These may have been sufficient to allow Ceres to differentiate into a rocky [[planetary core]] and icy mantle, or even a liquid water ocean,<ref name="EPSC" /> soon after its formation.<ref name="Bhatia2017" /> This ocean should have left an icy layer under the surface as it froze. The fact that ''Dawn'' found no evidence of such a layer suggests that Ceres's original crust was at least partially destroyed by later impacts thoroughly mixing the ice with the salts and silicate-rich material of the ancient seafloor and the material beneath.<ref name="EPSC" />

Ceres possesses surprisingly few large craters, suggesting that viscous relaxation and cryovolcanism have erased older geological features.<ref>{{Cite web |last=Atkinson |first=Nancy |date=26 July 2016 |title=Large Impact Craters on Ceres Have Gone Missing |url=https://www.universetoday.com/130048/large-impact-craters-ceres-gone-missing/ |url-status=live |archive-url=https://web.archive.org/web/20210515221501/https://www.universetoday.com/130048/large-impact-craters-ceres-gone-missing/ |archive-date=15 May 2021 |access-date=15 May 2021 |publisher=Universe Today}}</ref> The presence of clays and carbonates requires chemical reactions at temperatures above 50&nbsp;°C, consistent with hydrothermal activity.<ref name="liebert">{{Cite journal |last1=Castillo-Rogez |first1=Julie C. |last2=Neveu |first2=Marc |display-authors=1 |date=31 January 2020 |title=Ceres: Astrobiological Target and Possible Ocean World |journal=Astrobiology |volume=20 |pages=269–291 |bibcode=2020AsBio..20..269C |doi=10.1089/ast.2018.1999 |pmid=31904989 |doi-access=free |number=2}}</ref>

It has become considerably less geologically active over time, with a surface dominated by [[impact crater]]s; nevertheless, evidence from ''Dawn'' reveals that internal processes have continued to sculpt Ceres's surface to a significant extent<ref>{{Cite web |last=Wall |first=Mike |date=2 September 2016 |title=NASA's Dawn Mission Spies Ice Volcanoes on Ceres |url=http://www.scientificamerican.com/article/nasa-s-dawn-mission-spies-ice-volcanoes-on-ceres/ |url-status=live |archive-url=https://web.archive.org/web/20170603034829/https://www.scientificamerican.com/article/nasa-s-dawn-mission-spies-ice-volcanoes-on-ceres/ |archive-date=3 June 2017 |access-date=8 March 2017 |website=Scientific American}}</ref> contrary to predictions that Ceres's small size would have ceased internal geological activity early in its history.<ref name="Castillo-Rogez2007">{{Cite journal |last1=Castillo-Rogez |first1=J. C. |last2=McCord, T. B. |last3=Davis, A. G. |year=2007 |title=Ceres: evolution and present state |url=http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2006.pdf |url-status=live |journal=Lunar and Planetary Science |volume=XXXVIII |pages=2006–2007 |archive-url=https://web.archive.org/web/20110224014228/http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2006.pdf |archive-date=24 February 2011 |access-date=25 June 2009}}</ref>

== Habitability ==
[[File:PIA20353 Ceres Neutron Counts Reflect Hydrogen Abundance (cropped).jpg|thumb|alt=a polar image of Ceres showing dark blue across the northern hemisphere|Hydrogen concentration (blue) in the upper metre of the regolith indicating presence of water ice]]Although Ceres is not as actively discussed as a [[Planetary habitability|potential home]] for [[Microorganism|microbial]] [[extraterrestrial life]] as [[Life on Mars|Mars]], [[Europa (moon)#Habitability|Europa]], [[Enceladus#Potential habitability|Enceladus]], or [[Life on Titan|Titan]] are, it has the most water of any body in the inner Solar System after Earth,<ref name="liebert" /> and the likely brine pockets under its surface could provide habitats for life.<ref name="liebert" /> Unlike Europa or Enceladus, it does not experience [[tidal heating]], but it is close enough to the Sun and contains enough long-lived radioactive isotopes to preserve liquid water in its subsurface for extended periods.<ref name="liebert" /> The remote detection of [[organic compound]]s and the presence of water mixed with 20% [[carbon]] by mass in its near surface could provide conditions favourable to organic chemistry.<ref name="Nature 12 2018" /> Of the biochemical elements, Ceres is rich in [[carbon]], [[hydrogen]], [[oxygen]] and [[nitrogen]],<ref>{{cite journal|title=Characteristics of organic matter on Ceres from VIR/Dawn high spatial resolution spectra|journal= Monthly Notices of the Royal Astronomical Society| volume=482|issue=2|pages=2407–2421|doi=10.1093/mnras/sty2772|date= 17 October 2018|last1=De Sanctis |first1=M. C. |last2=Vinogradoff |first2=V. |last3=Raponi |first3=A. |last4=Ammannito |first4=E. |last5=Ciarniello |first5=M. |last6=Carrozzo |first6=F. G. |last7=De Angelis |first7=S. |last8=Raymond |first8=C. A. |last9=Russell |first9=C. T.|doi-access= free}}</ref> but [[phosphorus]] has yet to be detected,<ref>{{Cite web |last=Specktor |first=Brandon |date=19 January 2021 |title=Humans could move to this floating asteroid belt colony in the next 15 years, astrophysicist says |url=https://www.livescience.com/megasatellite-colony-ceres-oneill-cylinder.html |url-status=live |archive-url=https://web.archive.org/web/20210624204427/https://www.livescience.com/megasatellite-colony-ceres-oneill-cylinder.html |archive-date=24 June 2021 |access-date=23 June 2021 |publisher=Live Science }}</ref> and sulfur, despite being suggested by Hubble UV observations, was not detected by ''Dawn''.<ref name="liebert" />

== Observation and exploration ==
=== Observation ===
[[File:Ceres optimized.jpg|thumb|left|alt=a brown fuzzy sphere with some blurry bright and dark spots|An enhanced Hubble image of Ceres, the best acquired by a telescope, taken in 2004]]When in opposition near its [[perihelion]], Ceres can reach an [[apparent magnitude]] of +6.7.<ref name="Pasachoff1983">{{Cite book |last1=Menzel, Donald H. |url=https://archive.org/details/fieldguidetostar00menz_0/page/391 |title=A Field Guide to the Stars and Planets |last2=Pasachoff, Jay M. |publisher=[[Houghton Mifflin]] |year=1983 |isbn=978-0-395-34835-2 |edition=2nd |location=Boston |page=[https://archive.org/details/fieldguidetostar00menz_0/page/391 391] |url-access=registration}}</ref> This is too dim to be visible to the average [[naked eye]], but under ideal viewing conditions, keen eyes may be able to see it. Vesta is the only other asteroid that can regularly reach a similarly bright magnitude, while Pallas and [[7 Iris|7&nbsp;Iris]] do so only when both in opposition and near perihelion.<ref>{{Cite book |last=Martinez |first=Patrick |title=The Observer's Guide to Astronomy |publisher=[[Cambridge University Press]] |year=1994 |page=298 |isbn=978-0-521-37945-8 |oclc=984418486}}</ref> When in [[Conjunction (astronomy)|conjunction]], Ceres has a magnitude of around +9.3, which corresponds to the faintest objects visible with 10×50 binoculars; thus, it can be seen with such binoculars in a [[Light pollution|naturally dark]] and clear night sky around [[new moon]].<ref name="skyand" />

An [[occultation]] of the star BD+8°471 by Ceres was observed on 13 November 1984 in Mexico, Florida and across the [[Caribbean]], allowing better measurements of its size, shape and albedo.<ref name="Millis1987">{{Cite journal |last1=Millis |first1=L. R. |last2=Wasserman, L. H. |last3=Franz, O. Z. |display-authors=etal |year=1987 |title=The size, shape, density, and albedo of Ceres from its occultation of BD+8°471 |journal=Icarus |volume=72 |issue=3 |pages=507–518 |bibcode=1987Icar...72..507M |doi=10.1016/0019-1035(87)90048-0 |hdl-access=free |hdl=2060/19860021993}}</ref> On 25 June 1995, Hubble obtained ultraviolet images of Ceres with {{convert|50|km||-1|abbr=on}} resolution.<ref name="Parker2002">{{Cite journal |last1=Parker |first1=J. W. |last2=Stern, Alan S. |last3=Thomas Peter C. |display-authors=etal |year=2002 |title=Analysis of the first disk-resolved images of Ceres from ultraviolet observations with the Hubble Space Telescope |journal=The Astronomical Journal |volume=123 |issue=1 |pages=549–557 |arxiv=astro-ph/0110258 |bibcode=2002AJ....123..549P |doi=10.1086/338093 }}</ref> In 2002, the W. M. Keck Observatory obtained infrared images with {{convert|30|km||-1|abbr=on}} resolution using [[adaptive optics]].<ref name="Keck">{{Cite web |date=11 October 2006 |title=Keck Adaptive Optics Images the Dwarf Planet Ceres |url=http://www.adaptiveoptics.org/News_1006_2.html |archive-url=https://web.archive.org/web/20090818054459/http://www.adaptiveoptics.org/News_1006_2.html |archive-date=18 August 2009 |access-date=27 April 2007 |publisher=Adaptive Optics}}</ref>

Before the ''Dawn'' mission, only a few surface features had been unambiguously detected on Ceres. High-resolution [[ultraviolet]] Hubble images in 1995 showed a dark spot on its surface, which was nicknamed "Piazzi" in honour of the discoverer of Ceres.<ref name="Parker2002" /> It was thought to be a crater. Visible-light images of a full rotation taken by Hubble in 2003 and 2004 showed eleven recognisable surface features, the natures of which were undetermined.<ref name="Li2006">{{Cite journal |last1=Li |first1=Jian-Yang |last2=McFadden, Lucy A. |last3=Parker, Joel Wm. |year=2006 |title=Photometric analysis of 1 Ceres and surface mapping from HST observations |journal=Icarus |volume=182 |issue=1 |pages=143–160 |bibcode=2006Icar..182..143L |doi=10.1016/j.icarus.2005.12.012}}</ref><ref name="Hubbl12003-4">{{Cite news |date=7 September 2005 |title=Largest Asteroid May Be 'Mini Planet' with Water Ice |publisher=HubbleSite |url=https://hubblesite.org/contents/news-releases/2005/news-2005-27.html |url-status=live |access-date=20 July 2021 |archive-url=https://web.archive.org/web/20210720151550/https://hubblesite.org/contents/news-releases/2005/news-2005-27.html |archive-date=20 July 2021}}</ref> One of them corresponded to the Piazzi feature.<ref name="Li2006" /> [[Near-infrared]] images over a whole rotation, taken with adaptive optics by the Keck Observatory in 2012, showed bright and dark features moving with Ceres's rotation.<ref name="Carry2008" /> Two dark features were circular and were presumed to be craters; one was observed to have a bright central region, and the other was identified as the Piazzi feature.<ref name="Carry2008">{{Cite journal |last=Carry |first=Benoit |display-authors=etal |year=2007 |title=Near-Infrared Mapping and Physical Properties of the Dwarf-Planet Ceres |url=http://www2.keck.hawaii.edu/inst/people/conrad/nsfGrantRef/2007-arXiv-Benoit.Carry.pdf |journal=Astronomy & Astrophysics |volume=478 |issue=1 |pages=235–244 |arxiv=0711.1152 |bibcode=2008A&A...478..235C |doi=10.1051/0004-6361:20078166  |doi-access=free|archive-url=https://web.archive.org/web/20080530130946/http://www2.keck.hawaii.edu/inst/people/conrad/nsfGrantRef/2007-arXiv-Benoit.Carry.pdf |archive-date=30 May 2008 |s2cid=6723533}}</ref> ''Dawn'' eventually revealed Piazzi to be a dark region in the middle of [[Vendimia Planitia]], close to the crater [[Dantu (crater)|Dantu]], and the other dark feature to be within [[Hanami Planitia]] and close to [[Occator Crater]].<ref>{{Cite journal |last1=Houtkooper |first1=J. M. |last2=Schulze-Makuch |first2=D. |year=2017 |title=Ceres: A Frontier in Astrobiology |url=https://www.hou.usra.edu/meetings/abscicon2017/pdf/3252.pdf |url-status=live |journal=Astrobiology Science Conference |archive-url=https://web.archive.org/web/20210830232441/https://www.hou.usra.edu/meetings/abscicon2017/pdf/3252.pdf |archive-date=30 August 2021 |access-date=19 August 2021 |number=1965}}</ref>

=== ''Dawn'' mission ===
{{Main|Dawn (spacecraft)}}
[[File:Animation of Dawn trajectory around Ceres.gif|thumb|upright=1.2|alt=A great pink ellipse forms around a small green dot, which slowly gets surrounded by a mattte pink halo.|Animation of ''[[Dawn (spacecraft)|Dawn]]''{{'s}} trajectory around Ceres from 1 February 2015 to 1 February 2025<br />{{legend2|magenta| ''[[Dawn (spacecraft)|Dawn]]''}}{{·}}{{legend2| Lime |Ceres}}]] [[File:Dawn spacecraft model.png|thumb|upright=1.2|alt=Dawn seen ion drive firing|Artist's conception of [[Dawn (spacecraft)|''Dawn'' spacecraft]]]]In the early 1990s, NASA initiated the [[Discovery Program]], which was intended to be a series of low-cost scientific missions. In 1996, the program's study team proposed a high-priority mission to explore the asteroid belt using a spacecraft with an [[ion thruster]]. Funding remained problematic for nearly a decade, but by 2004, the [[Dawn (spacecraft)|''Dawn'']] vehicle passed its critical design review.<ref name="Russell2007">{{Cite journal |last1=Russell |first1=C. T. |last2=Capaccioni, F. |last3=Coradini, A. |display-authors=etal |date=October 2007 |title=Dawn Mission to Vesta and Ceres |url=http://www-ssc.igpp.ucla.edu/personnel/russell/papers/dawn_mission_vesta_ceres.pdf |url-status=live |journal=Earth, Moon, and Planets |volume=101 |issue=1–2 |pages=65–91 |bibcode=2007EM&P..101...65R |doi=10.1007/s11038-007-9151-9 |archive-url=https://web.archive.org/web/20201025132219/http://www-ssc.igpp.ucla.edu/personnel/russell/papers/dawn_mission_vesta_ceres.pdf |archive-date=25 October 2020 |access-date=13 June 2011 |s2cid=46423305}}</ref>

''Dawn'', the first space mission to visit either Vesta or Ceres, was launched on 27 September 2007. On 3 May 2011, ''Dawn'' acquired its first targeting image {{convert|1200000|km|mi|abbr=on}} from Vesta.<ref name="pr2011-138">{{Cite web |last1=Cook, Jia-Rui C. |last2=Brown, Dwayne C. |date=11 May 2011 |title=NASA's Dawn Captures First Image of Nearing Asteroid |url=https://www.nasa.gov/mission_pages/dawn/news/dawn20110511.html |url-status=live |archive-url=https://web.archive.org/web/20110514045000/http://www.nasa.gov/mission_pages/dawn/news/dawn20110511.html |archive-date=14 May 2011 |access-date=14 May 2011 |website=NASA/JPL}}</ref> After orbiting Vesta for thirteen months, ''Dawn'' used its ion thruster to depart for Ceres, with gravitational capture occurring on 6 March 2015<ref name="Schenk2015-01-15">{{Cite web |last=Schenk |first=P. |date=15 January 2015 |title=Year of the 'Dwarves': Ceres and Pluto Get Their Due |url=http://www.planetary.org/blogs/guest-blogs/2015/0115-year-of-the-dwarves-ceres-and-pluto.html |url-status=live |archive-url=https://web.archive.org/web/20150221192427/http://www.planetary.org/blogs/guest-blogs/2015/0115-year-of-the-dwarves-ceres-and-pluto.html |archive-date=21 February 2015 |access-date=10 February 2015 |publisher=[[The Planetary Society]]}}</ref> at a separation of {{convert|61,000|km|abbr=on}},<ref name="Rayman2014.12.01">{{Cite web |last=Rayman |first=Marc |date=1 December 2014 |title=Dawn Journal: Looking Ahead at Ceres |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20141201-dawn-journal-looking-ahead-at-ceres.html |url-status=live |archive-url=https://web.archive.org/web/20150226155456/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20141201-dawn-journal-looking-ahead-at-ceres.html |archive-date=26 February 2015 |access-date=2 March 2015 |publisher=[[The Planetary Society]]}}</ref> four months before the ''[[New Horizons]]'' flyby of Pluto.<ref name="Rayman2014.12.01" />

The spacecraft instrumentation included a framing camera, a [[Visible spectrum|visual]] and [[infrared]] [[spectrometer]], and a [[gamma ray]] and [[neutron]] detector. These instruments examined Ceres's shape and elemental composition.<ref name="Russel2006">{{Cite journal |last1=Russel |first1=C. T. |last2=Capaccioni, F. |last3=Coradini, A. |display-authors=etal |year=2006 |title=Dawn Discovery mission to Vesta and Ceres: Present status |journal=Advances in Space Research |volume=38 |issue=9 |pages=2043–2048 |arxiv=1509.05683 |bibcode=2006AdSpR..38.2043R |doi=10.1016/j.asr.2004.12.041}}</ref> On 13 January 2015, as ''Dawn'' approached Ceres, the spacecraft took its first images at near-Hubble resolution, revealing impact craters and a small high-albedo spot on the surface. Additional imaging sessions, at increasingly better resolution, took place from February to April.<ref name="Rayman2015.01.30">{{Cite web |last=Rayman |first=Marc |date=30 January 2015 |title=Dawn Journal: Closing in on Ceres |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20150130-dawn-journal-closing-in-on-ceres.html |url-status=live |archive-url=https://web.archive.org/web/20150301124801/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20150130-dawn-journal-closing-in-on-ceres.html |archive-date=1 March 2015 |access-date=2 March 2015 |publisher=[[The Planetary Society]]}}</ref>

''Dawn''{{'}}s mission profile called for it to study Ceres from a series of circular polar orbits at successively lower altitudes. It entered its first observational orbit ("RC3") around Ceres at an altitude of {{convert|13,500|km|abbr=on}} on 23 April 2015, staying for only one orbit (15 days).<ref name="Rayman2015.03.06">{{Cite web |last=Rayman |first=Marc |date=6 March 2015 |title=Dawn Journal: Ceres Orbit Insertion! |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20150306-dawn-journal-ceres-orbit-insertion.html |url-status=live |archive-url=https://web.archive.org/web/20150308124208/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20150306-dawn-journal-ceres-orbit-insertion.html |archive-date=8 March 2015 |access-date=6 March 2015 |publisher=[[The Planetary Society]]}}</ref><ref name="Rayman2014.03.03">{{Cite web |last=Rayman |first=Marc |date=3 March 2014 |title=Dawn Journal: Maneuvering Around Ceres |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140303-dawn-journal-maneuvering-around-ceres.html |url-status=live |archive-url=https://web.archive.org/web/20150226153757/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140303-dawn-journal-maneuvering-around-ceres.html |archive-date=26 February 2015 |access-date=6 March 2015 |publisher=[[The Planetary Society]]}}</ref> The spacecraft then reduced its orbital distance to {{convert|4,400|km|abbr=on}} for its second observational orbit ("survey") for three weeks,<ref name="Rayman2014.05.07">{{Cite web |last=Rayman |first=Marc |date=30 April 2014 |title=Dawn Journal: Explaining Orbit Insertion |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140430-dawn-journal-explaining-orbit-insertion.html |url-status=live |archive-url=https://web.archive.org/web/20150226162736/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140430-dawn-journal-explaining-orbit-insertion.html |archive-date=26 February 2015 |access-date=6 March 2015 |publisher=[[The Planetary Society]]}}</ref> then down to {{convert|1,470|km|abbr=on}} ("HAMO;" high altitude mapping orbit) for two months<ref name="Rayman2014.07.01">{{Cite web |last=Rayman |first=Marc |date=30 June 2014 |title=Dawn Journal: HAMO at Ceres |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140701-dawn-journal-hamo-at-ceres.html |url-status=live |archive-url=https://web.archive.org/web/20150226161929/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140701-dawn-journal-hamo-at-ceres.html |archive-date=26 February 2015 |access-date=6 March 2015 |publisher=[[The Planetary Society]]}}</ref> and then down to its final orbit at {{convert|375|km|abbr=on}} ("LAMO;" low altitude mapping orbit) for at least three months.<ref name="Rayman2014.09.02">{{Cite web |last=Rayman |first=Marc |date=31 August 2014 |title=Dawn Journal: From HAMO to LAMO and Beyond |url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140902-dawn-journal-from-hamo-to-lamo.html |url-status=live |archive-url=https://web.archive.org/web/20150301124736/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20140902-dawn-journal-from-hamo-to-lamo.html |archive-date=1 March 2015 |access-date=6 March 2015 |publisher=[[The Planetary Society]]}}</ref> In October 2015, NASA released a true-colour portrait of Ceres made by ''Dawn''.<ref>{{Cite web |title=Dawn data from Ceres publicly released: Finally, color global portraits! |url=http://www.planetary.org/blogs/emily-lakdawalla/2015/10221314-dawn-data-from-ceres-publicly.html |url-status=live |archive-url=https://web.archive.org/web/20151109123619/http://www.planetary.org/blogs/emily-lakdawalla/2015/10221314-dawn-data-from-ceres-publicly.html |archive-date=9 November 2015 |access-date=9 November 2015 |publisher=[[The Planetary Society]]}}</ref> In 2017, ''Dawn''{{'}}s mission was extended to perform a series of closer orbits around Ceres until the [[Hydrazine#Rocket fuel|hydrazine]] used to maintain its orbit ran out.<ref>{{Cite web |date=19 October 2017 |title=Dawn Mission Extended at Ceres |url=https://www.jpl.nasa.gov/news/dawn-mission-extended-at-ceres |access-date=1 October 2021 |website=NASA/JPL-Caltech |archive-date=1 October 2021 |archive-url=https://web.archive.org/web/20211001203348/https://www.jpl.nasa.gov/news/dawn-mission-extended-at-ceres |url-status=live }}</ref>

''Dawn'' soon discovered evidence of cryovolcanism. Two distinct bright spots (or high-albedo features) inside a crater (different from the bright spots observed in earlier Hubble images)<ref name="SL-20150511">{{Cite journal |last=Plait |first=Phil |author-link=Phil Plait |date=11 May 2015 |title=The Bright Spots of Ceres Spin Into View |url=http://www.slate.com/blogs/bad_astronomy/2015/05/11/ceres_new_images_show_many_many_bright_spots.html |url-status=live |journal=[[Slate (magazine)|Slate]] |archive-url=https://web.archive.org/web/20150529062723/http://www.slate.com/blogs/bad_astronomy/2015/05/11/ceres_new_images_show_many_many_bright_spots.html |archive-date=29 May 2015 |access-date=30 May 2015}}</ref> were seen in a 19 February 2015 image, leading to speculation about a possible cryovolcanic origin<ref name="O'Neill2015.02.25">{{Cite web |last=O'Neill |first=Ian |date=25 February 2015 |title=Ceres' Mystery Bright Dots May Have Volcanic Origin |url=https://www.seeker.com/ceres-mystery-bright-dots-may-have-volcanic-origin-1769548974.html |url-status=live |archive-url=https://web.archive.org/web/20160814104158/http://www.seeker.com/ceres-mystery-bright-dots-may-have-volcanic-origin-1769548974.html |archive-date=14 August 2016 |access-date=1 March 2015 |publisher=[[Discovery, Inc.|Discovery Inc.]]}}</ref> or outgassing.<ref name="planetary.org">{{Cite web |last=Lakdawalla |first=Emily |author-link=Emily Lakdawalla |year=2015 |title=LPSC 2015: First results from Dawn at Ceres: provisional place names and possible plumes |url=http://www.planetary.org/blogs/emily-lakdawalla/2015/03191629-lpsc-2015-dawn-at-ceres.html |url-status=live |archive-url=https://web.archive.org/web/20160506035930/http://www.planetary.org/blogs/emily-lakdawalla/2015/03191629-lpsc-2015-dawn-at-ceres.html |archive-date=6 May 2016 |access-date=23 September 2021 |work=[[The Planetary Society]]}}</ref> On 2 September 2016, scientists from the ''Dawn'' team argued in a ''[[Science (journal)|Science]]'' paper that Ahuna Mons was the strongest evidence yet for cryovolcanic features on Ceres.<ref name="Ruesch2016" /> On 11 May 2015, NASA released a higher-resolution image showing that the spots were composed of multiple smaller spots.<ref>{{Cite web |date=11 May 2015 |title=Ceres RC3 Animation |url=https://www.jpl.nasa.gov/images/ceres-rc3-animation |url-status=live |archive-url=https://web.archive.org/web/20210117042828/https://www.jpl.nasa.gov/images/ceres-rc3-animation/ |archive-date=17 January 2021 |access-date=31 July 2015 |publisher=[[Jet Propulsion Laboratory]]}}</ref> On 9 December 2015, NASA scientists reported that the bright spots on Ceres may be related to a type of salt, particularly a form of brine containing magnesium sulfate hexahydrate (MgSO<sub>4</sub>·6H<sub>2</sub>O); the spots were also found to be associated with [[ammonia]]-rich clays.<ref name="NASA-20151209-el">{{Cite web |last=Landau |first=Elizabeth |date=9 December 2015 |title=New Clues to Ceres' Bright Spots and Origins |url=https://phys.org/news/2015-12-clues-ceres-bright.html |url-status=live |archive-url=https://web.archive.org/web/20151209215813/http://phys.org/news/2015-12-clues-ceres-bright.html |archive-date=9 December 2015 |access-date=10 December 2015 |publisher=[[phys.org]]}}</ref> In June 2016, near-infrared spectra of these bright areas were found to be consistent with a large amount of sodium carbonate ({{chem|Na|2|CO|3}}), implying that recent geologic activity was probably involved in the creation of the bright spots.<ref name="De Sanctis">{{Cite journal |last=De Sanctis |first=M. C. |display-authors=et al |date=29 June 2016 |title=Bright carbonate deposits as evidence of aqueous alteration on (1) Ceres |journal=[[Nature (journal)|Nature]] |volume=536 |issue=7614 |pages=54–57 |bibcode=2016Natur.536...54D |doi=10.1038/nature18290 |pmid=27362221 |s2cid=4465999}}</ref>

From June to October 2018, ''Dawn'' orbited Ceres from as close as {{cvt|35|km|mi}} to as far away as {{cvt|4000|km|mi}}.<ref name="NASA-20180613">{{Cite web |last=Rayman |first=Marc |date=13 June 2018 |title=Dawn – Mission Status |url=https://dawn.jpl.nasa.gov/mission/status_2018.html |url-status=live |archive-url=https://web.archive.org/web/20180623200554/https://dawn.jpl.nasa.gov/mission/status_2018.html |archive-date=23 June 2018 |access-date=16 June 2018 |publisher=[[Jet Propulsion Laboratory]]}}</ref> The ''Dawn'' mission ended on 1 November 2018 after the spacecraft ran out of fuel.<ref>{{Cite web |last=Rayman |first=Marc |year=2018 |title=Dear Dawntasmagorias |url=https://www.jpl.nasa.gov/blog/2018/11/dear-dawntasmagorias |url-status=live |archive-url=https://web.archive.org/web/20210721141849/https://www.jpl.nasa.gov/blog/2018/11/dear-dawntasmagorias |archive-date=21 July 2021 |access-date=21 July 2021 |website=NASA Jet Propulsion Laboratory}}</ref>

=== Future missions ===
In 2020, an ESA team proposed the [[Calathus Mission]] concept, a followup mission to [[Occator (crater)|Occator Crater]], to [[Sample-return mission|return a sample]] of the bright carbonate faculae and dark organics to Earth.<ref name="organics 2018">{{Cite journal |author1=Kissick, L. E. |author2=Acciarini, G. |author3=Bates, H. |display-authors=etal |year=2020 |title=Sample Return From A Relic Ocean World: The Calthus Mission To Occator Crater, Ceres |url=https://www.hou.usra.edu/meetings/lpsc2020/pdf/1291.pdf |url-status=live |journal=51st Lunar and Planetary Science Conference |archive-url=https://web.archive.org/web/20201026101337/https://www.hou.usra.edu/meetings/lpsc2020/pdf/1291.pdf |archive-date=26 October 2020 |access-date=1 February 2020}}</ref> The [[China National Space Administration]] is designing a sample-return mission from Ceres that would take place during the 2020s.<ref>{{Cite web |author1=Zou, Yongliao |author2=Li, Wei |author3=Ouyang Ziyuan |title=China's Deep-space Exploration to 2030 |url=http://english.nssc.cas.cn/ns/NU/201410/W020141016603613379886.pdf |url-status=live |archive-url=https://web.archive.org/web/20141214210927/http://english.nssc.cas.cn/ns/NU/201410/W020141016603613379886.pdf |archive-date=14 December 2014 |access-date=23 September 2021 |publisher=Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing}}</ref>

== See also ==
* [[List of exceptional asteroids]]
* [[List of Solar System objects by size]]
* [[List of former planets]]

== Notes ==
{{Reflist|group=lower-alpha}}

== References ==
{{Reflist|refs=

<ref name="jpl_sbdb">{{Cite web |title=JPL Small-Body Database Browser: 1 Ceres |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Ceres |url-status=live |archive-url=https://web.archive.org/web/20210609120950/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=ceres |archive-date=9 June 2021 |access-date=26 September 2021 |publisher=JPL Solar System Dynamics}}</ref>

<ref name="AstDys-object">{{Cite web |title=Asteroid (1) Ceres – Summary |url=https://newton.spacedys.com/astdys/index.php?pc=1.1.0&n=1 |url-status=live |archive-url=https://web.archive.org/web/20200726111025/https://newton.spacedys.com/astdys/index.php?n=1&pc=1.1.0 |archive-date=26 July 2020 |access-date=15 October 2019 |publisher=AstDyS-2}}</ref>
<!--<ref name="Horizons2022">{{Cite web |title=Horizons Batch for 1 Ceres on 2022-Dec-06 |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Ceres%27&START_TIME=%272022-Dec-06%27&STOP_TIME=%272022-Dec-08%27&STEP_SIZE=%271%20hour%27&QUANTITIES=%2719%27 |url-status=live |archive-url=https://web.archive.org/web/20210929081232/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Ceres%27&START_TIME=%272022-Dec-06%27&STOP_TIME=%272022-Dec-08%27&STEP_SIZE=%271+hour%27&QUANTITIES=%2719%27 |archive-date=29 September 2021 |access-date=26 September 2021 |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]] |type=Perihelion occurs when rdot flips from negative to positive}} (Epoch 2021-Jul-01/Soln.date: 2021-Apr-13)</ref>-->
}}

== External links ==
{{Commons category|Ceres (dwarf planet)}}
*[https://trek.nasa.gov/ceres/ Ceres Trek – An integrated map browser of datasets and maps for 1&nbsp;Ceres]
*[https://solarsystem.nasa.gov/resources/2400/ceres-3d-model/ Ceres 3D Model – NASA]
*[https://www.youtube.com/watch?v=XJYfeZoHbzU Destination Ceres:Breakfast at Dawn – NASA]
*[http://dawn.jpl.nasa.gov/ ''Dawn'' mission home page] at JPL
*[http://orbitsimulator.com/gravity/articles/ceres.html Simulation of the orbit of Ceres]
*[https://www.google.com/maps/space/ceres/@18.4654488,-119.2804374,11484597m/ Google Ceres 3D], interactive map of the dwarf planet
*[http://www.keplersdiscovery.com/Asteroid.html How Gauss determined the orbit of Ceres] {{Webarchive|url=https://web.archive.org/web/20080414165827/http://www.keplersdiscovery.com/Asteroid.html |date=14 April 2008 }} from keplersdiscovery.com
*[http://imgur.com/4B1TfHg Animated reprojected colourised map of Ceres] (22 February 2015)
*{{YouTube|-JN98N6ZYU8|Video (3:34): Ceres "Bright Spots" – Mystery solved (10 August 2020)}}
*[https://www.flickr.com/photos/136797589@N04/36035176992/ Rotating relief model] of Ceres by Seán Doran (about 60% of a full rotation; starts with Occator midway above centre)
*{{AstDys|1}}
*{{JPL small body}}
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[[Category:Ceres (dwarf planet)| ]]
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