1 Ceres
⚳
Ceres - RC3 - Haulani Crater (22381131691) (cropped).jpg
Ceres in true colour in 2015
Discovery[1]
Discovered byGiuseppe Piazzi
Discovery date1 January 1801
Designations
1 Ceres
Pronunciation/ˈsɪərz/
Named after
Cerēs
AdjectivesCererian, -ean (/sɪˈrɪəriən/)
Orbital characteristics[4]
Epoch 21 January 2022 (JD 2459600.5 )
Aphelion2.98 AU (446 million km)
Perihelion2.55 AU (381 million km)
2.77 AU (414 million km)
Eccentricity0.0785
  • 4.60 yr
  • 1680 d
17.9 km/s
291.4°
Inclination
80.3°
7 December 2022
73.6°
Proper orbital elements[5]
2.77 AU
0.116
9.65°
78.2 deg / yr
4.60358 yr
(1681.458 d)
Precession of perihelion
54.1 arcsec / yr
Precession of the ascending node
−59.2 arcsec / yr
Physical characteristics
Dimensions(964.4 × 964.2 × 891.8) ± 0.2 km[4]
Mean diameter
939.4±0.2 km[4]
Mean radius
469.73 km[6]
2,770,000 km2[a]
Volume434,000,000 km3[7]
Mass
Mean density
2.162±0.008 g/cm3[4]
Equatorial surface gravity
0.36±0.15[8][b] (estimate)
Equatorial escape velocity
0.51 km/s[7]
9.074170±0.000001 h[4]
Equatorial rotation velocity
92.61 m/s[7]
≈4°[10]
North pole right ascension
291.42744°[11]
North pole declination
66.76033°[6]
0.090±0.0033 (V-band)[12]
Surface temp. min mean max
Kelvin ≈110[16] 235±4[17]
C[13]
3.34[4]
0.854″ to 0.339″

Ceres (/ˈsɪərz/;[18] minor-planet designation: 1 Ceres) is a dwarf planet in the asteroid belt between the orbits of Mars and Jupiter. It was the first asteroid 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 a dwarf planet – the only one always inside Neptune's orbit.

Ceres's 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 (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 approached Ceres for its orbital mission in 2015.

Dawn found Ceres's surface to be a mixture of water ice, and hydrated minerals such as carbonates and clay. Gravity data suggest Ceres to be partially differentiated into a muddy (ice-rock) mantle/core and a less dense but stronger crust that is at most 30% ice by volume. Although Ceres likely lacks an internal ocean of liquid water, brines still flow through the outer mantle and reach the surface, allowing cryovolcanoes such as Ahuna Mons to form roughly every fifty million years. This makes Ceres the closest known cryovolcanic body to the Sun, and the brines provide a potential habitat for microbial life.

In January 2014, emissions of water vapour were detected around Ceres, creating a tenuous, transient atmosphere known as an exosphere.[19] This was unexpected because vapour is usually a hallmark of comets, not asteroids.

History

Discovery

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 astronomer Johannes Kepler believed that the ratios between planetary orbits would conform to "God's design" only with the addition of two planets: one between Jupiter and Mars and one between Venus and Mercury.[20] Other theoreticians, 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?"[20]

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.[20][21] This formula predicted that there ought to be another planet with an orbital radius near 2.8 astronomical units (AU), or 420 million km, from the Sun.[21] The Titius–Bode law gained more credence with William Herschel's 1781 discovery of Uranus near the predicted distance for a planet beyond Saturn.[20] In 1800 a group headed by Franz Xaver von Zach, editor of the German astronomical journal Monatliche Correspondenz [de] ("Monthly Correspondence"), sent requests to 24 experienced astronomers, whom he dubbed the "celestial police",[21] asking that they combine their efforts and begin a methodical search for the expected planet.[21] Although they did not discover Ceres, they later found the asteroids Pallas, Juno, and Vesta.[21]

One of the astronomers selected for the search was Giuseppe Piazzi, a Catholic priest at the Academy of Palermo, Sicily. Before receiving his invitation to join the group, Piazzi discovered Ceres on 1 January 1801.[22] He was searching for "the 87th [star] of the Catalogue of the Zodiacal stars of Mr la Caille",[20] but found that "it was preceded by another".[20] Instead of a star, Piazzi had found a moving star-like object, which he first thought was a comet.[23] Piazzi observed Ceres 24 times, the final time 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.[24] 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".[20] 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 Monatliche Correspondenz.[23]

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 exact position. To recover Ceres, mathematician Carl Friedrich Gauss, then 24 years old, developed an efficient method of orbit determination.[23] Within a few weeks, he predicted the path of Ceres and sent his results to von Zach. On 31 December 1801, von Zach and fellow celestial policeman Heinrich W. M. Olbers found Ceres near the predicted position and continued to record its position.[23] 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.[25]

The early observers were able to calculate the size of Ceres only to within an order of magnitude. Herschel underestimated its diameter at 260 km (160 mi) in 1802; in 1811, German astronomer Johann Hieronymus Schröter overestimated it as 2,613 km (1,624 mi).[26] In the 1970s, infrared photometry enabled more accurate measurements of its albedo, and Ceres's diameter was determined to within 10% of its true value of 939 km.[26]

Name and symbol

Piazzi's proposed name for his discovery was Ceres Ferdinandea: Ceres after the 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 III of Sicily.[23] 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. 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.[27]

The adjectival forms of Ceres are Cererian[28][29] and Cererean,[30] both pronounced /sɪˈrɪəriən/.[31][32] Cerium, a rare-earth element discovered in 1803, was named after the dwarf planet Ceres.[33][c]

The old astronomical symbol of Ceres, still used in astrology, is a sickle,

⚳
.[23][35] The sickle was one of the classical symbols of the goddess Ceres and was suggested, apparently independently, by von Zach and Bode in 1802.[36] In form, it is similar 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
Ceres
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.[23][37]

Classification

Ceres (bottom left), the Moon and Earth, shown to scale
Ceres (bottom left), the Moon and Earth, shown to scale
Relative sizes of the four largest asteroids. Ceres is furthest left.
Relative sizes of the four largest minor planets in the asteroid belt (dwarf planet Ceres at left)

Main article: Geology of Ceres

The mass of 1 Ceres (blue) compared to other large asteroids: 4 Vesta, 2 Pallas, 10 Hygiea, 704 Interamnia, 15 Eunomia and the remainder of the Main Belt. The unit of mass is ×1018 kg.

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.[20] Ceres was assigned a planetary symbol and remained listed as a planet in astronomy books and tables (along with Pallas, Juno, and Vesta) for over half a century.[38]

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.[20] When Pallas was discovered in 1802, Herschel coined the term asteroid ("star-like") for these bodies,[38] writing that "they resemble small stars so much as hardly to be distinguished from them, even by very good telescopes".[39] 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. Initially, the numbering system began with the fifth asteroid, 5 Astraea, as number 1, but in 1867 Ceres was adopted into the new system under the name 1 Ceres.[38]

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 yet to be precisely defined.[38] 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.[40] 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.[41] 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".[42] Had this resolution been adopted, it would have made Ceres the fifth planet in order from the Sun,[43] but on 24 August 2006 the assembly adopted the additional requirement that a planet must have "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 40% of the belt's total mass.[44] Bodies that met the first proposed definition but not the second, such as Ceres, were instead classified as dwarf planets.[44] Planetary geologists still often ignore this definition and consider Ceres to be a planet anyway.[45]

Ceres is a dwarf planet, but there is some confusion about whether it is also an asteroid. A NASA webpage states that Vesta, the belt's second-largest object, is the largest asteroid.[46] The IAU has been equivocal on the subject,[47][48] though its Minor Planet Center, the organisation charged with cataloguing such objects, notes that dwarf planets may have dual designations,[49] and the joint IAU/USGS/NASA Gazetteer categorizes Ceres as both asteroid and a dwarf planet.[50]

Orbit

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.
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 (year) of 4.6 Earth years.[4] Compared to other planets and dwarf planets, Ceres's orbit is moderately tilted relative to that of Earth; its inclination (i) is 10.6°, compared to 7° for Mercury and 17° for Pluto. It is also slightly elongated, with an eccentricity (e) = 0.08, compared to 0.09 for Mars.[4]

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 sublimated to nothing over the age of the Solar System.[51] It was once thought to be a member of the Gefion family,[52] 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[52] and appears to be an interloper, having similar orbital elements but not a common origin.[53]

Resonances

Due to their small masses and large separations, objects within the asteroid belt rarely fall into gravitational resonances with each other.[54] Nevertheless, Ceres is able to capture other asteroids into temporary 1:1 resonances (making them temporary trojans), for periods from a few hundred thousand to more than two million years. Fifty such objects have been identified.[55] Ceres is close to a 1:1 mean-motion orbital resonance with Pallas (their proper orbital periods differ by 0.2%), but not close enough to be significant over astronomical timescales.[56]

Rotation and axial tilt

Permanently shadowed regions capable of accumulating surface ice

The rotation period of Ceres (the Cererian day) is 9 hours and 4 minutes;[10] the small equatorial crater of Kait is selected as its prime meridian.[57] Ceres has an axial tilt of 4°,[10] small enough for its polar regions to contain permanently shadowed craters that are expected to act as cold traps and accumulate water ice over time, similar to what occurs on the Moon and 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.[10]

Dawn, the first spacecraft to orbit Ceres, determined that the north polar axis points at right ascension 19 h 25 m 40.3 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.[58] Over the course of three million years, gravitational influence from Jupiter and Saturn 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.[59]

Geology

Ceres is the largest asteroid in the main asteroid belt.[13] It has been classified as a C‑type or carbonaceous asteroid[13] and, due to the presence of clay minerals, as a G-type asteroid.[60] It has a similar, but not identical, composition to that of carbonaceous chondrite meteorites.[61] It is an oblate spheroid, with an equatorial diameter 8% larger than its polar diameter.[4] Measurements from the Dawn spacecraft found a mean diameter of 939.4 km (583.7 mi)[4] and a mass of 9.38×1020 kg.[62] This gives Ceres a density of 2.16 g/cm3,[4] suggesting that a quarter of its mass is water ice.[63]

Ceres comprises 40% of the estimated (2394±5)×1018 kg mass of the asteroid belt, and it has 3+12 times the mass of the next asteroid, Vesta, but it is only 1.3% the mass of the Moon. It is close to being in hydrostatic equilibrium, but some deviations from an equilibrium shape have yet to be explained.[64] Assuming it is in equilibrium, Ceres is the only dwarf planet that is always within the orbit of Neptune.[63] Modelling has suggested Ceres's rocky material is partially differentiated, and that it may possess a small core,[65][66] but the data are also consistent with a mantle of hydrated silicates and no core.[64] Because Dawn lacked a magnetometer, it is not known if Ceres has a magnetic field; it is believed not to.[67][68] 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.[69]

Surface

Main article: List of geological features on Ceres

Composition

The surface composition of Ceres is homogeneous on a global scale, and is rich in carbonates and ammoniated phyllosilicates that have been altered by water,[64] though water ice in the regolith varies from approximately 10% in polar latitudes to much drier, even ice-free, in the equatorial regions.[64]

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 under Cererian conditions and would be expected to either escape quickly or settle in cold traps, and so are evidently associated with areas with relatively recent geological activity.[70]

Organic compounds were detected in Ernutet Crater,[71] and most of the planet's near surface is rich in carbon, at approximately 20% by mass.[72] The carbon content is more than five times higher than in carbonaceous chondrite meteorites analysed on Earth.[72] The surface carbon shows evidence of being mixed with products of rock-water interactions, such as clays.[72] 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.[72]

Craters

Topographic map of Ceres. The lowest crater floors (indigo), and the highest peaks (white) represent a difference of 15 km (10 mi) elevation.[74] "Ysolo Mons" has been renamed "Yamor Mons."[73]
Topographic map of Ceres. The lowest crater floors (indigo), and the highest peaks (white) represent a difference of 15 km (10 mi) elevation.[74] "Ysolo Mons" has been renamed "Yamor Mons."[73]

Dawn revealed that Ceres has a heavily cratered surface, though with fewer large craters than expected.[75] Models based on the formation of the current asteroid belt had predicted Ceres should have ten to fifteen craters larger than 400 km (250 mi) in diameter.[75] The largest confirmed crater on Ceres, Kerwan Basin, is 284 km (176 mi) across.[76] The most likely reason for this is viscous relaxation of the crust slowly flattening out larger impacts.[75]

Ceres's north polar region shows far more cratering than the equatorial region, with the eastern equatorial region in particular comparatively lightly cratered.[77] The overall size frequency of craters of between twenty and a hundred kilometres (10–60 mi) is consistent with their having originated in the Late Heavy Bombardment, with craters outside the ancient polar regions likely erased by early cryovolcanism.[77] Three large shallow basins (planitiae) with degraded rims are likely to be eroded craters.[64] The largest, Vendimia Planitia, at 800 km (500 mi) across,[75] is also the largest single geographical feature on Ceres.[78] Two of the three have higher than average ammonium concentrations.[64]

Dawn observed 4,423 boulders larger than 105 m (344 ft) 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 million years, much shorter than the lifetime of boulders on Vesta.[79]

Tectonic features

Although Ceres lacks plate tectonics,[80] with the vast majority of its surface features linked either to impacts or to cryovolcanic activity,[81] 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 chains, which are indicative of buried normal faults. Also, several craters on Ceres have shallow, fractured floors consistent with cryomagmatic intrusion.[82]

Cryovolcanism

Main article: Bright spots on Ceres

A smooth-sided mountain rising from a grey surface
Ahuna Mons is an estimated 5 km (3 mi) high on its steepest side.[83]
Icy patches against a grey, flat background
Cerealia and Vinalia Faculae

Ceres has one prominent mountain, Ahuna Mons; this appears to be a cryovolcano and has few craters, suggesting a maximum age of 240 million years.[84] 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 diapirism of a slurry of brine and silicate particles from the top of the mantle.[51] 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.[85] Kerwan too shows evidence of the effects of liquid water due to impact-melting of subsurface ice.[76]

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.[84][86] 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.[81] Models suggest that, over the past billion years, one cryovolcano has formed on Ceres on average every fifty million years.[81] The eruptions are not uniformly distributed over Ceres, but may be linked to ancient impact basins.[81] 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.[84]

An unexpectedly large number of Cererian craters have central pits, perhaps due to cryovolcanic processes; others have central peaks.[87] Hundreds of bright spots (faculae) have been observed by Dawn, the brightest in the middle of 80 km (50 mi) Occator Crater.[88] The bright spot in the centre of Occator is named Cerealia Facula,[89] and the group of bright spots to its east, Vinalia Faculae.[90] Occator possesses a pit 9–10 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 pingos in Earth's Arctic region.[91][92] A haze periodically appears above Cerealia, supporting the hypothesis that some sort of outgassing or sublimating ice formed the bright spots.[93] In March 2016 Dawn found definitive evidence of water ice on the surface of Ceres at Oxo crater.[94]

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 (MgSO4·6H2O); the spots were also found to be associated with ammonia-rich clays.[95] Near-infrared spectra of these bright areas were reported in 2017 to be consistent with a large amount of sodium carbonate (Na
2
CO
3
) and smaller amounts of ammonium chloride (NH
4
Cl
) or ammonium bicarbonate (NH
4
HCO
3
).[96][97] These materials have been suggested to originate from the crystallisation of brines that reached the surface.[98] 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[99] causing "bright spots", including those in Occator Crater.[100]

Internal structure

Three-layer model of Ceres's internal structure: Thick outer crust (ice, salts, hydrated minerals)Salt-rich liquid (brine) and rock"Mantle" (hydrated rock)
Three-layer model of Ceres's internal structure:
  • 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.[16]

Ceres's largest craters are several kilometres deep, inconsistent with an ice-rich shallow subsurface. The fact that the surface has preserved craters almost 300 km (200 mi) in diameter indicates that the outermost layer of Ceres is roughly 1000 times stronger than water ice. This is consistent with a mixture of silicates, hydrated salts and methane clathrates, with no more than 30% water ice by volume.[64][101]

Gravity measurements from Dawn have generated three competing models for Ceres's interior.[16] In the three-layer model Ceres is thought to consist of an outer, 40 km (25 mi) thick crust of ice, salts and hydrated minerals and an inner muddy "mantle" of hydrated rock, such as clays, separated by a 60 km (37 mi) layer of a muddy mixture of brine and rock.[102] It is not possible to tell if Ceres's deep interior contains liquid or a core of dense material rich in metal,[103] but the low central density suggests it may retain about 10% porosity.[16] One study estimated the densities of the core and mantle/crust to be 2.46–2.90 and 1.68–1.95 g/cm3 respectively, with the mantle and crust together being 70–190 km (40–120 mi) 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.[9] 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 100 km (60 mi). The solid outer crust, 40 km (25 mi) 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 100 km (60 mi) limit of detection. Under that is thought to be a mantle dominated by hydrated rocks such as clays.[103]

In one two-layer model Ceres consists of a core of chondrules 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, 360 km (220 mi) core of 75% chondrules and 25% particulates and a mantle of 75% ice and 25% particulates, to a small, 85 km (55 mi) 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 110 km (68 mi). In the latter case a 2% freezing of the liquid reservoir would compress the liquid enough to force some to the surface, producing cryovolcanism.[104]

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/cm3), the crust would be approximately 70 km (40 mi) thick and have a density of 1.68 g/cm3; with CM-class meteorites (density 2.9 g/cm3), the crust would be approximately 190 km (120 mi) thick and have a density of 1.9 g/cm3. Best-fit modelling yields a crust approximately 40 km (25 mi) thick with a density of approximately 1.25 g/cm3, and a mantle/core density of approximately 2.4 g/cm3.[64]

Atmosphere

In 2017 Dawn confirmed that Ceres has a transient atmosphere of water vapour.[105] 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 60 km (40 mi) in diameter, which each give off approximately 1026 molecules (3 kg) of water per second.[106][107][d] 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 Keck Observatory. Possible mechanisms for the vapour release are sublimation from approximately 0.6 km2 (0.2 sq mi) of exposed surface ice, cryovolcanic eruptions resulting from radiogenic internal heat,[106] or pressurisation of a subsurface ocean due to thickening of an overlying layer of ice.[110] In 2015 David Jewitt included Ceres in his list of active asteroids.[111] Surface water ice is unstable at distances less than 5 AU from the Sun,[112] so it is expected to sublime if exposed directly to solar radiation. Water ice can migrate from the deep layers of Ceres to the surface, but 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,[106] but evidence from Dawn suggests geologic activity could be at least partially responsible.[113]

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.[114][115] Bow shocks 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.[115]

Origin and evolution

Ceres is a surviving protoplanet that formed 4.56 billion years ago; alongside Pallas and Vesta, one of only three remaining in the inner Solar System,[116] with the rest either merging to form terrestrial planets, being shattered in collisions[117] or being ejected by Jupiter.[118] 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.[16] 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.[119]

The early geological evolution of Ceres was dependent on the heat sources available during and after its formation: impact energy from planetesimal accretion and decay of radionuclides (possibly including short-lived extinct radionuclides such as aluminium-26). These may have been sufficient to allow Ceres to differentiate into a rocky core and icy mantle, or even a liquid water ocean,[64] soon after its formation.[66] 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.[64]

Ceres possesses surprisingly few large craters, suggesting that viscous relaxation and cryovolcanism have erased older geological features.[120] The presence of clays and carbonates requires chemical reactions at temperatures above 50 °C, consistent with hydrothermal activity.[51]

It has become considerably less geologically active over time, with a surface dominated by impact craters; nevertheless, evidence from Dawn reveals that internal processes have continued to sculpt Ceres's surface to a significant extent[121] contrary to predictions that Ceres's small size would have ceased internal geological activity early in its history.[122]

Habitability

Hydrogen concentration (blue) in the upper metre of the regolith indicating presence of water ice
Hydrogen concentration (blue) in the upper metre of the regolith indicating presence of water ice

Although Ceres is not as actively discussed as a potential home for microbial extraterrestrial life as Mars, Europa, Enceladus, or Titan are, it has the most water of any body in the inner Solar System after Earth,[51] and the likely brine pockets under its surface could provide habitats for life.[51] It does not experience tidal heating, like Europa or Enceladus, 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.[51] The remote detection of organic compounds and the presence of water mixed with 20% carbon by mass in its near surface could provide conditions favourable to organic chemistry.[72] Of the biochemical elements, Ceres is rich in carbon, hydrogen, oxygen and nitrogen,[123] but phosphorus has yet to be detected,[124] and sulfur, despite being suggested by Hubble UV observations, was not detected by Dawn.[51]

Observation and exploration

Observation

An enhanced Hubble image of Ceres, the best acquired by a telescope, taken in 2004
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.[125] 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 do so only when both in opposition and near perihelion.[126] When in 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 naturally dark and clear night sky around new moon.[14]

On 13 November 1984 an occultation of the star BD+8°471 by Ceres was observed in Mexico, Florida and across the Caribbean, allowing better measurements of its size, shape and albedo.[127] On 25 June 1995 Hubble obtained ultraviolet images of Ceres with 50 km (30 mi) resolution.[60] In 2002 the Keck Observatory obtained infrared images with 30 km (20 mi) resolution using adaptive optics.[128]

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.[60] 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.[12][129] One of them corresponded to the Piazzi feature.[12] 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.[130] 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.[130] Dawn eventually revealed Piazzi to be a dark region in the middle of Vendimia Planitia, close to the crater Dantu, and the other dark feature to be within Hanami Planitia and close to Occator Crater.[131]

Dawn mission

Main article: Dawn (spacecraft)

Animation of Dawn's trajectory around Ceres from 1 February 2015 to 1 February 2025.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}   Dawn ·   Ceres
Animation of Dawn's trajectory around Ceres from 1 February 2015 to 1 February 2025
   Dawn ·   Ceres
Artist's conception of Dawn spacecraft
Artist's conception of 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 engine. Funding remained problematic for nearly a decade, but by 2004 the Dawn vehicle passed its critical design review.[132]

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 1,200,000 km (750,000 mi) from Vesta.[133] After orbiting Vesta for thirteen months, Dawn used its ion engine to depart for Ceres, with gravitational capture occurring on 6 March 2015[134] at a separation of 61,000 km (38,000 mi),[135] four months before the New Horizons flyby of Pluto.[135]

The spacecraft instrumentation included a framing camera, a visual and infrared spectrometer, and a gamma-ray and neutron detector. These instruments examined Ceres's shape and elemental composition.[136] 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.[137]

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 13,500 km (8,400 mi) on 23 April 2015, staying for only one orbit (15 days).[138][139] The spacecraft then reduced its orbital distance to 4,400 km (2,700 mi) for its second observational orbit ("survey") for three weeks,[140] then down to 1,470 km (910 mi) ("HAMO;" high altitude mapping orbit) for two months[141] and then down to its final orbit at 375 km (233 mi) ("LAMO;" low altitude mapping orbit) for at least three months.[142] In October 2015 NASA released a true-colour portrait of Ceres made by Dawn.[143] In 2017 Dawn's mission was extended to perform a series of closer orbits around Ceres until the hydrazine used to maintain its orbit ran out.[144]

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)[145] were seen in a 19 February 2015 image, leading to speculation about a possible cryovolcanic origin[146] or outgassing.[147] On 2 September 2016 scientists from the Dawn team argued in a Science paper that Ahuna Mons was the strongest evidence yet for cryovolcanic features on Ceres.[85] On 11 May 2015 NASA released a higher-resolution image showing that the spots were composed of multiple smaller spots.[148] 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 (MgSO4·6H2O); the spots were also found to be associated with ammonia-rich clays.[95] In June 2016 near-infrared spectra of these bright areas were found to be consistent with a large amount of sodium carbonate (Na
2
CO
3
), implying that recent geologic activity was probably involved in the creation of the bright spots.[149]

From June to October 2018 Dawn orbited Ceres from as close as 35 km (22 mi) to as far away as 4,000 km (2,500 mi).[150] The Dawn mission ended on 1 November 2018 after the spacecraft ran out of fuel.[151]

Future missions

In 2020, an ESA team proposed the Calathus Mission concept, a followup mission to Occator Crater, to return a sample of the bright carbonate faculae and dark organics to Earth.[152] The Chinese Space Agency is designing a sample-return mission from Ceres that would take place during the 2020s.[153]

See also

Notes

  1. ^ Calculated based on known parameters:
    • Surface area: 4πr2
    • Volume: 4/3πr3
    • Surface gravity: GM/r2
    • Escape velocity: 2GM/r
    • Rotation velocity: rotation period/circumference
  2. ^ 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.[9]
  3. ^ 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.[34]
  4. ^ This emission rate is modest compared to those calculated for the tidally driven plumes of Enceladus (a smaller body) and Europa (a larger body), 200 kg/s[108] and 7000 kg/s,[109] respectively.

References

  1. ^ Schmadel, Lutz (2003). Dictionary of minor planet names (5th ed.). Germany: Springer. p. 15. ISBN 978-3-540-00238-3. Archived from the original on 16 February 2021. Retrieved 21 January 2021.
  2. ^ "On The New Planet Ceres". A Journal of Natural Philosophy, Chemistry, and the Arts. 1802. Archived from the original on 29 May 2022. Retrieved 29 May 2022.
  3. ^ Souami, D.; Souchay, J. (July 2012). "The solar system's invariable plane". Astronomy & Astrophysics. 543: 11. Bibcode:2012A&A...543A.133S. doi:10.1051/0004-6361/201219011. A133.
  4. ^ a b c d e f g h i j k l "JPL Small-Body Database Browser: 1 Ceres". JPL Solar System Dynamics. Archived from the original on 9 June 2021. Retrieved 26 September 2021.
  5. ^ "AstDyS-2 Ceres Synthetic Proper Orbital Elements". Department of Mathematics, University of Pisa, Italy. Archived from the original on 21 November 2011. Retrieved 1 October 2011.
  6. ^ a b "Asteroid Ceres P_constants (PcK) SPICE kernel file". NASA Navigation and Ancillary Information Facility. Archived from the original on 28 July 2020. Retrieved 8 September 2019.
  7. ^ a b c d Calculated based on known parameters:
    • Surface area: 4πr2
    • Volume: 4/3πr3
    • Surface gravity: GM/r2
    • Escape velocity: 2GM/r
    • Rotation velocity: rotation period/circumference
  8. ^ Mao, X.; McKinnon, W. B. (2018). "Faster paleospin and deep-seated uncompensated mass as possible explanations for Ceres' present-day shape and gravity". Icarus. 299: 430–442. Bibcode:2018Icar..299..430M. doi:10.1016/j.icarus.2017.08.033.
  9. ^ a b Park, R. S.; Konopliv, A. S.; Bills, B. G.; Rambaux, N.; Castillo-Rogez, J. C.; Raymond, C. A.; Vaughan, A. T.; Ermakov, A. I.; Zuber, M. T.; Fu, R. R.; Toplis, M. J.; Russell, C. T.; Nathues, A.; Preusker, F. (3 August 2016). "A partially differentiated interior for (1) Ceres deduced from its gravity field and shape". Nature. 537 (7621): 515–517. Bibcode:2016Natur.537..515P. doi:10.1038/nature18955. PMID 27487219. S2CID 4459985.
  10. ^ a b c d Schorghofer, N.; Mazarico, E.; Platz, T.; Preusker, F.; Schröder, S. E.; Raymond, C. A.; Russell, C. T. (6 July 2016). "The permanently shadowed regions of dwarf planet Ceres". Geophysical Research Letters. 43 (13): 6783–6789. Bibcode:2016GeoRL..43.6783S. doi:10.1002/2016GL069368.
  11. ^ Konopliv, A.S.; Park, R.S.; Vaughan, A.T.; Bills, B.G.; Asmar, S.W.; Ermakov, A.I.; Rambaux, N.; Raymond, C.A.; Castillo-Rogez, J.C.; Russell, C.T.; Smith, D.E.; Zuber, M.T. (2018). "The Ceres gravity field, spin pole, rotation period and orbit from the Dawn radiometric tracking and optical data". Icarus. 299: 411–429. Bibcode:2018Icar..299..411K. doi:10.1016/j.icarus.2017.08.005.
  12. ^ a b c Li, Jian-Yang; McFadden, Lucy A.; Parker, Joel Wm. (2006). "Photometric analysis of 1 Ceres and surface mapping from HST observations". Icarus. 182 (1): 143–160. Bibcode:2006Icar..182..143L. doi:10.1016/j.icarus.2005.12.012.
  13. ^ a b c Rivkin, A. S.; Volquardsen, E. L.; Clark, B. E. (2006). "The surface composition of Ceres: Discovery of carbonates and iron-rich clays" (PDF). Icarus. 185 (2): 563–567. Bibcode:2006Icar..185..563R. doi:10.1016/j.icarus.2006.08.022. Archived (PDF) from the original on 28 November 2007. Retrieved 8 December 2007.
  14. ^ a b King, Bob (5 August 2015). "Let's Get Serious About Ceres". Sky & Telescope. Retrieved 25 July 2022.
  15. ^ "Asteroid (1) Ceres – Summary". AstDyS-2. Archived from the original on 26 July 2020. Retrieved 15 October 2019.
  16. ^ a b c d e JC Castillo Rogez; CA Raymond; CT Russell; Dawn Team (2017). "Dawn at Ceres: What Have We Learned?" (PDF). NASA, JPL. Archived (PDF) from the original on 8 October 2018. Retrieved 19 July 2021.
  17. ^ Tosi, F.; Capria, M. T.; et al. (2015). "Surface temperature of dwarf planet Ceres: Preliminary results from Dawn". 46th Lunar and Planetary Science Conference: 11960. Bibcode:2015EGUGA..1711960T. Retrieved 25 May 2021.
  18. ^ "Ceres". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 7 June 2020.
  19. ^ "Water Detected on Dwarf Planet Ceres | Science Mission Directorate". science.nasa.gov. Retrieved 20 November 2022.
  20. ^ a b c d e f g h i Hoskin, Michael (26 June 1992). "Bode's Law and the Discovery of Ceres". Observatorio Astronomico di Palermo "Giuseppe S. Vaiana". Archived from the original on 16 November 2007. Retrieved 5 July 2007.
  21. ^ a b c d e Hogg, Helen Sawyer (1948). "The Titius-Bode Law and the Discovery of Ceres". Journal of the Royal Astronomical Society of Canada. 242: 241–246. Bibcode:1948JRASC..42..241S. Archived from the original on 18 July 2021. Retrieved 18 July 2021.
  22. ^ Landau, Elizabeth (26 January 2016). "Ceres: Keeping Well-Guarded Secrets for 215 Years". NASA. Archived from the original on 24 May 2019. Retrieved 26 January 2016.
  23. ^ a b c d e f g Forbes, Eric G. (1971). "Gauss and the Discovery of Ceres". Journal for the History of Astronomy. 2 (3): 195–199. Bibcode:1971JHA.....2..195F. doi:10.1177/002182867100200305. S2CID 125888612. Archived from the original on 18 July 2021. Retrieved 18 July 2021.
  24. ^ Cunningham, Clifford J. (2001). The first asteroid: Ceres, 1801–2001. Star Lab Press. ISBN 978-0-9708162-1-4. Archived from the original on 29 May 2016. Retrieved 23 October 2015.
  25. ^ Nieto, Michael Martin (1972). The Titius-Bode Law of Planetary Distances: Its History and Theory. Pergamon Press. ISBN 978-1-4831-5936-2. Archived from the original on 29 September 2021. Retrieved 23 September 2021.
  26. ^ a b Hughes, David W (1994). "The Historical Unravelling of the Diameters of the First Four Asteroids". Quarterly Journal of the Royal Astronomical Society. 35: 331–344. Bibcode:1994QJRAS..35..331H. Archived from the original on 2 August 2021. Retrieved 2 August 2021.
  27. ^ Foderà Serio, G.; Manara, A.; Sicoli, P. (2002). "Giuseppe Piazzi and the Discovery of Ceres" (PDF). In W. F. Bottke Jr.; A. Cellino; P. Paolicchi; R. P. Binzel (eds.). Asteroids III. Tucson: University of Arizona Press. pp. 17–24. Archived (PDF) from the original on 16 March 2012. Retrieved 25 June 2009.
  28. ^ Rüpke, Jörg (2011). A Companion to Roman Religion. John Wiley and Sons. pp. 51–52. ISBN 978-1-4443-4131-7. Archived from the original on 15 November 2015. Retrieved 23 October 2015.
  29. ^ "Dawn Spacecraft Finds Traces of Water on Vesta". Sci-Tech Daily. 21 September 2012. Archived from the original on 23 September 2021. Retrieved 23 September 2021.
  30. ^ Rivkin, A. S.; et al. (2012). "The Surface Composition of Ceres". In Russell, Christopher; Raymond, Carol (eds.). The Dawn Mission to Minor Planets 4 Vesta and 1 Ceres. Springer. p. 109. ISBN 978-1-4614-4902-7.
  31. ^ William Thomas Thornton (2012) [1878]. "Epode 16". Word For Word From Horace. Nabu Press. p. 314. ISBN 978-1-279-56080-8.
  32. ^ W. Booth (1823). Flowers of Roman Poesy. Harvard University.
  33. ^ "Cerium: historical information". Adaptive Optics. Archived from the original on 9 April 2010. Retrieved 27 April 2007.
  34. ^ "Cerium". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  35. ^ JPL/NASA (22 April 2015). "What is a Dwarf Planet?". Jet Propulsion Laboratory. Archived from the original on 8 December 2021. Retrieved 19 January 2022.
  36. ^ Cunningham, Clifford (2015). Discovery of the First Asteroid, Ceres. Springer Intl. pp. 69, 164, 206. ISBN 978-3-319-21777-2. OCLC 1100952738.
  37. ^ Gould, B. A. (1852). "On the symbolic notation of the asteroids". Astronomical Journal. 2 (34): 80. Bibcode:1852AJ......2...80G. doi:10.1086/100212.
  38. ^ a b c d Hilton, James L. (17 September 2001). "When Did the Asteroids Become Minor Planets?". US Naval Observatory. Archived from the original on 6 November 2007. Retrieved 16 August 2006.
  39. ^ Herschel, William (6 May 1802). "Observations on the two lately discovered celestial Bodies". Philosophical Transactions of the Royal Society of London. 92: 213–232. Bibcode:1802RSPT...92..213H. doi:10.1098/rstl.1802.0010. JSTOR 107120. S2CID 115664950.
  40. ^ Metzger, Philip T.; Sykes, Mark V.; Stern, Alan; Runyon, Kirby (2019). "The Reclassification of Asteroids from Planets to Non-Planets". Icarus. 319: 21–32. arXiv:1805.04115. Bibcode:2019Icar..319...21M. doi:10.1016/j.icarus.2018.08.026. S2CID 119206487.
  41. ^ Connor, Steve (16 August 2006). "Solar system to welcome three new planets". The New Zealand Herald. Archived from the original on 19 July 2021. Retrieved 19 July 2021.
  42. ^ Gingerich, Owen; et al. (16 August 2006). "The IAU draft definition of "Planet" and "Plutons"". IAU. Archived from the original on 27 August 2008. Retrieved 27 April 2007.
  43. ^ "The IAU Draft Definition of Planets And Plutons". SpaceDaily. 16 August 2006. Archived from the original on 6 September 2009. Retrieved 27 April 2007.
  44. ^ a b "In Depth | Ceres". NASA Solar System Exploration. Archived from the original on 21 April 2019. Retrieved 21 April 2019.
  45. ^ Metzger, Philip T.; Grundy, W. M.; Sykes, Mark V.; Stern, Alan; Bell III, James F.; Detelich, Charlene E.; Runyon, Kirby; Summers, Michael (2022). "Moons are planets: Scientific usefulness versus cultural teleology in the taxonomy of planetary science". Icarus. 374: 114768. arXiv:2110.15285. Bibcode:2022Icar..37414768M. doi:10.1016/j.icarus.2021.114768. S2CID 240071005. Retrieved 8 August 2022.
  46. ^ "Science: One Mission, Two Remarkable Destinations". NASA. Archived from the original on 17 July 2020. Retrieved 14 July 2020. Asteroids range in size from Vesta – the largest at about 329 miles (530 km) in diameter ...
  47. ^ Lang, Kenneth (2011). The Cambridge Guide to the Solar System. Cambridge University Press. pp. 372, 442. ISBN 978-1-139-49417-5. Archived from the original on 26 July 2020. Retrieved 27 July 2019.
  48. ^ "Question and answers 2". IAU. Archived from the original on 30 January 2016. Retrieved 31 January 2008. Ceres is (or now we can say it was) the largest asteroid ... There are many other asteroids that can come close to the orbital path of Ceres.
  49. ^ Spahr, T. B. (7 September 2006). "MPEC 2006-R19: EDITORIAL NOTICE". Minor Planet Center. Archived from the original on 10 October 2008. Retrieved 31 January 2008. the numbering of "dwarf planets" does not preclude their having dual designations in possible separate catalogues of such bodies.
  50. ^ IAU; USGS Astrogeology Science Center; NASA. "Gazetteer of Planetary Nomenclature. Target: Ceres". Archived from the original on 13 October 2017. Retrieved 27 September 2021.
  51. ^ a b c d e f g Julie C. Castillo-Rogez; et al. (31 January 2020). "Ceres: Astrobiological Target and Possible Ocean World". Astrobiology. 20 (2): 269–291. Bibcode:2020AsBio..20..269C. doi:10.1089/ast.2018.1999. PMID 31904989.
  52. ^ a b Cellino, A.; et al. (2002). "Spectroscopic Properties of Asteroid Families" (PDF). Asteroids III. University of Arizona Press. pp. 633–643 (Table on p. 636). Bibcode:2002aste.book..633C. Archived (PDF) from the original on 28 March 2016. Retrieved 6 August 2011.
  53. ^ Kelley, M. S.; Gaffey, M. J. (1996). "A Genetic Study of the Ceres (Williams #67) Asteroid Family". Bulletin of the American Astronomical Society. 28: 1097. Bibcode:1996DPS....28.1009K.
  54. ^ Christou, A. A. (2000). "Co-orbital objects in the main asteroid belt". Astronomy and Astrophysics. 356: L71–L74. Bibcode:2000A&A...356L..71C.
  55. ^ Christou, A. A.; Wiegert, P. (January 2012). "A population of Main Belt Asteroids co-orbiting with Ceres and Vesta". Icarus. 217 (1): 27–42. arXiv:1110.4810. Bibcode:2012Icar..217...27C. doi:10.1016/j.icarus.2011.10.016. ISSN 0019-1035. S2CID 59474402.
  56. ^ Kovačević, A. B. (2011). "Determination of the mass of Ceres based on the most gravitationally efficient close encounters". Monthly Notices of the Royal Astronomical Society. 419 (3): 2725–2736. arXiv:1109.6455. Bibcode:2012MNRAS.419.2725K. doi:10.1111/j.1365-2966.2011.19919.x.
  57. ^ Marc Reyman (30 October 2015). "New Maps of Ceres Reveal Topography Surrounding Mysterious 'Bright Spots'". NASA. Retrieved 13 September 2022.
  58. ^ Russell, C. T.; Raymond, C. A.; et al. (21 July 2015). "05. Dawn Explores Ceres Results from the Survey Orbit" (PDF). NASA. Archived (PDF) from the original on 5 September 2015. Retrieved 23 September 2021.
  59. ^ "Ice in Ceres' Shadowed Craters Linked to Tilt History". NASA Solar System Exploration. 2017. Archived from the original on 15 May 2021. Retrieved 15 May 2021.
  60. ^ a b c Parker, J. W.; Stern, Alan S.; Thomas Peter C.; et al. (2002). "Analysis of the first disk-resolved images of Ceres from ultraviolet observations with the Hubble Space Telescope". The Astronomical Journal. 123 (1): 549–557. arXiv:astro-ph/0110258. Bibcode:2002AJ....123..549P. doi:10.1086/338093. S2CID 119337148.
  61. ^ McCord, Thomas B.; Zambon, Francesca (15 January 2019). "The surface composition of Ceres from the Dawn mission". Icarus. 318: 2–13. Bibcode:2019Icar..318....2M. doi:10.1016/j.icarus.2018.03.004. S2CID 125115208. Archived from the original on 20 May 2021. Retrieved 25 July 2021.
  62. ^ Rayman, Marc D. (28 May 2015). "Dawn Journal, 28 May 2015". Jet Propulsion Laboratory. Archived from the original on 30 May 2015. Retrieved 29 May 2015.
  63. ^ a b Nola Taylor Redd (23 May 2018). "Ceres: The Smallest and Closest Dwarf Planet". space.com. Archived from the original on 5 September 2021. Retrieved 25 July 2021.
  64. ^ a b c d e f g h i j Raymond, C.; Castillo-Rogez, J. C.; Park, R. S.; Ermakov, A.; et al. (September 2018). "Dawn Data Reveal Ceres' Complex Crustal Evolution" (PDF). European Planetary Science Congress. Vol. 12. Archived (PDF) from the original on 30 January 2020. Retrieved 19 July 2020.
  65. ^ Neumann, W.; Breuer, D.; Spohn, T. (2 December 2015). "Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation" (PDF). Astronomy & Astrophysics. 584: A117. Bibcode:2015A&A...584A.117N. doi:10.1051/0004-6361/201527083. Archived (PDF) from the original on 22 August 2016. Retrieved 10 July 2016.
  66. ^ a b Bhatia, G.K.; Sahijpal, S. (2017). "Thermal evolution of trans-Neptunian objects, icy satellites, and minor icy planets in the early solar system". Meteoritics & Planetary Science. 52 (12): 2470–2490. Bibcode:2017M&PS...52.2470B. doi:10.1111/maps.12952. S2CID 133957919.
  67. ^ Russell, C.T.; Villarreal, M.N.; Prettyman, T.H.; Yamashita, N. (16 May 2018). "The Solar Wind Interaction with Vesta and Ceres: Implications for their Magnetic Moments". ESA Cosmos. Retrieved 10 October 2022.
  68. ^ Nordheim, T.A.; Castillo-Rogez, J.C.; Villarreal, M.N.; Scully, J.E.C.; Costello, E.S. (1 May 2022). "The Radiation Environment of Ceres and Implications for Surface Sampling". Astrobiology. 22 (5): 509–519. Bibcode:2022AsBio..22..509N. doi:10.1089/ast.2021.0080. ISSN 1531-1074. PMID 35447049. S2CID 248323790. Archived from the original on 25 April 2022. Retrieved 22 July 2022.
  69. ^ McFadden, Lucy A.; Skillman, David R.; Memarsadeghi, N. (December 2018). "Dawn mission's search for satellites of Ceres: Intact protoplanets don't have satellites". Icarus. 316: 191–204. Bibcode:2018Icar..316..191M. doi:10.1016/j.icarus.2018.02.017. S2CID 125181684.
  70. ^ "Sulfur, Sulfur Dioxide, Graphitized Carbon Observed on Ceres". spaceref.com. 3 September 2016. Retrieved 8 September 2016.
  71. ^ Kaplan, Hannah H.; Milliken, Ralph E.; Alexander, Conel M. O’D. (21 May 2018). "New Constraints on the Abundance and Composition of Organic Matter on Ceres". Geophysical Research Letters. 45 (11): 5274–5282. Bibcode:2018GeoRL..45.5274K. doi:10.1029/2018GL077913. S2CID 51801398.
  72. ^ a b c d e Marchi, S.; Raponi, A.; Prettyman, T. H.; De Sanctis, M. C.; Castillo-Rogez, J.; Raymond, C. A.; Ammannito, E.; Bowling, T.; Ciarniello, M.; Kaplan, H.; Palomba, E.; Russell, C. T.; Vinogradoff, V.; Yamashita, N. (2018). "An aqueously altered carbon-rich Ceres". Nature Astronomy. 3 (2): 140–145. doi:10.1038/s41550-018-0656-0. S2CID 135013590.
  73. ^ a b "Name Changed on Ceres". USGS. 7 December 2016. Archived from the original on 19 August 2021. Retrieved 19 August 2021.
  74. ^ Landau, Elizabeth (28 July 2015). "New Names and Insights at Ceres". NASA. Archived from the original on 6 January 2016. Retrieved 28 July 2015.
  75. ^ a b c d Marchi, S.; Ermakov, A. I.; Raymond, C. A.; Fu, R. R.; O'Brien, D. P.; Bland, M. T.; Ammannito, E.; De Sanctis, M. C.; Bowling, T.; Schenk, P.; Scully, J. E. C.; Buczkowski, D. L.; Williams, D. A.; Hiesinger, H.; Russell, C. T. (26 July 2016). "The missing large impact craters on Ceres". Nature Communications. 7: 12257. Bibcode:2016NatCo...712257M. doi:10.1038/ncomms12257. PMC 4963536. PMID 27459197.
  76. ^ a b Williams, David A.; Kneiss, T. (December 2018). "The geology of the Kerwan quadrangle of dwarf planet Ceres: Investigating Ceres' oldest, largest impact basin". Icarus. 316: 99–113. Bibcode:2018Icar..316...99W. doi:10.1016/j.icarus.2017.08.015. S2CID 85539501. Archived from the original on 16 August 2021. Retrieved 16 August 2021.
  77. ^ a b Strom, R.G.; Marchi, S.; Malhotra, R. (2018). "Ceres and the Terrestrial Planets Impact Cratering Record" (PDF). Icarus. 302: 104–108. arXiv:1804.01229. Bibcode:2018Icar..302..104S. doi:10.1016/j.icarus.2017.11.013. S2CID 119009942. Archived (PDF) from the original on 16 April 2021. Retrieved 15 August 2021.
  78. ^ "Hanami Planum on Ceres". NASA. 23 March 2018. Archived from the original on 29 September 2021. Retrieved 17 August 2021.
  79. ^ Schröder, Stefan E; Carsenty, Uri; Hauber, Ernst; Raymond, Carol; Russell, Christopher (May 2021). "The brittle boulders of dwarf planet Ceres". Planetary Science Journal. 2 (3): 111. arXiv:2105.11841. Bibcode:2021PSJ.....2..111S. doi:10.3847/PSJ/abfe66. S2CID 235187212. Archived from the original on 26 May 2021. Retrieved 26 May 2021.
  80. ^ Stern, Robert J.; Gerya, Taras; Tackley, Paul J. (January 2018). "Stagnant lid tectonics: Perspectives from silicate planets, dwarf planets, large moons, and large asteroids". Geoscience Frontiers. 9 (1): 103–119. doi:10.1016/j.gsf.2017.06.004. Archived from the original on 19 January 2022. Retrieved 22 July 2022.
  81. ^ a b c d "Ceres takes life an ice volcano at a time". University of Arizona. 17 September 2018. Archived from the original on 9 November 2020. Retrieved 22 April 2019.
  82. ^ Buczkowski, D.; Scully, J. E. C.; Raymond, C. A.; Russell, C. T. (December 2017). "Exploring Tectonic Activity on Vesta and Ceres". American Geophysical Union, Fall Meeting 2017, Abstract #P53G-02. 2017. Bibcode:2017AGUFM.P53G..02B. Archived from the original on 29 September 2021. Retrieved 19 August 2021.
  83. ^ "PIA20348: Ahuna Mons Seen from LAMO". Jet Propulsion Lab. 7 March 2016. Archived from the original on 11 March 2016. Retrieved 14 April 2016.
  84. ^ a b c Sori, Michael T.; Sizemore, Hanna G.; et al. (December 2018). "Cryovolcanic rates on Ceres revealed by topography". Nature Astronomy. 2 (12): 946–950. Bibcode:2018NatAs...2..946S. doi:10.1038/s41550-018-0574-1. S2CID 186800298. Retrieved 17 August 2021.
  85. ^ a b Ruesch, O.; Platz, T.; Schenk, P.; McFadden, L. A.; Castillo-Rogez, J. C.; Quick, L. C.; Byrne, S.; Preusker, F.; OBrien, D. P.; Schmedemann, N.; Williams, D. A.; Li, J.- Y.; Bland, M. T.; Hiesinger, H.; Kneissl, T.; Neesemann, A.; Schaefer, M.; Pasckert, J. H.; Schmidt, B. E.; Buczkowski, D. L.; Sykes, M. V.; Nathues, A.; Roatsch, T.; Hoffmann, M.; Raymond, C. A.; Russell, C. T. (2 September 2016). "Cryovolcanism on Ceres". Science. 353 (6303): aaf4286. Bibcode:2016Sci...353.4286R. doi:10.1126/science.aaf4286. PMID 27701087.
  86. ^ Sori, Michael M.; Byrne, Shane; Bland, Michael T.; Bramson, Ali M.; Ermakov, Anton I.; Hamilton, Christopher W.; Otto, Katharina A.; Ruesch, Ottaviano; Russell, Christopher T. (2017). "The vanishing cryovolcanoes of Ceres" (PDF). Geophysical Research Letters. 44 (3): 1243–1250. Bibcode:2017GeoRL..44.1243S. doi:10.1002/2016GL072319. hdl:10150/623032. S2CID 52832191. Archived from the original on 29 September 2021. Retrieved 25 August 2019.
  87. ^ "News – Ceres Spots Continue to Mystify in Latest Dawn Images". NASA/JPL. Archived from the original on 25 July 2021. Retrieved 25 July 2021.
  88. ^ "USGS: Ceres nomenclature" (PDF). Archived (PDF) from the original on 15 November 2015. Retrieved 16 July 2015.
  89. ^ "Cerealia Facula". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  90. ^ "Vinalia Faculae". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  91. ^ Landau, Elizabeth; McCartney, Gretchen (24 July 2018). "What Looks Like Ceres on Earth?". NASA. Archived from the original on 31 May 2021. Retrieved 26 July 2021.
  92. ^ Schenk, Paul; Sizemore, Hanna; et al. (1 March 2019). "The central pit and dome at Cerealia Facula bright deposit and floor deposits in Occator Crater, Ceres: Morphology, comparisons and formation". Icarus. 320: 159–187. Bibcode:2019Icar..320..159S. doi:10.1016/j.icarus.2018.08.010. S2CID 125527752.
  93. ^ Rivkin, Andrew (21 July 2015). "Dawn at Ceres: A haze in Occator Crater?". The Planetary Society. Archived from the original on 14 May 2016. Retrieved 8 March 2017.
  94. ^ Redd, Nola Taylor. "Water Ice on Ceres Boosts Hopes for Buried Ocean [Video]". Scientific American. Archived from the original on 7 April 2016. Retrieved 7 April 2016.
  95. ^ a b Landau, Elizabeth (9 December 2015). "New Clues to Ceres' Bright Spots and Origins". phys.org. Archived from the original on 9 December 2015. Retrieved 10 December 2015.
  96. ^ Vu, Tuan H.; Hodyss, Robert; Johnson, Paul V.; Choukroun, Mathieu (July 2017). "Preferential formation of sodium salts from frozen sodium-ammonium-chloride-carbonate brines – Implications for Ceres' bright spots". Planetary and Space Science. 141: 73–77. Bibcode:2017P&SS..141...73V. doi:10.1016/j.pss.2017.04.014.
  97. ^ McCord, Thomas B.; Zambon, Francesca (2019). "The surface composition of Ceres from the Dawn mission". Icarus. 318: 2–13. Bibcode:2019Icar..318....2M. doi:10.1016/j.icarus.2018.03.004. S2CID 125115208.
  98. ^ Quick, Lynnae C.; Buczkowski, Debra L.; Ruesch, Ottaviano; Scully, Jennifer E. C.; Castillo-Rogez, Julie; Raymond, Carol A.; Schenk, Paul M.; Sizemore, Hanna G.; Sykes, Mark V. (1 March 2019). "A Possible Brine Reservoir Beneath Occator Crater: Thermal and Compositional Evolution and Formation of the Cerealia Dome and Vinalia Faculae". Icarus. 320: 119–135. Bibcode:2019Icar..320..119Q. doi:10.1016/j.icarus.2018.07.016. S2CID 125508484. Archived from the original on 29 September 2021. Retrieved 9 June 2021.
  99. ^ N.T. Stein; B.L. Ehlmann (1 March 2019). "The formation and evolution of bright spots on Ceres". Icarus. 320: 188–201. Bibcode:2019Icar..320..188S. doi:10.1016/j.icarus.2017.10.014.
  100. ^ McCartney, Gretchen (11 August 2020). "Mystery solved: Bright areas on Ceres come from salty water below". Phys.org. Archived from the original on 11 August 2020. Retrieved 12 August 2020.
  101. ^ Bland, Michael T.; Raymond, Carol A.; et al. (2016). "Composition and structure of the shallow subsurface of Ceres revealed by crater morphology". Nature Geoscience. 9 (7): 538–542. Bibcode:2016NatGe...9..538B. doi:10.1038/ngeo2743. hdl:10919/103024. Archived from the original on 15 September 2021. Retrieved 15 September 2021.
  102. ^ "Catalog Page for PIA22660". photojournal.jpl.nasa.gov. Archived from the original on 21 April 2019. Retrieved 21 April 2019.
  103. ^ a b "PIA22660: Ceres' Internal Structure (Artist's Concept)". Photojournal. Jet Propulsion Laboratory. 14 August 2018. Archived from the original on 21 April 2019. Retrieved 22 April 2019. Public Domain This article incorporates text from this source, which is in the public domain.
  104. ^ Neveu, M.; Desch, S. J. (2016). "Geochemistry, thermal evolution, and cryovolanism on Ceres with a muddy ice mantle". 47th Lunar and Planetary Science Conference. 42 (23). doi:10.1002/2015GL066375. S2CID 51756619.
  105. ^ "Confirmed: Ceres Has a Transient Atmosphere". Universe Today. 6 April 2017. Archived from the original on 15 April 2017. Retrieved 14 April 2017.
  106. ^ a b c Küppers, M.; O'Rourke, L.; Bockelée-Morvan, D.; Zakharov, V.; Lee, S.; Von Allmen, P.; Carry, B.; Teyssier, D.; Marston, A.; Müller, T.; Crovisier, J.; Barucci, M. A.; Moreno, R. (23 January 2014). "Localized sources of water vapour on the dwarf planet (1) Ceres". Nature. 505 (7484): 525–527. Bibcode:2014Natur.505..525K. doi:10.1038/nature12918. ISSN 0028-0836. PMID 24451541. S2CID 4448395.
  107. ^ Campins, H.; Comfort, C. M. (23 January 2014). "Solar system: Evaporating asteroid". Nature. 505 (7484): 487–488. Bibcode:2014Natur.505..487C. doi:10.1038/505487a. PMID 24451536. S2CID 4396841.
  108. ^ Hansen, C. J.; Esposito, L.; Stewart, A. I.; Colwell, J.; Hendrix, A.; Pryor, W.; Shemansky, D.; West, R. (10 March 2006). "Enceladus' Water Vapor Plume". Science. 311 (5766): 1422–1425. Bibcode:2006Sci...311.1422H. doi:10.1126/science.1121254. PMID 16527971. S2CID 2954801.
  109. ^ Roth, L.; Saur, J.; Retherford, K. D.; Strobel, D. F.; Feldman, P. D.; McGrath, M. A.; Nimmo, F. (26 November 2013). "Transient Water Vapor at Europa's South Pole" (PDF). Science. 343 (6167): 171–174. Bibcode:2014Sci...343..171R. doi:10.1126/science.1247051. PMID 24336567. S2CID 27428538. Archived (PDF) from the original on 16 December 2013. Retrieved 26 January 2014.
  110. ^ O'Brien, D. P.; Travis, B. J.; Feldman, W. C.; Sykes, M. V.; Schenk, P. M.; Marchi, S.; Russell, C. T.; Raymond, C. A. (March 2015). "The Potential for Volcanism on Ceres due to Crustal Thickening and Pressurisation of a Subsurface Ocean" (PDF). 46th Lunar and Planetary Science Conference. p. 2831. Archived (PDF) from the original on 5 November 2016. Retrieved 1 March 2015.
  111. ^ Jewitt, David; Hsieh, Henry; Agarwal, Jessica (2015). Michel, P.; et al. (eds.). The Active Asteroids (PDF). Asteroids IV. University of Arizona. pp. 221–241. arXiv:1502.02361. Bibcode:2015aste.book..221J. doi:10.2458/azu_uapress_9780816532131-ch012. ISBN 978-0-8165-3213-1. S2CID 119209764. Archived (PDF) from the original on 30 August 2021. Retrieved 30 January 2020.
  112. ^ Jewitt, D; Chizmadia, L.; Grimm, R.; Prialnik, D (2007). "Water in the Small Bodies of the Solar System" (PDF). In Reipurth, B.; Jewitt, D.; Keil, K. (eds.). Protostars and Planets V. University of Arizona Press. pp. 863–878. ISBN 978-0-8165-2654-3. Archived (PDF) from the original on 10 August 2017. Retrieved 11 October 2012.
  113. ^ Hiesinger, H.; Marchi, S.; Schmedemann, N.; Schenk, P.; Pasckert, J. H.; Neesemann, A.; OBrien, D. P.; Kneissl, T.; Ermakov, A. I.; Fu, R. R.; Bland, M. T.; Nathues, A.; Platz, T.; Williams, D. A.; Jaumann, R.; Castillo-Rogez, J. C.; Ruesch, O.; Schmidt, B.; Park, R. S.; Preusker, F.; Buczkowski, D. L.; Russell, C. T.; Raymond, C. A. (1 September 2016). "Cratering on Ceres: Implications for its crust and evolution". Science. 353 (6303): aaf4759. Bibcode:2016Sci...353.4759H. doi:10.1126/science.aaf4759. PMID 27701089.
  114. ^ NASA/Jet Propulsion Laboratory (1 September 2016). "Ceres' geological activity, ice revealed in new research". ScienceDaily. Archived from the original on 5 April 2017. Retrieved 8 March 2017.
  115. ^ a b Russell, C. T.; Raymond, C. A.; Ammannito, E.; Buczkowski, D. L.; De Sanctis, M. C.; Hiesinger, H.; Jaumann, R.; Konopliv, A. S.; McSween, H. Y.; Nathues, A.; Park, R. S. (2 September 2016). "Dawn arrives at Ceres: Exploration of a small, volatile-rich world". Science. 353 (6303): 1008–1010. Bibcode:2016Sci...353.1008R. doi:10.1126/science.aaf4219. ISSN 0036-8075. PMID 27701107. S2CID 33455833. Archived from the original on 30 October 2021. Retrieved 22 July 2022.
  116. ^ McCord, Thomas B.; McFadden, Lucy A.; Russell, Christopher T.; Sotin, Christophe; Thomas, Peter C. (7 March 2006). "Ceres, Vesta, and Pallas: Protoplanets, Not Asteroids". Eos. 87 (10): 105. Bibcode:2006EOSTr..87..105M. doi:10.1029/2006EO100002. Archived from the original on 28 September 2021. Retrieved 12 September 2021.
  117. ^ Jijin Yang, Joseph I. Goldstein & Edward R. D. Scott (2007). "Iron meteorite evidence for early formation and catastrophic disruption of protoplanets". Nature. 446 (7138): 888–891. Bibcode:2007Natur.446..888Y. doi:10.1038/nature05735. PMID 17443181. S2CID 4335070. Archived from the original on 29 September 2021. Retrieved 16 September 2021.
  118. ^ Petit, Jean-Marc; Morbidelli, Alessandro (2001). "The Primordial Excitation and Clearing of the Asteroid Belt" (PDF). Icarus. 153 (2): 338–347. Bibcode:2001Icar..153..338P. doi:10.1006/icar.2001.6702. Archived (PDF) from the original on 21 February 2007. Retrieved 25 June 2009.
  119. ^ Greicius, Tony (29 June 2016). "Recent Hydrothermal Activity May Explain Ceres' Brightest Area". nasa.gov. Archived from the original on 6 January 2019. Retrieved 26 July 2016.
  120. ^ Atkinson, Nancy (26 July 2016). "Large Impact Craters on Ceres Have Gone Missing". Universe Today. Archived from the original on 15 May 2021. Retrieved 15 May 2021.
  121. ^ Wall, Mike (2 September 2016). "NASA's Dawn Mission Spies Ice Volcanoes on Ceres". Scientific American. Archived from the original on 3 June 2017. Retrieved 8 March 2017.
  122. ^ Castillo-Rogez, J. C.; McCord, T. B.; Davis, A. G. (2007). "Ceres: evolution and present state" (PDF). Lunar and Planetary Science. XXXVIII: 2006–2007. Archived (PDF) from the original on 24 February 2011. Retrieved 25 June 2009.
  123. ^ De Sanctis, M. C.; Vinogradoff, V.; Raponi, A.; Ammannito, E.; Ciarniello, M.; Carrozzo, F. G.; De Angelis, S.; Raymond, C. A.; Russell, C. T. (17 October 2018). "Characteristics of organic matter on Ceres from VIR/Dawn high spatial resolution spectra". Monthly Notices of the Royal Astronomical Society. 482 (2): 2407–2421. doi:10.1093/mnras/sty2772.
  124. ^ Specktor, Brandon (19 January 2021). "Humans could move to this floating asteroid belt colony in the next 15 years, astrophysicist says". livescience.com. Archived from the original on 24 June 2021. Retrieved 23 June 2021.
  125. ^ Menzel, Donald H.; Pasachoff, Jay M. (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston: Houghton Mifflin. p. 391. ISBN 978-0-395-34835-2.
  126. ^ Martinez, Patrick (1994). The Observer's Guide to Astronomy. Cambridge University Press. p. 298. ISBN 978-0-521-37945-8. OCLC 984418486.
  127. ^ Millis, L. R.; Wasserman, L. H.; Franz, O. Z.; et al. (1987). "The size, shape, density, and albedo of Ceres from its occultation of BD+8°471". Icarus. 72 (3): 507–518. Bibcode:1987Icar...72..507M. doi:10.1016/0019-1035(87)90048-0. hdl:2060/19860021993.
  128. ^ "Keck Adaptive Optics Images the Dwarf Planet Ceres". Adaptive Optics. 11 October 2006. Archived from the original on 18 August 2009. Retrieved 27 April 2007.
  129. ^ "Largest Asteroid May Be 'Mini Planet' with Water Ice". HubbleSite. 7 September 2005. Archived from the original on 20 July 2021. Retrieved 20 July 2021.
  130. ^ a b Carry, Benoit; et al. (2007). "Near-Infrared Mapping and Physical Properties of the Dwarf-Planet Ceres" (PDF). Astronomy & Astrophysics. 478 (1): 235–244. arXiv:0711.1152. Bibcode:2008A&A...478..235C. doi:10.1051/0004-6361:20078166. S2CID 6723533. Archived from the original (PDF) on 30 May 2008.
  131. ^ J.M. Houtkooper, D.Schulze-Makuch (2017). "Ceres: A Frontier in Astrobiology" (PDF). Astrobiology Science Conference (1965). Archived (PDF) from the original on 30 August 2021. Retrieved 19 August 2021.
  132. ^ Russell, C. T.; Capaccioni, F.; Coradini, A.; et al. (October 2007). "Dawn Mission to Vesta and Ceres" (PDF). Earth, Moon, and Planets. 101 (1–2): 65–91. Bibcode:2007EM&P..101...65R. doi:10.1007/s11038-007-9151-9. S2CID 46423305. Archived (PDF) from the original on 25 October 2020. Retrieved 13 June 2011.
  133. ^ Cook, Jia-Rui C.; Brown, Dwayne C. (11 May 2011). "NASA's Dawn Captures First Image of Nearing Asteroid". NASA/JPL. Archived from the original on 14 May 2011. Retrieved 14 May 2011.
  134. ^ Schenk, P. (15 January 2015). "Year of the 'Dwarves': Ceres and Pluto Get Their Due". Planetary Society. Archived from the original on 21 February 2015. Retrieved 10 February 2015.
  135. ^ a b Rayman, Marc (1 December 2014). "Dawn Journal: Looking Ahead at Ceres". Planetary Society. Archived from the original on 26 February 2015. Retrieved 2 March 2015.
  136. ^ Russel, C. T.; Capaccioni, F.; Coradini, A.; et al. (2006). "Dawn Discovery mission to Vesta and Ceres: Present status". Advances in Space Research. 38 (9): 2043–2048. arXiv:1509.05683. Bibcode:2006AdSpR..38.2043R. doi:10.1016/j.asr.2004.12.041.
  137. ^ Rayman, Marc (30 January 2015). "Dawn Journal: Closing in on Ceres". Planetary Society. Archived from the original on 1 March 2015. Retrieved 2 March 2015.
  138. ^ Rayman, Marc (6 March 2015). "Dawn Journal: Ceres Orbit Insertion!". The Planetary Society. Archived from the original on 8 March 2015. Retrieved 6 March 2015.
  139. ^ Rayman, Marc (3 March 2014). "Dawn Journal: Maneuvering Around Ceres". Planetary Society. Archived from the original on 26 February 2015. Retrieved 6 March 2015.
  140. ^ Rayman, Marc (30 April 2014). "Dawn Journal: Explaining Orbit Insertion". Planetary Society. Archived from the original on 26 February 2015. Retrieved 6 March 2015.
  141. ^ Rayman, Marc (30 June 2014). "Dawn Journal: HAMO at Ceres". Planetary Society. Archived from the original on 26 February 2015. Retrieved 6 March 2015.
  142. ^ Rayman, Marc (31 August 2014). "Dawn Journal: From HAMO to LAMO and Beyond". Planetary Society. Archived from the original on 1 March 2015. Retrieved 6 March 2015.
  143. ^ "Dawn data from Ceres publicly released: Finally, color global portraits!". The Planetary Society. Archived from the original on 9 November 2015. Retrieved 9 November 2015.
  144. ^ "Dawn Mission Extended at Ceres". NASA/JPL-Caltech. 19 October 2017. Archived from the original on 1 October 2021. Retrieved 1 October 2021.
  145. ^ Plait, Phil (11 May 2015). "The Bright Spots of Ceres Spin Into View". Slate. Archived from the original on 29 May 2015. Retrieved 30 May 2015.
  146. ^ O'Neill, Ian (25 February 2015). "Ceres' Mystery Bright Dots May Have Volcanic Origin". Discovery Inc. Archived from the original on 14 August 2016. Retrieved 1 March 2015.
  147. ^ Lakdawalla, Emily (2015). "LPSC 2015: First results from Dawn at Ceres: provisional place names and possible plumes". The Planetary Society. Archived from the original on 6 May 2016. Retrieved 23 September 2021.
  148. ^ "Ceres RC3 Animation". Jet Propulsion Laboratory. 11 May 2015. Archived from the original on 17 January 2021. Retrieved 31 July 2015.
  149. ^ De Sanctis, M. C.; et al. (29 June 2016). "Bright carbonate deposits as evidence of aqueous alteration on (1) Ceres". Nature. 536 (7614): 54–57. Bibcode:2016Natur.536...54D. doi:10.1038/nature18290. PMID 27362221. S2CID 4465999.
  150. ^ Rayman, Marc (13 June 2018). "Dawn – Mission Status". Jet Propulsion Laboratory. Archived from the original on 23 June 2018. Retrieved 16 June 2018.
  151. ^ Rayman, Marc (2018). "Dear Dawntasmagorias". NASA Jet Propulsion Laboratory. Archived from the original on 21 July 2021. Retrieved 21 July 2021.
  152. ^ Kissick, L. E.; Acciarini, G.; Bates, H.; et al. (2020). "Sample Return From A Relic Ocean World: The Calthus Mission To Occator Crater, Ceres" (PDF). 51st Lunar and Planetary Science Conference. Archived (PDF) from the original on 26 October 2020. Retrieved 1 February 2020.
  153. ^ Zou, Yongliao; Li, Wei; Ouyang Ziyuan. "China's Deep-space Exploration to 2030" (PDF). Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing. Archived (PDF) from the original on 14 December 2014. Retrieved 23 September 2021.