Astronomy

What aliphatic compounds were found on Ceres, and how where they identified?

What aliphatic compounds were found on Ceres, and how where they identified?


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Los Angeles Times's article NASA's Dawn mission finds life's building blocks on dwarf planet Ceres says;

While the scientists aren't sure exactly what the compounds are, the fingerprint is characteristic of material containing carbon-hydrogen bonds, and may include components like methyl and methylene.

I've located the mentioned Science article Localized aliphatic organic material on the surface of Ceres but it is paywalled.

What was found? Is it some spectroscopic feature? Aliphatic compounds are hydrocarbons that are not aromatic. Is there a spectral feature that says "I am not aromatic" specifically, or does this just mean that aromaticity was not detected?


OK, I did a bit of research on this. The LA Times article you quoted says something a little bit useful.

While the scientists aren't sure exactly what the compounds are, the fingerprint is characteristic of material containing carbon-hydrogen bonds, and may include components like methyl and methylene.

Methyl means a carbon with at least 3 hydrogen bonded to it. Because carbon has 4 bonds, that 4th bond can be part of a chain, so a methyl group offers a very large body of molecules to choose from.

More info

Methlyene is a carbon with 2 hydrogen.

This article, which is a pretty good summary, says:

The organic molecules that have been detected on Ceres are complex aliphatic compounds that seem to be almost tar-like in nature.

Tar is a pretty nonspecific term, tar-like even more so, but tar is made by cooking coal or wood without oxygen, so I would assume this implies it's not Oxygen rich. More "simple" complex hydrocarbon chains (and because "simple" complex is somewhat confusing, another way to say that it's probably mostly Cs and Hs in a fairly big molecule, probably 5, maybe 6 carbons minimum I would think, otherwise it would be too quickly sublimated into gas. Tar like aliphatic compounds would still be vulnerable to photo-disintegration by UV light from the sun, which is common enough on Ceres Surface, but would be high enough melting points to not evaporate somewhat rapidly like shorter chains would. That these compounds were found locally probably implies somewhat recent, localized hydro-thermal activity.

The Aromatic C-H bond and the Aliphatic C-H bond have different spectroscopy. Source.

There is a weak alkene CH stretch above 3000 cm-1. This comes from the C-H bonds on carbons 1 and 2, the two carbons that are held together by the double bond. The strong CH stretch bands below 3000 cm-1 come from carbon-hydrogen bonds in the CH2 and CH3 groups.

and

The IR spectrum for benzene, C6H6, has only four prominent bands because it is a very symmetric molecule. Every carbon has a single bond to a hydrogen. Each carbon is bonded to two other carbons and the carbon-carbon bonds are alike for all six carbons. The molecule is planar. The aromatic CH stretch appears at 3100-3000 cm-1 There are aromatic CC stretch bands (for the carbon-carbon bonds in the aromatic ring) at about 1500 cm-1. Two bands are caused by bending motions involving carbon-hydrogen bonds.

So, less than 3,000 cm wavelength implies what the LA-Times article said, Methyl and Methylene or CH3 and CH2 groups on fairly long chain carbon molecules, probably tar-like. But that's hundreds, perhaps thousands of molecules that fit those criteria, some with single bonds between carbons, some with double bonds, some maybe more complex and from all the articles I've read, they don't know which ones. They can't tell which hydrocarbons by orbiting spectroscopy, they can only see the signature of the CH3 and/or CH2 groups at the end of the chains.

To know which molecules, they'll need to test a sample. So, a mars-like rover is probably going to go to Ceres at some point.

Why this is interesting is that these molecules aren't that long lived on the surface of Ceres, because UV light form the sun destroys them and they're location implies they came from inside Ceres, probably by hydro-thermal activity. There's also ammonia rich clay and carbonate rich clay and those are 3 key ingredients to life. None of this is proof that there's life underground in Ceres, but the ingredients are all there (or mostly there). Warm water (below the surface - and Ceres has a lot of internal water based on it's density), and the basic building blocks. It's still a far cry from proof of life as nothing has been found on the surface of Ceres that doesn't exist in comets, other than the implication of underground liquid water. But having all the ingredients in the same place is interesting.

Small point to add, but the article above mention Ammoniated Clay and Carbonates. Both of those are building blocks. Neither is organic.

This is strengthened by the fact that the molecules are found together with carbonates and clays containing ammonia. These have been observed in many regions of Ceres

Carbonates are simple. A molecule or molecules bound to a CO3(2-) is a carbonate.

Ammoniated clay took some looking up, but I found this:

The orbiting Dawn spacecraft has a more ideal perch to observe how molecules on the dwarf planet's surface reflect various wavelengths of light. It was in those wavelengths that Dawn investigator Carle Pieters and her colleagues spied the signature of ammoniated phyllosilicates, which are minerals similar to clays on Earth, mixed in with other materials.

Phyllosilicates are just clay or dissolved rock, with one or more OH- molecules. Ammoniated Phylosilicates, instead of having an OH- (Hydroxy group) have one or more NH2- (amides) or perhaps NH4+ (ammonium), which is a different charge so that wouldn't replace the OH but might still bond with silicates with hydro-thermal mixing.

From this article.

The researchers also identified a mixture of minerals on the surface of Ceres, which they think are ammonia-bearing clay minerals and magnesium carbonate. The clay minerals could have been produced by silicates reacting with ammonia ice. However, if Ceres had formed where it is now, it would not have been able to pick up any ammonia ice to enable such a reaction

Ceres ammonia clay implies ammonia rich waters under it's surface, so Ceres may have formed further away from the sun than it's current position, perhaps in the Kuipebelt where ammonia ice can exist and be part of a planet or moon's formation. Ceres lower density than most asteroid belt objects is also evidence of that. While it's important that Ceres has abundant ammonia, where it formed isn't relevant to this question.

Somewhat complex Chemistry happening inside a planet with heat, pressure and liquid water isn't surprising. None of these discoveries are even close to proof that Ceres has life, but they indicate that Ceres has all the basic building blocks of life. Bound Ammonia, hydrocarbons, carbonates and liquid water. It's still a huge step from building blocks to life, but these ingredients suggest it's worth taking a closer look.

Corrections are welcome. That's all I could deduce from reading the articles.


Dawn discovers evidence for organic material on Ceres (Update)

SwRI scientists are studying the geology associated with the organic-rich areas on Ceres. Dawn spacecraft data show a region around the Ernutet crater where organic concentrations have been discovered (labeled “a” through “f”). The color coding shows the strength of the organics absorption band, with warmer colors indicating the highest concentrations. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF/MPS/DLR/IDA

NASA's Dawn mission has found evidence for organic material on Ceres, a dwarf planet and the largest body in the main asteroid belt between Mars and Jupiter. Scientists using the spacecraft's visible and infrared mapping spectrometer (VIR) detected the material in and around a northern-hemisphere crater called Ernutet. Organic molecules are interesting to scientists because they are necessary, though not sufficient, components of life on Earth.

The discovery adds to the growing list of bodies in the solar system where organics have been found. Organic compounds have been found in certain meteorites as well as inferred from telescopic observations of several asteroids. Ceres shares many commonalities with meteorites rich in water and organics—in particular, a meteorite group called carbonaceous chondrites. This discovery further strengthens the connection between Ceres, these meteorites and their parent bodies.

"This is the first clear detection of organic molecules from orbit on a main belt body," said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome. The discovery is reported in the journal Science.

Data presented in the Science paper support the idea that the organic materials are native to Ceres. The carbonates and clays previously identified on Ceres provide evidence for chemical activity in the presence of water and heat. This raises the possibility that the organics were similarly processed in a warm water-rich environment.

This enhanced color composite image, made with data from the framing camera aboard NASA's Dawn spacecraft, shows the area around Ernutet Crater. The bright red portions appear redder with respect to the rest of Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Significance of organics

The organics discovery adds to Ceres' attributes associated with ingredients and conditions for life in the distant past. Previous studies have found hydrated minerals, carbonates, water ice, and ammoniated clays that must have been altered by water. Salts and sodium carbonate, such as those found in the bright areas of Occator Crater, are also thought to have been carried to the surface by liquid.

"This discovery adds to our understanding of the possible origins of water and organics on Earth," said Julie Castillo-Rogez, Dawn project scientist based at NASA's Jet Propulsion Laboratory in Pasadena, California.

Where are the organics?

The VIR instrument was able to detect and map the locations of this material because of its special signature in near-infrared light.

This enhanced color composite image from Dawn's visible and infrared mapping spectrometer shows the area around Ernutet Crater on Ceres. Credit: NASA/JPL-Caltech/UCLA/ASI/INAF

The organic materials on Ceres are mainly located in an area covering approximately 400 square miles (about 1,000 square kilometers). The signature of organics is very clear on the floor of Ernutet Crater, on its southern rim and in an area just outside the crater to the southwest. Another large area with well-defined signatures is found across the northwest part of the crater rim and ejecta. There are other smaller organic-rich areas several miles (kilometers) west and east of the crater. Organics also were found in a very small area in Inamahari Crater, about 250 miles (400 kilometers) away from Ernutet.

In enhanced visible color images from Dawn's framing camera, the organic material is associated with areas that appear redder with respect to the rest of Ceres. The distinct nature of these regions stands out even in low-resolution image data from the visible and infrared mapping spectrometer.

"We're still working on understanding the geological context for these materials," said study co-author Carle Pieters, professor of geological sciences at Brown University, Providence, Rhode Island.

Having completed nearly two years of observations in orbit at Ceres, Dawn is now in a highly elliptical orbit at Ceres, going from an altitude of 4,670 miles (7,520 kilometers) up to almost 5,810 miles (9,350 kilometers). On Feb. 23, it will make its way to a new altitude of around 12,400 miles (20,000 kilometers), about the height of GPS satellites above Earth, and to a different orbital plane. This will put Dawn in a position to study Ceres in a new geometry. In late spring, Dawn will view Ceres with the sun directly behind the spacecraft, such that Ceres will appear brighter than before, and perhaps reveal more clues about its nature.


Astronomers Discover Evidence for Organic Material on Ceres

This enhanced color composite image, made with data from the framing camera aboard NASA’s Dawn spacecraft, shows the area around Ernutet Crater. The bright red portions appear redder with respect to the rest of Ceres.

Using data from NASA’s Dawn Mission, a team of astronomers has discovered evidence for organic material on dwarf planet Ceres.

NASA’s Dawn mission has found evidence for organic material on Ceres, a dwarf planet and the largest body in the main asteroid belt between Mars and Jupiter. Scientists using the spacecraft’s visible and infrared mapping spectrometer (VIR) detected the material in and around a northern-hemisphere crater called Ernutet. Organic molecules are interesting to scientists because they are necessary, though not sufficient, components of life on Earth.

The discovery adds to the growing list of bodies in the solar system where organics have been found. Organic compounds have been found in certain meteorites as well as inferred from telescopic observations of several asteroids. Ceres shares many commonalities with meteorites rich in water and organics — in particular, a meteorite group called carbonaceous chondrites. This discovery further strengthens the connection between Ceres, these meteorites and their parent bodies.

“This is the first clear detection of organic molecules from orbit on a main belt body,” said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome. The discovery is reported in the journal Science.

Data presented in the Science paper support the idea that the organic materials are native to Ceres. The carbonates and clays previously identified on Ceres provide evidence for chemical activity in the presence of water and heat. This raises the possibility that the organics were similarly processed in a warm water-rich environment.

This enhanced color composite image from Dawn’s visible and infrared mapping spectrometer shows the area around Ernutet Crater on Ceres. The instrument detected the evidence of organic materials in this area, as reported in a 2017 study in the journal Science. In this view, areas that appear pink with respect to the background appear to be rich in organics, and green areas are where organic material appears to be less abundant.Light with a wavelength of 2000 nanometers is shown in blue, 3400 nanometers is shown in green and 1700 nanometers is shown in red.

Significance of organics

The organics discovery adds to Ceres’ attributes associated with ingredients and conditions for life in the distant past. Previous studies have found hydrated minerals, carbonates, water ice, and ammoniated clays that must have been altered by water. Salts and sodium carbonate, such as those found in the bright areas of Occator Crater, are also thought to have been carried to the surface by liquid.

“This discovery adds to our understanding of the possible origins of water and organics on Earth,” said Julie Castillo-Rogez, Dawn project scientist based at NASA’s Jet Propulsion Laboratory in Pasadena, California.

Where are the organics?

The VIR instrument was able to detect and map the locations of this material because of its special signature in near-infrared light.

The organic materials on Ceres are mainly located in an area covering approximately 400 square miles (about 1,000 square kilometers). The signature of organics is very clear on the floor of Ernutet Crater, on its southern rim and in an area just outside the crater to the southwest. Another large area with well-defined signatures is found across the northwest part of the crater rim and ejecta. There are other smaller organic-rich areas several miles (kilometers) west and east of the crater. Organics also were found in a very small area in Inamahari Crater, about 250 miles (400 kilometers) away from Ernutet.

In enhanced visible color images from Dawn’s framing camera, the organic material is associated with areas that appear redder with respect to the rest of Ceres. The distinct nature of these regions stands out even in low-resolution image data from the visible and infrared mapping spectrometer.

“We’re still working on understanding the geological context for these materials,” said study co-author Carle Pieters, professor of geological sciences at Brown University, Providence, Rhode Island.

Ernutet Crater measures about 32 miles (52 kilometers) in diameter and is located in the northern hemisphere of Ceres.

Next steps for Dawn

Having completed nearly two years of observations in orbit at Ceres, Dawn is now in a highly elliptical orbit at Ceres, going from an altitude of 4,670 miles (7,520 kilometers) up to almost 5,810 miles (9,350 kilometers). On Feb. 23, it will make its way to a new altitude of around 12,400 miles (20,000 kilometers), about the height of GPS satellites above Earth, and to a different orbital plane. This will put Dawn in a position to study Ceres in a new geometry. In late spring, Dawn will view Ceres with the sun directly behind the spacecraft, such that Ceres will appear brighter than before, and perhaps reveal more clues about its nature.


Building blocks of life

"The discovery indicates that the starting material in the solar system contained the essential elements, or the building blocks, for life," Russell said.

"Ceres may have been able to take this process only so far. Perhaps to move further along the path took a larger body with more complex structure and dynamics," like Earth, Russell added.

The organic material was found near a 50-kilometre-wide crater in Ceres' northern hemisphere. Although the exact molecular compounds in the organics could not be identified, they matched tar-like minerals, such as kerite or asphaltite, the scientists wrote.

"Because Ceres is a dwarf planet that may still preserve internal heat from its formation period and may even contain a subsurface ocean, this opens the possibility that primitive life could have developed on Ceres itself," planetary scientist Michael Kuppers of the European Space Astronomy Centre in Madrid wrote in a related essay in the journal Science.

Based on the location and type of organics found on Ceres, scientists ruled out the possibility they were deposited by a crashing asteroid or comet.

Lead researcher Maria Cristina De Sanctis of Italy's National Institute for Astrophysics and colleagues suspect the material formed inside Ceres through hydrothermal activity, though how the organics reached the surface remains a mystery.


3 Methods

VIR image cubes from both the high-altitude mapping orbit (HAMO, n = 20) and low-altitude mapping orbit (LAMO, n = 15) mission phases were calibrated, thermally corrected, and spectrally filtered for a spatial area of

650 × 650 km centered on Ernutet crater (supporting information Table S3, supplementary section for full image processing description). A band depth map for aliphatic C–H (3.42 μm) was produced using a linear continuum removal method (e.g., Clark & Roush, 1984 ) with tie points at 3.20 and 3.60 μm. Spectra were averaged over regions of interest (ROIs) consisting of

30–180 pixels that were commonly (but not always) contiguous, on average covering an area of

15 km 2 . These ROIs were chosen from a subset of images to cover at least one organic-rich region.

Reflectance spectra of isolated kerogens extracted from terrestrial sedimentary rocks and IOM extracted from carbonaceous chondrite meteorites were measured from 0.3 to 25 μm for samples with previously reported elemental abundances (Alexander et al., 2007 , 2010 Kaplan & Milliken, 2018 Schopf, 1983 and full description in Table S1). C chondrite spectra (n = 64) from the Reflectance Experiment LABoratory database were reanalyzed for this study by calculating band depth at 3.42 μm. Laboratory and VIR spectra were resampled to the same wavelengths and converted to single scattering albedo (SSA) via the model of Hapke ( 1993 see the supporting information for full description).

Once converted to SSA, which minimizes effects due to multiple scattering, each Ceres spectrum was modeled as a mixture between two endmembers: Ceres's average spectrum and a laboratory organic spectrum. The average Ceres spectrum was obtained from the regional HAMO and LAMO image data set (two images from each data set that contained the bulk of the organic spectral signatures were not included in the spectral average). A nonnegative least squares solution was found between a linear combination of the two spectral endmembers and the observed Ceres SSA spectrum over the 1.5 to 4.08 μm wavelength range. Additional endmembers, including a flat line and lines with ±1 slopes, were included to account for albedo and slope differences between the Ceres spectra. The organic spectral fraction was calculated by normalizing the regression coefficients of the organic endmember. Eight different organic endmembers were tested in the spectral model to determine the effects of organic composition on modeled organic spectral fractions (Table S2). These least squares fits were performed on the average spectra for the ROIs, as well as each spectrum (pixel) in individual HAMO and LAMO images, where the latter result in maps of organic spectral abundance that can be compared to local surface morphology. Additional details on VIR data processing and modeling are provided in the supporting information.


Contents

Discovery Edit

Johann Elert Bode, in 1772, first suggested that an undiscovered planet could exist between the orbits of Mars and Jupiter. [27] Kepler had already noticed the gap between Mars and Jupiter in 1596. [27] Bode based his idea on the Titius–Bode law which is a now-discredited hypothesis that was first proposed in 1766. Bode observed that there was a regular pattern in the size of the orbits of known planets, and that the pattern was marred only by the large gap between Mars and Jupiter. [27] [28] The pattern predicted that the missing planet ought to have an orbit with a radius near 2.8 astronomical units (AU). [28] William Herschel's discovery of Uranus in 1781 [27] near the predicted distance for the next body beyond Saturn increased faith in the law of Titius and Bode, and in 1800, a group headed by Franz Xaver von Zach, editor of the Monatliche Correspondenz, sent requests to twenty-four experienced astronomers (whom he dubbed the "celestial police"), asking that they combine their efforts and begin a methodical search for the expected planet. [27] [28] Although they did not discover Ceres, they later found several large asteroids. [28]

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. [29] [30] He was searching for "the 87th [star] of the Catalogue of the Zodiacal stars of Mr la Caille", but found that "it was preceded by another". [27] Instead of a star, Piazzi had found a moving star-like object, which he first thought was a comet. [31] Piazzi observed Ceres a total of 24 times, the final time on 11 February 1801, when illness interrupted his observations. He announced his discovery on 24 January 1801 in letters to only two fellow astronomers, his compatriot Barnaba Oriani of Milan and Johann Elert Bode of Berlin. [32] 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". [27] In April, Piazzi sent his complete observations to Oriani, Bode, and Jérôme Lalande in Paris. The information was published in the September 1801 issue of the Monatliche Correspondenz. [31]

By this time, the apparent position of Ceres had changed (mostly due to Earth's orbital motion), and was too close to the Sun's glare for other astronomers to confirm Piazzi's observations. Toward 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, Carl Friedrich Gauss, then 24 years old, developed an efficient method of orbit determination. [31] In a few weeks, he predicted the path of Ceres and sent his results to von Zach. On 31 December 1801, von Zach and Heinrich W. M. Olbers found Ceres near the predicted position and thus recovered it. [31]

The early observers were only able to calculate the size of Ceres to within an order of magnitude. Herschel underestimated its diameter as 260 km in 1802, whereas in 1811 Johann Hieronymus Schröter overestimated it as 2,613 km. [33] [34]

Name Edit

Piazzi's initial name for his discovery was Cerere Ferdinandea. Cerere was the Italian name of Ceres, the Roman goddess of agriculture, whose earthly home, and oldest temple, lay in Sicily. "Ferdinandea" was in honor of Piazzi's concurrent monarch and patron, King Ferdinand of Sicily. [27] [31] "Ferdinandea", however, was not acceptable to other nations and was dropped. Prior to Von Zach's confirmation in December 1801, he referred to the planet as Hera, while Bode preferred Juno. Despite Piazzi's objections, these two names gained currency in Germany before the world's existence was confirmed. Once it was, astronomers settled on Piazzi's name of "Ceres". [35] Cerium, a rare-earth element discovered in 1803, was named after Ceres. [36] [c] In the same year, another element was also initially named after Ceres, but, when cerium was named, its discoverer changed the latter to palladium, after the second asteroid, 2 Pallas. [38]

The regular adjectival forms of the name are Cererian [39] [40] / s ɪ ˈ r ɪər i ə n / [41] and Cererean [42] (with the same pronunciation), [43] both derived from the Latin oblique stem Cĕrĕr-. [44] The irregular form Ceresian / s ɪ ˈ r iː z i ə n / is occasionally seen for the goddess (as in the sickle-shaped Ceresian Lake), as are, by analogy with cereal, the forms Cerean / ˈ s ɪər i ə n / [45] and Cerealian / s ɛr i ˈ eɪ l i ə n / . [46] The old astronomical symbol of Ceres is a sickle, ⟨⚳⟩, [47] similar to Venus' symbol ⟨♀⟩ but with a break in the circle. It has a variant ⟨⚳⟩ , reversed under the influence of the initial letter 'C' of 'Ceres'. These symbols were later replaced with the generic asteroid symbol of a numbered disk, ⟨①⟩. [31] [48]

Classification Edit

The categorization of Ceres has changed more than once and has been the subject of some disagreement. Johann Elert Bode believed Ceres to be the "missing planet" he had proposed to exist between Mars and Jupiter, at a distance of 419 million km (2.8 AU) from the Sun. [27] Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables (along with 2 Pallas, 3 Juno, and 4 Vesta) for half a century. [27] [31] [49]

As other objects were discovered in the neighborhood of Ceres, it was realized that Ceres represented the first of a new class of objects. [27] In 1802, with the discovery of 2 Pallas, William Herschel coined the term asteroid ("star-like") for these bodies, [49] writing that "they resemble small stars so much as hardly to be distinguished from them, even by very good telescopes". [50] As the first such body to be discovered, Ceres was given the designation 1 Ceres under the modern system of minor-planet designations. By the 1860s, the existence of a fundamental difference between asteroids such as Ceres and the major planets was widely accepted, though a precise definition of "planet" was never formulated. [49]

The 2006 debate surrounding Pluto and what constitutes a planet led to Ceres being considered for reclassification as a planet. [51] [52] A proposal before the International Astronomical Union for the definition of a planet would have 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". [53] Had this resolution been adopted, it would have made Ceres the fifth planet in order from the Sun. [54] This never happened, however, and on 24 August 2006 a modified definition was adopted, carrying the additional requirement that a planet must have "cleared the neighborhood around its orbit". By this definition, 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 25% of the belt's total mass. [55] Bodies that met the first proposed definition but not the second, such as Ceres, were instead classified as dwarf planets.

Ceres is the largest asteroid in the Main Belt. [12] It has sometimes been assumed that Ceres was reclassified as a dwarf planet, and that it is therefore no longer considered an asteroid. For example, a news update at Space.com spoke of "Pallas, the largest asteroid, and Ceres, the dwarf planet formerly classified as an asteroid", [56] whereas an IAU question-and-answer posting states, "Ceres is (or now we can say it was) the largest asteroid", though it then speaks of "other asteroids" crossing Ceres' path and otherwise implies that Ceres is still considered an asteroid. [57] The Gazetteer of Planetary Nomenclature at the IAU lists Ceres under 'Asteroids'. [58] The Minor Planet Center notes that such bodies may have dual designations. [59] The 2006 IAU decision that classified Ceres as a dwarf planet also implied that it is simultaneously an asteroid. It introduces the category of small Solar System body, as objects that are neither planets nor dwarf planets, and states that they 'currently include most of the Solar System asteroids'. The only object among the asteroids that would prevent all asteroids from being SSSBs is Ceres. Lang (2011) comments "the [IAU has] added a new designation to Ceres, classifying it as a dwarf planet. . By [its] definition, Eris, Haumea, Makemake and Pluto, as well as the largest asteroid, 1 Ceres, are all dwarf planets", and describes it elsewhere as "the dwarf planet–asteroid 1 Ceres". [60] NASA refers to Ceres as a dwarf planet, [61] as do various academic textbooks. [62] [63] However, NASA has at least once referred to Vesta as the largest asteroid. [64]

Ceres follows an orbit between Mars and Jupiter, within the asteroid belt and closer to the orbit of Mars, with a period of 4.6 Earth years. [3] The orbit is moderately inclined (i = 10.6° compared to 7° for Mercury and 17° for Pluto) and moderately eccentric (e = 0.08 compared to 0.09 for Mars). [3]

The diagram illustrates the orbits of Ceres (blue) and several planets (white and gray). The segments of orbits below the ecliptic are plotted in darker colors, and the orange plus sign is the Sun's location. The top left diagram is a polar view that shows the location of Ceres in the gap between Mars and Jupiter. The top right is a close-up demonstrating the locations of the perihelia (q) and aphelia (Q) of Ceres and Mars. In this diagram (but not in general), the perihelion of Mars is on the opposite side of the Sun from those of Ceres and several of the large main-belt asteroids, including 2 Pallas and 10 Hygiea. The bottom diagram is a side view showing the inclination of the orbit of Ceres compared to the orbits of Mars and Jupiter.

Ceres was once thought to be a member of an asteroid family. [65] The asteroids of this family share similar proper orbital elements, which may indicate a common origin through an asteroid collision some time in the past. Ceres was later found to have spectral properties different from other members of the family, which is now called the Gefion family after the next-lowest-numbered family member, 1272 Gefion. [65] Ceres appears to be merely an interloper in the Gefion family, coincidentally having similar orbital elements but not a common origin. [66]

Resonances Edit

Ceres is in a near-1:1 mean-motion orbital resonance with Pallas (their proper orbital periods differ by 0.2%). [67] However, a true resonance between the two would be unlikely due to their small masses relative to their large separations, such relationships among asteroids are very rare. [68] Nevertheless, Ceres is able to capture other asteroids into temporary 1:1 resonant orbital relationships (making them temporary trojans) for periods up to 2 million years or more fifty such objects have been identified. [69]

Proper (long-term mean) orbital elements compared to osculating (instant) orbital elements for Ceres:
Element
type
a
(in AU)
e i Period
(in days)
Proper [4] 2.7671 0.116198 9.647435 1,681.60
Osculating [3]
(Epoch 23 July 2010 )
2.7653 0.079138 10.586821 1,679.66
Difference 0.0018 0.03706 0.939386 1.94

Transits of planets from Ceres Edit

Mercury, Venus, Earth, and Mars can all appear to cross the Sun, or transit it, from a vantage point on Ceres. The most common transits are those of Mercury, which usually happen every few years, most recently in 2006 and 2010. The most recent transit of Venus was in 1953, and the next will be in 2051 the corresponding dates are 1814 and 2081 for transits of Earth, and 767 and 2684 for transits of Mars. [70]

The rotation period of Ceres (the Cererian day) is 9 hours and 4 minutes. It has an axial tilt of 4°. [9] This is small enough for Ceres's polar regions to contain permanently shadowed craters that are expected to act as cold traps and accumulate water ice over time, similar to the situation 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 3 times before escaping or being trapped. [9]

Hubble observations indicated that the north pole of Ceres pointed in the direction of right ascension 19 h 24 min (291°), declination +59°, in the constellation Draco, resulting in an axial tilt of approximately 3°. [11] Dawn later determined that the north polar axis actually 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°. [71]

Over the course of 3 million years, gravitational influence from Jupiter and Saturn has triggered cyclical shifts in Ceres's axial tilt, ranging from 2 to 20 degrees, meaning that seasonal effects have occurred in the past, with the most recent 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 their water over the age of the Solar System. [72]

Ceres has a mass of 9.39 × 10 20 kg as determined from the Dawn spacecraft. [73] With this mass Ceres composes approximately a quarter of the estimated total 3.0 ± 0.2 × 10 21 kg mass of the asteroid belt, [55] or 1.3% of the mass of the Moon. Ceres is close to being in hydrostatic equilibrium, and thus to being a dwarf planet. However, there are some deviations from an equilibrium shape that have yet to be fully explained. [19] Among Solar System bodies, Ceres is intermediate in size between the smaller asteroid Vesta and the larger moon Tethys, and approximately the size of the large trans-Neptunian object Orcus. Its surface area is approximately the same as the land area of India or Argentina. [74] In July 2018, NASA released a comparison of physical features found on Ceres with similar ones present on Earth. [75]

Ceres is the smallest object likely to be in hydrostatic equilibrium, being 600 km smaller and less than half the mass of Saturn's moon Rhea, the next smallest likely (but unproven) object. [76] Modeling has suggested Ceres could have a small metallic core from partial differentiation of its rocky fraction, [77] [78] but the data are consistent with a mantle of hydrated silicates and no core. [19]

Surface Edit

The surface of Ceres is "remarkably" homogeneous on a global scale, and is rich in carbonates and ammoniated phyllosilicates that have been altered by water. [19] However, water ice in the regolith varies from approximately 10% in polar latitudes to much drier, even ice-free, in the equatorial regions. [15] [19] Another large-scale variation is found in three large shallow basins (planitia) with degraded rims these may be cryptic craters, and two of the three have higher than average ammonium concentrations. [19]

The water ocean that is thought to have existed early in Ceres's history 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. [19]

Studies by the Hubble Space Telescope reveal that graphite, sulfur, and sulfur dioxide are present on Ceres's surface. The former 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 are evidently associated with areas with recent geological activity. [79]

Craters Edit

Prior to the Dawn mission, only a few surface features had been unambiguously detected on Ceres. High-resolution ultraviolet Hubble Space Telescope images taken in 1995 showed a dark spot on its surface, which was nicknamed "Piazzi" in honor of the discoverer of Ceres. [21] This was thought to be a crater. Later near-infrared images with a higher resolution taken over a whole rotation with the Keck telescope using adaptive optics showed several bright and dark features moving with Ceres' rotation. [80] [81] Two dark features had circular shapes and were presumed to be craters one of them was observed to have a bright central region, whereas another was identified as the "Piazzi" feature. [80] [81] Visible-light Hubble Space Telescope images of a full rotation taken in 2003 and 2004 showed eleven recognizable surface features, the natures of which were then undetermined. [11] [82] One of these features corresponds to the "Piazzi" feature observed earlier. [11] Dawn revealed that Ceres has a heavily cratered surface nevertheless, Ceres does not have as many large craters as expected, likely due to past geological processes. [83] [84]

Cryovolcanism Edit

Ceres has one prominent mountain, Ahuna Mons this peak appears to be a cryovolcano and has few craters, suggesting a maximum age of no more than a few hundred million years. [86] [87] Its relatively high gravitational field suggests it is very 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. [88]

A later computer simulation has suggested that there were originally as many as 22 cryovolcanoes on Ceres that are now unrecognisable due to viscous relaxation. [89] Models suggest that one cryovolcano should form on Ceres every 50 million years. [90]

An unexpectedly large number of Cererian craters have central pits, perhaps due to cryovolcanic processes, and many have central peaks. [91] Several bright spots (faculae) have been observed by Dawn, the brightest spot ("Spot 5") located in the middle of an 80-kilometer (50 mi) crater called Occator. [92] From images taken of Ceres on 4 May 2015, the secondary bright spot was revealed to actually be a group of scattered bright areas, possibly as many as ten. These bright features have an albedo of approximately 40% [93] that are caused by a substance on the surface, possibly ice or salts, reflecting sunlight. [94] [95] The spot in the center of the crater is named Cerealia Facula, [96] and the group of spots to the east - Vinalia Faculae. [97] A haze periodically appears above Spot 5, the best known bright spot, supporting the hypothesis that some sort of outgassing or sublimating ice formed the bright spots. [95] [98] In March 2016, Dawn found definitive evidence of water molecules on the surface of Ceres at Oxo crater. [99] [100]

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 hexahydrite (MgSO4·6H2O) the spots were also found to be associated with ammonia-rich clays. [101] 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 ). [102] [103] These materials have been suggested to originate from the recent crystallization of brines that reached the surface from below. [104] [105] [106] [107] [108] In August 2020, NASA confirmed that Ceres was a water-rich body with a deep reservoir of brine that percolated to the surface in various locations causing "bright spots", including those in Occator crater. [109] [110]

Carbon Edit

Organic compounds (tholins) were detected on Ceres in Ernutet crater, [111] [112] and most of the planet's surface is extremely rich in carbon, [113] with approximately 20% carbon by mass in its near surface. [114] [115] The carbon content is more than five times higher than in carbonaceous chondrite meteorites analyzed on Earth. [115] The surface carbon shows evidence of being mixed with products of rock-water interactions, such as clays. [114] [115] 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 favorable to organic chemistry. [114] [115] Its presence on Ceres is evidence that the basic ingredients for life can be found throughout the universe. [113]

Boulders Edit

There are 4423 boulders larger than 105 meters on the surface of Ceres. These boulders are found within or near craters, though not all craters contain boulders. Vast regions of the surface of Ceres don't have any large (> 100 m) boulders. In addition, the large boulders on Ceres are more numerous at higher latitudes than at lower latitudes. These boulders are very brittle and degrade rapidly due to thermal stress (at dawn and dusk, the surface temperature changes rapidly) and meteoritic impacts. Their maximum age is of 150 million years, which is much shorter than the lifetime of boulders on Vesta. [116]

Internal structure Edit

The active geology of Ceres is driven by ice and brines, with an overall salinity of around 5%. Altogether, Ceres is approximately 40% or 50% water by volume, compared to 0.1% for Earth, and 73% rock by weight. [15]

The fact that the surface has preserved craters smaller than 300 km in diameter indicate that the outermost layer of Ceres is on the order of 1000 times stronger than water ice. This is consistent with a mixture of silicates, hydrated salts and methane clathrates, with no more than approximately 30% water ice. [19]

The thickness and density of the crust is not well constrained. There are competing 2-layer and 3-layer models of the Cererian interior, not counting a possible small metallic core.

Three-layer model Edit

In the three-layer model, Ceres is thought to consist of an inner muddy mantle of hydrated rock, such as clays, an intermediate layer of brine and rock (mud) down to a depth of at least 100 km, and an outer, 40-km thick crust of ice, salts and hydrated minerals. [117] It's unknown if it contains a rocky or metallic core, but the low central density suggests it may retain about 10% porosity. [15] One study estimated the densities of the core and mantle/crust to be 2.46–2.90 and 1.68–1.95 g/cm 3 , with the mantle and crust being 70–190 km thick. Only partial dehydration (expulsion of ice) from the core is expected, while the high density of the mantle relative to water ice reflects its enrichment in silicates and salts. [8] That is, the core, mantle and crust all consist of rock and ice, though in different ratios.

The mineral composition can only be determined indirectly for the outer 100 km. The 40-km thick solid outer crust 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 limit of detection. Under that is thought to be a mantle dominated by hydrated rocks such as clays. It is not possible to tell if Ceres' deep interior contains liquid or a core of dense material rich in metal. [118]

Two-layer model Edit

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 20 meters thick. There are range to the extent of differentiation that is consistent with the data, from a large, 360-km core of 75% chondrules and 25% particulates and a mantle of 75% ice and 25% particulates, to a small, 85-km 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. In the latter case, a 2% freezing of the liquid reservoir would compress the liquid enough to force some to the surface, producing cryovolcanism. [119]

Another model notes that Dawn data is consistent with 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 3 ), the crust would be approximately 70 km thick and have a density of 1.68 g/cm 3 with CM-class meteorites (density 2.9 g/cm 3 ), the crust would be approximately 190 km thick and have a density of 1.9 g/cm 3 . Best-fit from admittance modeling yields a crust approximately 40 km thick with a density of approximately 1.25 g/cm 3 , and a mantle/core density of approximately 2.4 g/cm 3 . [19]

There are indications that Ceres has a tenuous water vapor atmosphere outgassing from water ice on the surface, making it an active asteroid. [120] [121] [122] [123]

Surface water ice is unstable at distances less than 5 AU from the Sun, [124] so it is expected to sublime if it is exposed directly to solar radiation. Water ice can migrate from the deep layers of Ceres to the surface, but escapes in a very short time.

In early 2014, using data from the Herschel Space Observatory, it was discovered that there are several localized (not more than 60 km in diameter) mid-latitude sources of water vapor on Ceres, which each give off approximately 10 26 molecules (or 3 kg) of water per second. [125] [126] [d] Two potential source regions, designated Piazzi (123°E, 21°N) and Region A (231°E, 23°N), have been visualized in the near infrared as dark areas (Region A also has a bright center) by the W. M. Keck Observatory. Possible mechanisms for the vapor release are sublimation from approximately 0.6 km 2 of exposed surface ice, or cryovolcanic eruptions resulting from radiogenic internal heat [125] or from pressurization of a subsurface ocean due to growth of an overlying layer of ice. [129] Surface sublimation would be expected to be lower when Ceres is farther from the Sun in its orbit, whereas internally powered emissions should not be affected by its orbital position. The limited data available was more consistent with cometary-style sublimation [125] however, subsequent evidence from Dawn strongly suggests ongoing geologic activity could be at least partially responsible. [130] [131]

Studies using Dawn's gamma ray and neutron detector (GRaND) reveal that Ceres is accelerating electrons from the solar wind regularly although there are several possibilities as to what is causing this, the most accepted is that these electrons are being accelerated by collisions between the solar wind and a tenuous water vapor exosphere. [132]

In 2017, Dawn confirmed that Ceres has a transient atmosphere that appears to be linked to solar activity. Ice on Ceres can sublimate when energetic particles from the Sun hit exposed ice within craters. [133]

Ceres is a surviving protoplanet (planetary embryo) that formed 4.56 billion years ago, the only one surviving in the inner Solar System, with the rest either merging to form terrestrial planets or being ejected from the Solar System by Jupiter. [134] However, its composition is not consistent with a formation in the asteroid belt. It seems rather that Ceres formed as a centaur, most likely between the orbits of Jupiter and Saturn, and was scattered into the asteroid belt as Jupiter migrated outward. [15] The discovery of ammonia salts in Occator crater supports an origin in the outer Solar System. [135] However, the presence of ammonia ices can be attributed to impacts by comets, and ammonia salts are more likely to be native to the surface. [136]

The geological evolution of Ceres was dependent on the heat sources available during and after its formation: friction from planetesimal accretion, and decay of various radionuclides (possibly including short-lived extinct radionuclides such as aluminium-26). These are thought to have been sufficient to allow Ceres to differentiate into a rocky core and icy mantle soon after its formation. [78] Ceres possesses a surprisingly small number of large craters, suggesting that viscous relaxation, water volcanism and tectonics may have erased older geological features. [137] Ceres's relatively warm surface temperature implies that any of the resulting ice on its surface would have gradually sublimated, leaving behind various hydrated minerals like clay minerals and carbonates. [88]

Today, Ceres has become considerably less geologically active, with a surface sculpted chiefly by impacts nevertheless, evidence from Dawn reveals that internal processes have continued to sculpt Ceres's surface to a significant extent, in stark contrast to Vesta [138] and of previous expectations that Ceres would have become geologically dead early in its history due to its small size. [139] There are significant amounts of water ice in its crust. [112]

Although Ceres is not as actively discussed as a potential home for microbial extraterrestrial life as Mars, Europa, Enceladus, or Titan, it is the most water-rich body in the inner Solar System after Earth, [88] and there is evidence that its icy mantle was once a watery subterranean ocean. [115] Although it does not experience tidal heating, like Europa or Enceladus, it is close enough to the Sun, and contains enough long-lived radioactive isotopes, to preserve liquid water in its subsurface for extended periods. [88] The remote detection of organic compounds and the presence of water with 20% carbon by mass in its near surface could provide conditions favorable to organic chemistry. [114] [115] While Ceres is rich in carbon, hydrogen, oxygen and nitrogen, the two other crucial biogenic elements, sulfur and phosphorus, have proven elusive. [88] [140] The relaxation of Ceres' topgraphy across its surface is evidence for a liquid layer some 60 km below the surface, or at the very least, pockets of brine, that may persist to the present. [88]

Observation Edit

When in opposition near its perihelion, Ceres can reach an apparent magnitude of +6.7. [142] This is generally regarded as too dim to be visible to the naked eye, but under ideal viewing conditions, keen eyes with 20/20 vision may be able to see it. The only other asteroids that can reach a similarly bright magnitude are 4 Vesta and, when in rare oppositions near their perihelions, 2 Pallas and 7 Iris. [143] 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.

Some notable observations and milestones for Ceres include the following:

  • 1984 November 13: An occultation of a star by Ceres observed in Mexico, Florida and across the Caribbean. [144]
  • 1995 June 25: UltravioletHubble Space Telescope images with 50-kilometer resolution. [21][145]
  • 2002: Infrared images with 30-km resolution taken with the Keck telescope using adaptive optics. [81]
  • 2003 and 2004: Visible light images with 30-km resolution (the best prior to the Dawn mission) taken using Hubble. [11][82]
  • 2012 December 22: Ceres occulted the star TYC 1865-00446-1 over parts of Japan, Russia, and China. [146] Ceres' brightness was magnitude 6.9 and the star, 12.2. [146]
  • 2014: Ceres was found to have a tenuous atmosphere (exosphere) of water vapor, confirmed by the Herschel space telescope. [147]
  • 2015: The NASA Dawn spacecraft approached and orbited Ceres, sending detailed images and scientific data back to Earth.

Proposed exploration Edit

In 1981, a proposal for an asteroid mission was submitted to the European Space Agency (ESA). Named the Asteroidal Gravity Optical and Radar Analysis (AGORA), this spacecraft was to launch some time in 1990–1994 and perform two flybys of large asteroids. The preferred target for this mission was Vesta. AGORA would reach the asteroid belt either by a gravitational slingshot trajectory past Mars or by means of a small ion engine. However, the proposal was refused by ESA. A joint NASA–ESA asteroid mission was then drawn up for a Multiple Asteroid Orbiter with Solar Electric Propulsion (MAOSEP), with one of the mission profiles including an orbit of Vesta. NASA indicated they were not interested in an asteroid mission. Instead, ESA set up a technological study of a spacecraft with an ion drive. Other missions to the asteroid belt were proposed in the 1980s by France, Germany, Italy, and the United States, but none were approved. [148] Exploration of Ceres by fly-by and impacting penetrator was the second main target of the second plan of the multiaimed Soviet Vesta mission, developed in cooperation with European countries for realisation in 1991–1994 but canceled due to the Soviet Union disbanding.

The Chinese Space Agency is designing a sample-return mission from Ceres that would take place during the 2020s. [149]

The Calathus Mission is a concept to Occator Crater at Ceres, to return a sample of the bright carbonate faculae and dark organics to Earth. [150] [151]

Dawn mission Edit

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 recommended as a high priority a mission to explore the asteroid belt using a spacecraft with an ion engine. Funding for this program remained problematic for several years, but by 2004 the Dawn vehicle had passed its critical design review. [152]

It was launched on 27 September 2007, as the space mission to make the first visits to both Vesta and Ceres. On 3 May 2011, Dawn acquired its first targeting image 1.2 million kilometers from Vesta. [153] After orbiting Vesta for 13 months, Dawn used its ion engine to depart for Ceres, with gravitational capture occurring on 6 March 2015 [154] at a separation of 61,000 km, [155] four months prior to the New Horizons flyby of Pluto.

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 on 23 April 2015, staying for only approximately one orbit (fifteen days). [24] [156] The spacecraft subsequently reduced its orbital distance to 4,400 km for its second observational orbit ("survey") for three weeks, [157] then down to 1,470 km ("HAMO" high altitude mapping orbit) for two months [158] and then down to its final orbit at 375 km ("LAMO" low altitude mapping orbit) for at least three months. [159]

The spacecraft instrumentation includes a framing camera, a visual and infrared spectrometer, and a gamma-ray and neutron detector. These instruments examined Ceres' shape and elemental composition. [160] On 13 January 2015, Dawn took the first images of Ceres at near-Hubble resolution, revealing impact craters and a small high-albedo spot on the surface, near the same location as that observed previously. Additional imaging sessions, at increasingly better resolution took place on 25 January 4, 12, 19 and 25 February 1 March, and 10 and 15 April. [161]

Pictures with a resolution previously unattained were taken during imaging sessions starting in January 2015 as Dawn approached Ceres, showing a cratered surface. Two distinct bright spots (or high-albedo features) inside a crater (different from the bright spots observed in earlier Hubble images [162] ) were seen in a 19 February 2015 image, leading to speculation about a possible cryovolcanic origin [163] [164] [165] or outgassing. [166] On 3 March 2015, a NASA spokesperson said the spots are consistent with highly reflective materials containing ice or salts, but that cryovolcanism is unlikely. [167] However, on 2 September 2016, scientists from the Dawn team claimed in a Science paper that a massive cryovolcano called Ahuna Mons is the strongest evidence yet for the existence of these mysterious formations. [168] [169] On 11 May 2015, NASA released a higher-resolution image showing that, instead of one or two spots, there are actually several. [170] 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 hexahydrite (MgSO4·6H2O) the spots were also found to be associated with ammonia-rich clays. [101] 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. [104] [105] [107] In July 2018, NASA released a comparison of physical features found on Ceres with similar ones present on Earth. [75] From June to October 2018, Dawn orbited Ceres from as close as 35 km (22 mi) and as far away as 4,000 km (2,500 mi). [171] [172] The Dawn mission ended on 1 November 2018 after the spacecraft ran out of fuel.

In October 2015, NASA released a true-color portrait of Ceres made by Dawn. [173] In February 2017, organics (tholins) were detected on Ceres in Ernutet crater (see image). [111] [112]

Dawn 's arrival in a stable orbit around Ceres was delayed after, close to reaching Ceres, it was hit by a cosmic ray, making it take another, longer route around Ceres in back, instead of a direct spiral towards it. [174]

Map of Ceres (centered on 180° longitude color March 2015)

Map of Ceres (Mercator HAMO color March 2016)

Map of Ceres (Elliptical HAMO color March 2016)

Black-and-white photographic map of Ceres, centered on 180° longitude, with official nomenclature (September 2017)

Topographic map of Ceres (September 2016).
15 km (10 mi) of elevation separate the lowest crater floors (indigo) from the highest peaks (white). [175]

Hemispheric topographic maps of Ceres, centered on 60° and 240° east longitude (July 2015).

Ceres, polar regions (November 2015): North (left) south (right).

Map of quadrangles Edit

The following imagemap of Ceres is divided into 15 quadrangles. They are named after the first craters whose names the IAU approved in July 2015. [176] The map image(s) were taken by the Dawn space probe.


NASA Reveals New Clues about Ceres’ Bright Spots and Origins

Two newly published studies reveal that the bright spots on the dwarf planet Ceres are probably made of salt with bits of rock and frozen water mixed in. The researchers believe that when sunlight hits the blend, the ice sublimates into a misty haze above two of Ceres’s craters.

Ceres reveals some of its well-kept secrets in two new studies in the journal Nature, thanks to data from NASA’s Dawn spacecraft. They include highly anticipated insights about mysterious bright features found all over the dwarf planet’s surface.

In one study, scientists identify this bright material as a kind of salt. The second study suggests the detection of ammonia-rich clays, raising questions about how Ceres formed.

This representation of Ceres’ Occator Crater in false colors shows differences in the surface composition. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

About the Bright Spots

Ceres has more than 130 bright areas, and most of them are associated with impact craters. Study authors, led by Andreas Nathues at Max Planck Institute for Solar System Research, Göttingen, Germany, write that the bright material is consistent with a type of magnesium sulfate called hexahydrite. A different type of magnesium sulfate is familiar on Earth as Epsom salt.

Nathues and colleagues, using images from Dawn’s framing camera, suggest that these salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt, they say.

“The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice,” Nathues said.

An image of Occator Crater draped over a digital terrain model provides a 3-D-like perspective view of the impact structure. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

A New Look at Occator

The surface of Ceres, whose average diameter is 584 miles (940 kilometers), is generally dark — similar in brightness to fresh asphalt — study authors wrote. The bright patches that pepper the surface represent a large range of brightness, with the brightest areas reflecting about 50 percent of sunlight shining on the area. But there has not been unambiguous detection of water ice on Ceres higher-resolution data are needed to settle this question.

The inner portion of a crater called Occator contains the brightest material on Ceres. Occator itself is 60 miles (90 kilometers) in diameter, and its central pit, covered by this bright material, measures about 6 miles (10 kilometers) wide and 0.3 miles (0.5 kilometers) deep. Dark streaks, possibly fractures, traverse the pit. Remnants of a central peak, which was up to 0.3 miles (0.5 kilometers) high, can also be seen.

With its sharp rim and walls, and abundant terraces and landslide deposits, Occator appears to be among the youngest features on Ceres. Dawn mission scientists estimate its age to be about 78 million years old.

Study authors write that some views of Occator appear to show a diffuse haze near the surface that fills the floor of the crater. This may be associated with observations of water vapor at Ceres by the Herschel space observatory that were reported in 2014. The haze seems to be present in views during noon, local time, and absent at dawn and dusk, study authors write. This suggests that the phenomenon resembles the activity at the surface of a comet, with water vapor lifting tiny particles of dust and residual ice. Future data and analysis may test this hypothesis and reveal clues about the process causing this activity.

“The Dawn science team is still discussing these results and analyzing data to better understand what is happening at Occator,” said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.

A group of scientists from NASA’s Dawn mission suggests that when sunlight reaches Ceres’ Occator Crater, a kind of thin haze of dust and evaporating water forms there. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The Importance of Ammonia

In the second Nature study, members of the Dawn science team examined the composition of Ceres and found evidence for ammonia-rich clays. They used data from the visible and infrared mapping spectrometer, a device that looks at how various wavelengths of light are reflected by the surface, allowing minerals to be identified.

Ammonia ice by itself would evaporate on Ceres today, because the dwarf planet is too warm. However, ammonia molecules could be stable if present in combination with (i.e. chemically bonded to) other minerals.

The presence of ammoniated compounds raises the possibility that Ceres did not originate in the main asteroid belt between Mars and Jupiter, where it currently resides, but instead might have formed in the outer solar system. Another idea is that Ceres formed close to its present position, incorporating materials that drifted in from the outer solar system – near the orbit of Neptune, where nitrogen ices are thermally stable.

“The presence of ammonia-bearing species suggests that Ceres is composed of material accreted in an environment where ammonia and nitrogen were abundant. Consequently, we think that this material originated in the outer cold solar system,” said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome.

Oxo Crater, which is about 6 miles (9 kilometers) in diameter, is the second-brightest feature on Ceres. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

In comparing the spectrum of reflected light from Ceres to meteorites, scientists found some similarities. Specifically, they focused on the spectra, or chemical fingerprints, of carbonaceous chondrites, a type of carbon-rich meteorite thought to be relevant analogues for the dwarf planet. But these are not good matches for all wavelengths that the instrument sampled, the team found. In particular, there were distinctive absorption bands, matching mixtures containing ammoniated minerals, associated with wavelengths that can’t be observed from Earth-based telescopes.

The scientists note another difference is that these carbonaceous chondrites have bulk water contents of 15 to 20 percent, while Ceres’ content is as much as 30 percent.

“Ceres may have retained more volatiles than these meteorites, or it could have accreted the water from volatile-rich material,” De Sanctis said.

The study also shows that daytime surface temperatures on Ceres span from minus 136 degrees to minus 28 degrees Fahrenheit (180 to 240 Kelvin). The maximum temperatures were measured in the equatorial region. The temperatures at and near the equator are generally too high to support ice at the surface for a long time, study authors say, but data from Dawn’s next orbit will reveal more details.

As of this week, Dawn has reached its final orbital altitude at Ceres, about 240 miles (385 kilometers) from the surface of the dwarf planet. In mid-December, Dawn will begin taking observations from this orbit, including images at a resolution of 120 feet (35 meters) per pixel, infrared, gamma ray and neutron spectra, and high-resolution gravity data.


Two Studies Offer Fascinating Insights about Ceres, Its Bright Spots

In two new studies, published today in the journal Nature, the dwarf planet Ceres reveals some of its most eye-catching secrets. In the first study, researchers identify the bright material that is causing Ceres’ mysterious spots as hydrated magnesium sulfates. The second study suggests the detection of ammonia-rich clays, raising questions about how the dwarf planet formed.

This false-color image shows the dwarf planet Ceres. Scientists use false color to examine differences in surface materials. The color blue on Ceres is generally associated with bright material, found in more than 130 locations, and seems to be consistent with salts. Image credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.

Ceres has more than 130 bright areas, and most of them are associated with impact craters.

These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible, according to Dr Andreas Nathues of the Max Planck Institute for Solar System Research in Germany, who is the lead author on the first Nature study.

“These salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt,” Dr Nathues and co-authors said.

“The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice.”

The brightest material on the dwarf planet is found in the inner portion of a crater called Occator. Some images of this crater show a diffuse haze near the surface that fills the crater’s floor.

“This may be associated with observations of water vapor by NASA’s Herschel Space Observatory that were reported about a year ago,” the researchers said.

“The haze seems to be present in views during noon, local time, and absent at dawn and dusk.”

This suggests that the phenomenon resembles the activity at the surface of a comet, with water vapor lifting small particles of dust and residual ice.

“Of particular interest is a bright pit on the floor of crater Occator that exhibits probable sublimation of water ice, producing haze clouds inside the crater that appear and disappear with a diurnal rhythm. Slow-moving condensed-ice or dust particles may explain this haze,” Dr Nathues and his colleagues wrote in Nature.

Future data from NASA’s Dawn spacecraft may test this hypothesis and reveal clues about the process causing this activity.

Occator crater (center) appears to be among the youngest features on Ceres. Dawn mission scientists estimate its age to be about 78 million years old. Image credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.

In the second study, a team of scientists led by Dr Maria Cristina De Sanctis of the National Institute of Astrophysics in Rome analyzed the composition of Ceres and found evidence for clay minerals called ammoniated phyllosilicates. They used data from Dawn’s visible and infrared mapping spectrometer.

The presence of ammoniated compounds raises the possibility that the dwarf planet did not originate in the main asteroid belt, where it currently resides, but instead might have formed in the outer Solar System. Another hypothesis is that Ceres formed close to its present position, incorporating materials that drifted in from the outer Solar System.

“Our measurements indicate widespread ammoniated phyllosilicates across the surface, but no detectable water ice. Ammonia, accreted either as organic matter or as ice, may have reacted with phyllosilicates on Ceres during differentiation,” Dr De Sanctis and co-authors said.

“This suggests that material from the outer Solar System was incorporated into Ceres, either during its formation at great heliocentric distance or by incorporation of material transported into the main asteroid belt.”

The study also shows that daytime surface temperatures on the surface of the dwarf planet span from minus 136 degrees to minus 28 degrees Fahrenheit (minus 93 to minus 33 degrees Celsius).

“The maximum temperatures were measured in the equatorial region. The temperatures at and near the equator are generally too high to support ice at the surface for a long time, study authors say, but data from Dawn’s next orbit will reveal more details,” the scientists said.

A. Nathues et al. 2015. Sublimation in bright spots on (1) Ceres. Nature 528, 237-240 doi: 10.1038/nature15754

M. C. De Sanctis et al. 2015. Ammoniated phyllosilicates with a likely outer Solar System origin on (1) Ceres. Nature 528, 241-244 doi: 10.1038/nature16172


Dwarf planet Ceres boasts organic compounds, raising prospect of life

CAPE CANAVERAL, Fla. (Reuters) - A NASA spacecraft has detected carbon-based materials, similar to what may have been the building blocks for life on Earth, on the Texas-sized dwarf planet Ceres that orbits between Mars and Jupiter in the main asteroid belt, scientists said on Thursday.

The finding puts Ceres, a rock-and-ice world about 590 miles (950 km) in diameter, on a growing list of places in the solar system of interest to scientists looking for life beyond Earth. The list includes Mars and several ocean-bearing moons of Jupiter and Saturn.

The discovery, published in the journal Science, was made by a team of researchers using NASA’s Dawn spacecraft, which has been orbiting Ceres for nearly two years.

“I think these organic molecules are a long way from microbial life,” Dawn lead scientist Christopher Russell of the University of California Los Angeles (UCLA) wrote in an email to Reuters. “However, this discovery tells us that we need to explore Ceres further.” Ceres is the largest object in the asteroid belt and is located about three times farther from the sun than Earth. The composition of Ceres is thought to reflect the material present in parts of the solar system when it was forming some 4-1/2 billion years ago.

“The discovery indicates that the starting material in the solar system contained the essential elements, or the building blocks, for life,” Russell said.

“Ceres may have been able to take this process only so far. Perhaps to move further along the path took a larger body with more complex structure and dynamics,” like Earth, Russell added.

The organic material was found near a 31-mile-wide (50-km-wide) crater in Ceres’ northern hemisphere. Although the exact molecular compounds in the organics could not be identified, they matched tar-like minerals, such as kerite or asphaltite, the scientists wrote.

“Because Ceres is a dwarf planet that may still preserve internal heat from its formation period and may even contain a subsurface ocean, this opens the possibility that primitive life could have developed on Ceres itself,” planetary scientist Michael Kuppers of the European Space Astronomy Centre in Madrid wrote in an related essay in the journal Science.

Based on the location and type of organics found on Ceres, scientists ruled out the possibility they were deposited by a crashing asteroid or comet.

Lead researcher Maria Cristina De Sanctis of Italy’s National Institute for Astrophysics and colleagues suspect the material formed inside Ceres through hydrothermal activity, though how the organics reached the surface remains a mystery.


Dwarf planet Ceres boasts organic compounds, raising prospect of life

CAPE CANAVERAL, Fla. (Reuters) - A NASA spacecraft has detected carbon-based materials, similar to what may have been the building blocks for life on Earth, on the Texas-sized dwarf planet Ceres that orbits between Mars and Jupiter in the main asteroid belt, scientists said on Thursday.

The finding puts Ceres, a rock-and-ice world about 590 miles (950 km) in diameter, on a growing list of places in the solar system of interest to scientists looking for life beyond Earth. The list includes Mars and several ocean-bearing moons of Jupiter and Saturn.

The discovery, published in the journal Science, was made by a team of researchers using NASA’s Dawn spacecraft, which has been orbiting Ceres for nearly two years.

“I think these organic molecules are a long way from microbial life,” Dawn lead scientist Christopher Russell of the University of California Los Angeles (UCLA) wrote in an email to Reuters. “However, this discovery tells us that we need to explore Ceres further.” Ceres is the largest object in the asteroid belt and is located about three times farther from the sun than Earth. The composition of Ceres is thought to reflect the material present in parts of the solar system when it was forming some 4-1/2 billion years ago.

“The discovery indicates that the starting material in the solar system contained the essential elements, or the building blocks, for life,” Russell said. “Ceres may have been able to take this process only so far. Perhaps to move further along the path took a larger body with more complex structure and dynamics,” like Earth, Russell added.

The organic material was found near a 31-mile-wide (50-km-wide) crater in Ceres’ northern hemisphere. Although the exact molecular compounds in the organics could not be identified, they matched tar-like minerals, such as kerite or asphaltite, the scientists wrote.

“Because Ceres is a dwarf planet that may still preserve internal heat from its formation period and may even contain a subsurface ocean, this opens the possibility that primitive life could have developed on Ceres itself,” planetary scientist Michael Kuppers of the European Space Astronomy Centre in Madrid wrote in an related essay in the journal Science.

Based on the location and type of organics found on Ceres, scientists ruled out the possibility they were deposited by a crashing asteroid or comet.

Lead researcher Maria Cristina De Sanctis of Italy’s National Institute for Astrophysics and colleagues suspect the material formed inside Ceres through hydrothermal activity, though how the organics reached the surface remains a mystery.