The composition and origin of the C, P, and D asteroids: Water as a tracer of thermal evolution in the outer belt

Jones, Tina; Lebofsky, L. A.; Lewis, John S.; Marley, Mark S.

doi:10.1016/0019-1035(90)90184-b

Cited by 241 publications

(203 citation statements)

References 35 publications

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“…The scarcity and low contrast of absorption features in the VNIR prevents a detailed description of the mineralogy and association with meteorites of these asteroid types (B, C, Cb, Cg, Cgh, Ch). Spectroscopy in the 2.5-4 µm wavelength range, however, revealed the presence of hydration features (Lebofsky 1978;Jones et al 1990; Rivkin et al 2002). These features were interpreted as evidences for aqueous alteration, similar to that experienced by CI/CM parent bodies (Cloutis et al 2011a,b).…”

Section: Linking Small Bodies With Meteoritesmentioning

confidence: 99%

“…The recent recovery of the Almahata Sitta meteorite, originating from the impact of asteroid 2008 TC 3 on Earth in October 2008, indeed indicated that B-type could be associated with unusual Ureilite achondrites (Jenniskens et al 2009). Based on a comparison of the densities of (1) Ceres and (2) Pallas (used as archetypes for the definition of C and B taxonomic classes), Carry et al (2010a) had suggested that B-types were less hydrated than C-types; a hypothesis supported by the lack of signature of organic or icy material in their spectra (Jones et al 1990). …”

Section: C-complex and Sub-groupsmentioning

confidence: 99%

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Density of asteroids

Carry

2012

Planetary and Space Science

517

444

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The small bodies of our solar system are the remnants of the early stages of planetary formation. A considerable amount of information regarding the processes that occurred during the accretion of the early planetesimals is still present among this population. A review of our current knowledge of the density of small bodies is presented here. Density is indeed a fundamental property for the understanding of their composition and internal structure. Intrinsic physical properties of small bodies are sought by searching for relationships between the dynamical and taxonomic classes, size, and density. Mass and volume estimates for 287 small bodies (asteroids, comets, and transneptunian objects) are collected from the literature. The accuracy and biases affecting the methods used to estimate these quantities are discussed and best-estimates are strictly selected. Bulk densities are subsequently computed and compared with meteorite density, allowing to estimate the macroporosity (i.e., amount of voids) within these bodies. Dwarf-planets apparently have no macroporosity, while smaller bodies (<400 km) can have large voids. This trend is apparently correlated with size: C and S-complex asteroids tends to have larger density with increasing diameter. The average density of each Bus-DeMeo taxonomic classes is computed (DeMeo et al., 2009, Icarus 202). S-complex asteroids are more dense on average than those in the C-complex that in turn have a larger macroporosity, although both complexes partly overlap. Within the C-complex asteroids, B-types stand out in albedo, reflectance spectra, and density, indicating a unique composition and structure. Asteroids in the Xcomplex span a wide range of densities, suggesting that many compositions are included in the complex. Comets and TNOs have high macroporosity and low density, supporting the current models of internal structures made of icy aggregates. Although the number of density estimates sky-rocketed during last decade from a handful to 287, only a third of the estimates are more precise than 20%. Several lines of investigation to refine this statistic are contemplated, including observations of multiple systems, 3-D shape modeling, and orbital analysis from Gaia astrometry.Keywords: Minor planets, Mass, Volume, Density, Porosity Small bodies as remnants of planetesimalsThe small bodies of our solar System are the left-overs of the building blocks that accreted to form the planets, some 4.6 Gyr ago. They represent the most direct witnesses of the conditions that reigned in the proto-planetary nebula (Bottke et al. 2002a). Indeed, terrestrial planets have thermally evolved and in some cases suffered erosion (e.g., plate tectonic, volcanism) erasing evidence of their primitive composition. For most small bodies, however, their small diameter limited the amount of radiogenic nuclides in their interior, and thus the amount of energy for internal heating. The evolution of small bodies is therefore mainly exogenous, through eons of collisions, external heating, and bombardm...

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Section: Linking Small Bodies With Meteoritesmentioning

confidence: 99%

Section: C-complex and Sub-groupsmentioning

confidence: 99%

Density of asteroids

Carry

2012

Planetary and Space Science

517

444

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“…Due to their large heliocentric distances, the outer belt asteroids have experienced less heating and are expected to be of a more primitive composition. They may also contain a significant fraction of ice in their interiors (Jones et al 1990). Thus, these objects may provide a number of clues to the origin and evolution of the asteroid belt and to the formation of our planetary system.…”

Section: Introductionmentioning

confidence: 99%

(65) Cybele: detection of small silicate grains, water-ice, and organics

Licandro

Campins

Kelley

et al. 2010

A&A

109

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Context. (65) Cybele is the most representative member of a population of primitive asteroids in the outer edge of the main belt, the Cybele asteroids. Recent dynamical models suggest that a significant fraction of them originated in the primordial transneptunian disk, so the study of the physical properties of these asteroids is potentially a useful test of these models. Aims. Our aim is to obtain information on the surface composition of this asteroid. In particular we want to obtain information on the composition and properties of the regolith and the possible presence of ices and organic materials. Methods. We present 2-4 μm and 5-14 μm spectroscopy of (65) Cybele obtained with the NASA IRTF telescope and Spitzer Space Telescope respectively. We compare the results with spectra of Trojan asteroids and asteroid (24) Themis. We analyze the 2-4 μm spectrum using scattering models and we apply thermal models to the 5-14 μm data. Results. The 2-4 μm spectrum of (65) Cybele presents an absorption band centered at ∼3.1 μm and more weaker bands in the 3.2-3.6 μm region, very similar to those observed in (24) Themis. No hydrated silicates are detected. From the spectrum in the 5-14 μm region an effective diameter D = 290 ± 5 km, a beaming paramete η = 0.967 ± 0.014, and a geometric visible albedo p V = 0.05 ± 0.01 are derived using the NEATM thermal model. The emisivity spectrum in the 5-14 μm range exhibits an emission plateau at about 9 to 12 μm with an spectral contrast of ∼5%. This emission is similar to that of Trojan asteroids and active comets and may be due to small silicate grains being imbedded in a relatively transparent matrix, or to a very under-dense (fairy-castle) surface structure. The lower amplitude of the silicate emission in Cybele's spectrum with respect to that of Trojan asteroids could be attributed to larger dust particles and/or a slightly denser structure. Conclusions. The surface of (65) Cybele is covered by a fine anhydrous silicate grains mantle, with a small amount of water ice and complex organic solids. This is similar to comet surface where non-equilibrium phases coexist. The presence of water-ice and anhydrous silicates is indicative that hydration did not happened or is incomplete, suggesting that the temperatures were always sufficiently low.

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“…(e.g., Jones et al, 1990;Gaffey et al, 2002). While the known population of small bodies has grown by orders of magnitude recently (currently N ∼ 5×10 5 ) because of new surveys and instruments (Minor Planet Center, 2010), and many new dynamical complexities among asteroid populations have been revealed (e.g., Bottke et al, 2002), the overall trend in composition remains an important observational constraint.…”

Section: Outer Solar System Satellites and Ringsmentioning

confidence: 99%

Water on Planets

Bell

2009

Proc. IAU

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Abstract.Water is an abundant molecule in the Cosmos. It has exploitable and unique spectroscopic and physical properties and has been found to be ubiquitous in places that we would expect in the standard model of solar system formation and nebular condensation: beyond the snow line in outer solar system planets, moons, asteroids, and comets. However, water is also an important constituent of planetary bodies (dominating at least one of their surfaces) in the inner solar system, likely indicating significant mixing between inner and outer solar system reservoirs of water during planetary accretion and the early history of the solar system. Water has played a critical role in the differential evolution of the terrestrial planets Venus, Earth, and Mars, and the concept of the "habitable zone" where liquid water could be stable on an Earth-like planet provides a starting point for assessing the habitability of worlds in our solar system and beyond. Examples of potentially habitable environments outside this zone in our own solar system warn us that this concept should only be a guide, however-important exceptions will no doubt occur. Recent discoveries of past liquid water and abundant present subsurface ice on Mars, of water reservoirs in unexpected places like the poles of Mercury and the Moon and the subsurface of Enceladus, of water in circumstellar disks and in the atmospheres of extrasolar planets, and the expectation of the discovery of water on Earth-like worlds in the habitable zones around other stars make this an exciting time in the study of water on planets both in our own solar system, and beyond.

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The composition and origin of the C, P, and D asteroids: Water as a tracer of thermal evolution in the outer belt

Cited by 241 publications

References 35 publications

Density of asteroids

Density of asteroids

(65) Cybele: detection of small silicate grains, water-ice, and organics

Water on Planets

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