Asteroid Interiors and Morphology

Scheeres, Daniel J.; Britt, D. T.; Carry, B.; Holsapple, K. A.

doi:10.2458/azu_uapress_9780816532131-ch038

Cited by 78 publications

(78 citation statements)

References 109 publications

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“…The derived density therefore suggests a null internal porosity, consistent with an intact internal structure. Hebe hence appears to reside in the volumetric and struc- tural transitional region between the compact and gravity-shaped dwarf planets, and the medium-sized asteroids (∼10-100 km in diameter) with fractured interior (Carry, 2012;Scheeres et al, 2015). However, due to the current large mass uncertainty that dominates the uncertainty of the bulk density, the possibility of higher internal porosity cannot be ruled out.…”

Section: D Shape Volume and Densitymentioning

confidence: 97%

3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites

Marsset

Carry

Dumas

et al. 2017

A&A

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Context. The high-angular-resolution capability of the new-generation ground-based adaptive-optics camera SPHERE at ESO VLT allows us to assess, for the very first time, the cratering record of medium-sized (D∼100-200 km) asteroids from the ground, opening the prospect of a new era of investigation of the asteroid belt's collisional history. Aims. We investigate here the collisional history of asteroid (6) Hebe and challenge the idea that Hebe may be the parent body of ordinary H chondrites, the most common type of meteorites found on Earth (∼34% of the falls). Methods. We observed Hebe with SPHERE as part of the science verification of the instrument. Combined with earlier adaptiveoptics images and optical light curves, we model the spin and three-dimensional (3D) shape of Hebe and check the consistency of the derived model against available stellar occultations and thermal measurements. Results. Our 3D shape model fits the images with sub-pixel residuals and the light curves to 0.02 mag. The rotation period (7.274 47 h), spin (ECJ2000 λ,β of 343 • ,+47 • ), and volume-equivalent diameter (193 ± 6 km) are consistent with previous determinations and thermophysical modeling. Hebe's inferred density is 3.48 ± 0.64 g.cm −3 , in agreement with an intact interior based on its H-chondrite composition. Using the 3D shape model to derive the volume of the largest depression (likely impact crater), it appears that the latter is significantly smaller than the total volume of close-by S-type H-chondrite-like asteroid families. Conclusions. Our results imply that (6) Hebe is not the most likely source of H chondrites. Over the coming years, our team will collect similar high-precision shape measurements with VLT/SPHERE for ∼40 asteroids covering the main compositional classes, thus providing an unprecedented dataset to investigate the origin and collisional evolution of the asteroid belt.

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Section: D Shape Volume and Densitymentioning

confidence: 97%

3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites

Marsset

Carry

Dumas

et al. 2017

A&A

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“…Most of the large mass stony meteorites are products of showers whose fragments are compositionally homogeneous implying small stony bodies are usually homogeneous and weak rubble piles (Scheeres et al. ). While the individual components can be very strong, the asteroid as a whole is very weak (Scheeres et al.…”

Section: Introductionmentioning

confidence: 99%

“…While the individual components can be very strong, the asteroid as a whole is very weak (Scheeres et al. ).…”

Section: Introductionmentioning

confidence: 99%

“…According to Ostrowski and Bryson (2017), porosity correlates negatively with shear modulus and Young's modulus in particular providing clues on mechanical properties of chondrite bodies. Most of the large mass stony meteorites are products of showers whose fragments are compositionally homogeneous implying small stony bodies are usually homogeneous and weak rubble piles (Scheeres et al 2015). While the individual components can be very strong, the asteroid as a whole is very weak (Scheeres et al 2015).…”

Section: Introduction Generalmentioning

confidence: 99%

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Thermal and porosity properties of meteorites: A compilation of published data and new measurements

Soini

Kukkonen

Kohout

et al. 2020

Meteorit & Planetary Scien

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We report direct measurements of thermal diffusivity and conductivity at room temperature for 38 meteorite samples of 36 different meteorites including mostly chondrites, and thus almost triple the number of meteorites for which thermal conductivity is directly measured. Additionally, we measured porosity for 34 of these samples. Thermal properties were measured using an optical infrared scanning method on samples of cm‐sizes with a flat, sawn surface. A database compiled from our measurements and literature data suggests that thermal diffusivities and conductivities at room temperature vary largely among samples even of the same petrologic and chemical type and overlap among, for example, different ordinary chondrite classes. Measured conductivities of ordinary chondrites vary from 0.4 to 5.1 W m−1 K−1. On average, enstatite chondrites show much higher values (2.33–5.51 W m−1 K−1) and carbonaceous chondrites lower values (0.5–2.55 W m−1 K−1). Mineral composition (silicates versus iron‐nickel) and porosity control conductivity. Porosity shows (linear) negative correlation with conductivity. Variable conductivity is attributed to heterogeneity in mineral composition and porosity by intra‐ and intergranular voids and cracks, which are important in the scale of typical meteorite samples. The effect of porosity may be even more significant for thermal properties than that of the metal content in chondrites.

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“…DEM simulations are far more computationally intensive, but have the advantage that they show a dynamical evolution and the material parameters are generally known and implemented. In addition to topics common to granular mechanics research such as particle size segregation, stress states, and penetrometry, the granular physics of asteroids raises several unique challenges including: rotation induced deformation and disruption, collisional evolution, interior heterogeneities, gravitational tide induced deformation, interior heterogeneities, cratering, and sampling mechanisms, among the most important [12,13].…”

Section: Current Questions and Hypothesesmentioning

confidence: 99%