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

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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“…The data that support the findings of this study are openly available in [Zenodo] at https://doi.org/10.5281/zenodo.3588334 (Soini et al. ).…”

Section: Availability Of Datasupporting

confidence: 70%

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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“…Our computed thermal conductivity values agree with the Soini et al (2020) model fits to essentially the same dataset as ours. We accounted for temperature-dependent thermal conductivity among these samples by bootstrapping our k grain calculations with the data compiled in Flynn et al (2017).…”

Section: Thermal Conductivitysupporting

confidence: 82%

“…Data presented by Soini et al (2020) shows that the thermal conductivities of ordinary and carbonaceous chondrites are in agreement when the sample porosities are taken into account. Because we account for sample porosities and are using grain densities, we use the same zero-porosity thermal conductivity value for carbonaceous chondrites and ordinary chondrites, with the exception of CM chondrites.…”

Section: Thermal Conductivitymentioning

confidence: 77%

“…Laboratory measurements of meteorite thermal conductivities reveal dependence on the material porosity and temperature. In their review paper of thermal conductivites, Flynn et al (2017) show that laboratory measurements of thermal conductivity do not change significantly in the temperature range from 100 and 300 K, but approach zero at 0 K. Additionally, void spaces can significantly impede the net solid-state heat flow within a meteorite sample (Soini et al, 2020). To account for porosity effects, we estimate the thermal conductivity at zero porosity using data collected at the same temperature.…”

Section: Thermal Conductivitymentioning

confidence: 99%

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Thermophysical Investigation of Asteroid Surfaces II: Factors Influencing Grain Size

MacLennan,

Emery

2021

Preprint

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Asteroid surfaces are subjected to mechanical weathering processes that result in the development and evolution of regolith. Two proposed mechanisms-impact bombardment and thermal fatigue-have been proposed as viable and dominant weathering processes. Previously, we compiled and estimated thermal inertias of several hundred asteroids (mostly in the main-belt) for which we determined dependencies on temperature, diameter, and rotation period. In this work, we estimate grain sizes of asteroid regoliths from this large thermal inertia dataset using thermal conductivity models. Following our previous work we perform multi-variate linear model fits to the grain size dataset and quantify its dependency on diameter and rotation period. We find that the best-fit model fit indicates that asteroid grain sizes are inversely dependent on object size for <10 km asteroids and exhibits no relationship above this size cutoff. Rotation period and grain size show a positive relationship when the rotation period is greater than ∼5 hr, and an inverse relationship below this rotation period. We conclude that both impact weathering and thermal fatigue are significant regolith evolution mechanisms. Furthermore, we run post-hoc t-tests between spectral groups to identify compositional differences among our asteroid set. Notably, suspected metal-rich, M-type and E-type asteroids have larger than expected grain sizes, and P-types have distinctly smaller grains than other groups.

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“…Density is also a parameter in determining rock properties such as mechanical strength, which is key to understanding the physical evolution of asteroids (Scheeres & Sánchez, 2018). Porosity, which is intrinsically linked to density, is an important factor in understanding processes such as asteroid compaction, lithification, breakup, and reassembly (Consolmagno et al, 2008;Soini et al, 2020). Together, density and porosity are key in understanding impact shock and terrestrial weathering processes (Consolmagno & Britt, 1998;Ostrowski & Bryson, 2019).…”

Section: Densitymentioning

confidence: 99%

Nondestructive determination of the physical properties of Antarctic meteorites: Importance for the meteorite—parent body connection

Harvey,

MacArthur,

Joy

et al. 2023

Meteorit & Planetary Scien

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Photogrammetry is a low‐cost, nondestructive approach for producing 3‐D models of meteorites for the purpose of determining sample bulk density. Coupled with the use of a nondestructive magnetic susceptibility/electrical conductivity field probe, we present measurements for the interrogation of several physical properties, on a set of Antarctic meteorites. Photogrammetry is an effective technique over a range of sample sizes, with meteorite bulk density results that are closely comparable with literature values, determined using Archimedean glass bead or laser scanning techniques. The technique is completely noncontaminating and suitable for the analysis of rare or fragile samples, although there are limitations for analyzing reflective samples. It is also flexible, and, with variations in equipment setup, may be appropriate for samples of a wide range of sizes. X‐ray computed tomography analyses of the same meteorite samples yielded slightly different bulk density results, predominantly for samples below 10 g, although the reason for this is unclear. Such analyses are expensive and potentially damaging to certain features of the sample (e.g., organic compounds), but may be useful in expanding the measurements to accommodate an understanding of internal voids within the sample, lending itself to measurement of grain density. Measurements of bulk density are valuable for comparisons with estimates of the bulk densities of asteroids that are suggested as meteorite parent bodies.

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

Cited by 3 publications

References 33 publications

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

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

Thermophysical Investigation of Asteroid Surfaces II: Factors Influencing Grain Size

Nondestructive determination of the physical properties of Antarctic meteorites: Importance for the meteorite—parent body connection

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