154-3 From 25 to 1650°C and Back Again: Thermal and Rheological Properties of Ordinary Chondrites to Improve Thermophysical Modeling

Session: Asteroid Observations, Return Missions, and Meteoritics: Interweaving Perspectives and Data (Posters)

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Ordinary chondrites—among the most abundant meteorites in planetary collections—offer key insights into the early thermal and structural evolution of the Solar System. Despite their importance in reconstructing parent body processes, comprehensive datasets on their thermophysical properties remain scarce, especially at high temperatures. Parameters including thermal diffusivity, heat capacity, and viscosity are critical for simulating meteoroid atmospheric entry, impact heating, internal differentiation, and metamorphism. However, existing models often rely on generalized or extrapolated values due to limited measurements. Our study addresses this gap by experimentally measuring these properties across a wide thermal range using multiple laboratory techniques on both H and LL ordinary chondrites (Tamdakht and Kheneg Ljouâd, respectively).

Density (ρ) was measured using a helium pycnometer. Heat capacity (CP) and thermal diffusivity (D) were obtained via laser flash analysis (LFA) from 25°C to 1200°C. Thermal conductivity (k) is provided by the relation k = DρCP. Attempts to extend heat capacity data acquisition up to 1650°C using Differential Scanning Calorimetry (DSC) were challenged by crucible-sample incompatibility.

LFA results revealed thermally dependent behavior, with notable differences between the H and LL samples. Both Tamdakht (H) and Kheneg Ljouâd (LL) showed initial decreases in thermal diffusivity after heating to 700°C. Tamdakht’s diffusivity fell from 0.596 to 0.511 mm²/s (25°C baseline), while Kheneg Ljouâd dropped from 0.311 to 0.282 mm²/s. Conductivity followed, reaching lows of 1.956 W/m·K for Tamdakht and 0.877 W/m·K for Kheneg Ljouâd. Above 700°C, both samples showed irreversible increases in thermal properties. Tamdakht’s diffusivity rose from 0.799 to 1.261 mm²/s after a 1200°C run, and to 1.33 mm²/s after a 1250°C run—on the same sample. Kheneg Ljouâd increased from 0.311 to 0.48 mm²/s post-1200°C. Conductivity rose in parallel, from 2.743 to 4.566 W/m·K in Tamdakht, and from 0.966 to 1.455 W/m·K in Kheneg Ljouâd. These changes likely reflect microstructural reordering, minor devolatilization, or incipient phase transitions at elevated temperatures.

These findings emphasize the importance of high-temperature thermal cycling in accurately capturing chondritic material behavior. By filling a critical gap in meteoritic property databases, these data improve modeling of energy transport and material response in early Solar System bodies along with terrestrial impact processes.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8359

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