Abstract Boulders covering the surfaces of asteroids Bennu and Ryugu have apparent thermal inertias substantially lower than their meteorite analogs. This has led to the inference that boulders on Bennu may be unlike any known meteorite. However, samples returned from Ryugu have a thermal inertia 3.5 times higher than the apparent thermal inertia inferred from remote sensing observations. Here I use thermal modeling to show that shallow subsurface fractures parallel to the surface have a substantial effect on surface temperature and can explain this discrepancy. Thermal fatigue modeling predicts similar fractures. Fracture depth has a much larger effect on surface temperature than the composition of the material. The modeling presented here, and the thermal diffusivity measured in Ryugu samples, suggest that the samples returned from Bennu are also likely to have a thermal inertia closer to their meteorite analogs than to the thermal inertia inferred from remote sensing observations.
Observations from the Little Bunker
Last updated: November 30, 2025 04:25 AM
Atmospheric CO₂
426.8 ppm
+18.1
ppm/year
Atmospheric CH₄
1927.61 ppb
+2.73
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
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8.1 billion
+67
million/year