Thermal Tomography of Asteroid Surface Structure

Abstract

Knowledge of the surface thermal inertia of an asteroid can provide insight into surface structure: porous material has a lower thermal inertia than rock. We develop a means to estimate thermal inertia values of asteroids and use it to show that thermal inertia appears to increase with spin period in the case of main-belt asteroids (MBAs). Similar behavior is found on the basis of thermophysical modeling for near-Earth objects (NEOs). We interpret our results in terms of rapidly increasing material density and thermal conductivity with depth, and provide evidence that thermal inertia increases by factors of 10 (MBAs) to 20 (NEOs) within a depth of just 10 cm. Our results are consistent with a very general picture of rapidly changing material properties in the topmost regolith layers of asteroids and have important implications for calculations of the Yarkovsky effect, including its perturbation of the orbits of potentially hazardous objects and those of asteroid family members after the break-up event. Evidence of a rapid increase of thermal inertia with depth is also an important result for studies of the ejecta-enhanced momentum transfer of impacting vehicles ("kinetic impactors") in planetary defense.

15 pages, 8 figures, accepted for publication in the Astrophysical Journal

References in corpus (5)

• Thermal inertia of near-Earth asteroids and implications for the magnitude of the Yarkovsky effect
• Main Belt Asteroids with WISE/NEOWISE: Near-Infrared Albedos
• Spitzer Observations of Spacecraft Target 162173 (1999 JU3)
• Thermal Infrared Observations of Asteroid (99942) Apophis with Herschel
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Cited by in corpus (3)

• Photometric survey, modelling, and scaling of long-period and low-amplitude asteroids
• Thermal properties of slowly rotating asteroids: Results from a targeted survey
• Asteroid shapes and thermal properties from combined optical and mid-infrared photometry inversion