@article{7ee023387d6a46edb034dac1cc0cef38,
title = "Observing the variation of asteroid thermal inertia with heliocentric distance",
abstract = "Thermal inertia is a useful property to characterize a planetary surface, since it can be used as a qualitative measure of the regolith grain size. It is expected to vary with heliocentric distance because of its dependence on temperature. However, no previous investigation has conclusively observed a change in thermal inertia for any given planetary body. We have addressed this by using NEOWISE data and the Advanced Thermophysical Model to study the thermophysical properties of the near-Earth asteroids (1036) Ganymed, (1580) Betulia, and (276 049) 2002 CE26 as they moved around their highly eccentric orbits. We confirm that the thermal inertia values of Ganymed and 2002 CE26 do vary with heliocentric distance, although the degree of variation observed depends on the spectral emissivity assumed in the thermophysical modelling. We also confirm that the thermal inertia of Betulia did not change for three different observations obtained at the same heliocentric distance. Depending on the spectral emissivity, the variations for Ganymed and 2002 CE26 are potentially more extreme than that implied by theoretical models of heat transfer within asteroidal regoliths, which might be explained by asteroids having thermal properties that also vary with depth. Accounting for this variation reduces a previously observed trend of decreasing asteroid thermal inertia with increasing size, and suggests that the surfaces of small and large asteroids could be much more similar than previously thought. Furthermore, this variation can affect Yarkovsky orbital drift predictions by a few tens of per cent.",
keywords = "(1580) Betulia, (276 049) 2002 CE26, Asteroids: Individual: (1036) Ganymed, Celestial mechanics, Methods: Numerical, Minor planets, Radiation mechanisms: Thermal",
author = "B. Rozitis and Green, {S. F.} and E. MacLennan and Emery, {J. P.}",
note = "Funding Information: BR acknowledges support from the Royal Astronomical Society in the form of a research fellowship. SFG acknowledges the financial support of the Science & Technology Facilities Council (grants ST/L000776/1 and ST/P000657/1). We like to thank Jens Biele (DLR) for stimulating discussions about asteroid thermal inertia. We also thank the anonymous reviewer for comments that helped improve the manuscript. This publication uses data products from NEOWISE, a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of NASA.We made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory/California Institute of Technology under a contract with NASA. This publication is also based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory/California Institute of Technology under a contract with NASA. The CASSIS is a product of the IRS instrument team, supported by NASA and JPL Funding Information: BR acknowledges support from the Royal Astronomical Society in the form of a research fellowship. SFG acknowledges the financial support of the Science & Technology Facilities Council (grants ST/L000776/1 and ST/P000657/1). We like to thank Jens Biele (DLR) for stimulating discussions about asteroid thermal inertia. We also thank the anonymous reviewer for comments that helped improve the manuscript. This publication uses data products from NEOWISE, a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of NASA. We made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory/California Institute of Technology under a contract with NASA. This publication is also based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory/California Institute of Technology under a contract with NASA. The CASSIS is a product of the IRS instrument team, supported by NASA and JPL. Publisher Copyright: {\textcopyright} 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.",
year = "2018",
month = jun,
day = "21",
doi = "10.1093/mnras/sty640",
language = "English (US)",
volume = "477",
pages = "1782--1802",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "2",
}