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The surface properties of small asteroids: Peculiar Betulia - a case study

Harris, Alan W. and Mueller, Michael and Delbo, Marco and Bus, Schelte J. (2005) The surface properties of small asteroids: Peculiar Betulia - a case study. Icarus: International Journal of Solar System Studies, 179 (1), pp. 95-108. Elsevier. DOI: 10.1016/j.icarus.2005.05.010. ISSN 0019-1035.

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Abstract

We present the results of extensive thermal–infrared observations of the C-type near-Earth Asteroid (1580) Betulia obtained in June 2002 with the 3-m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Betulia is a highly unusual object for which earlier radiometric observations, interpreted on the basis of simple thermal models, indicated a surface of high thermal inertia. A high thermal inertia implies a lack of thermally insulating regolith. Radiometric observations of other asteroids of comparable size indicate that regolith is present in nearly all cases. Knowledge of the surface thermal properties of small near-Earth asteroids is crucial for meaningful calculations of the Yarkovsky effect, which is invoked to explain the delivery of collisional fragments from the main belt into near-Earth orbits, and apparently has a significant influence on the orbital evolution of potentially hazardous near-Earth asteroids. Furthermore, apart from being an indicator of the presence of thermally insulating regolith on the surface of an asteroid, the thermal inertia determines the magnitude of the diurnal temperature variation and is therefore of great importance in the design of instrumentation for lander missions to small asteroids. In the case of Betulia our database is sufficiently broad to allow the use of more sophisticated thermal models than were available for earlier radiometric observations. The measured fluxes have been fitted with thermal-model emission continua to determine the asteroid's size and geometric albedo, pv. Fits obtained with a new thermophysical model imply an effective diameter of 4.57±0.46 km and an albedo of 0.077±0.015 and indicate a moderate surface thermal inertia of around 180 J m<sup>−2</sup> s<sup>−0.5</sup> K<sup>−1</sup>. It is difficult to reconcile our results with earlier work, which indicate a larger diameter for Betulia and a high-thermal-inertia surface of bare rock.

Document Type:Article
Additional Information: LIDO-Berichtsjahr=2005,
Title:The surface properties of small asteroids: Peculiar Betulia - a case study
Authors:
AuthorsInstitution or Email of Authors
Harris, Alan W.UNSPECIFIED
Mueller, MichaelUNSPECIFIED
Delbo, MarcoOsservatorio Astronomico di Torino, Pino Torinese, Italy
Bus, Schelte J.Institute for Astronomy, Hilo, HI, USA
Date:2005
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
In ISI Web of Science:Yes
Volume:179
DOI: 10.1016/j.icarus.2005.05.010
Page Range:pp. 95-108
Publisher:Elsevier
ISSN:0019-1035
Status:Published
Keywords:Asteroids, Infrared observations, Photometry, Spectrophotometry
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EW - Erforschung des Weltraums
DLR - Research area:Space
DLR - Program:W EW - Erforschung des Weltraums
DLR - Research theme (Project):W - Vorhaben Asteroiden und Kometen (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Asteroids and Comets
Deposited By: Susanne Pieth
Deposited On:06 Dec 2005
Last Modified:14 Jan 2010 20:19

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