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Radiation-Induced Amorphization of Crystalline IceWe study radiation-induced amorphization of crystalline ice, ana lyzing the resu lts of three decades of experiments with a variety of projectiles, irradiation energy, and ice temperature, finding a similar trend of increasing resistance of amorphization with temperature and inconsistencies in results from different laboratories. We discuss the temperature dependence of amorphization in terms of the 'thermal spike' model. We then discuss the common use of the 1.65 micrometer infrared absorption band of water as a measure of degree of crystallinity, an increasingly common procedure to analyze remote sensing data of astronomical icy bodies. The discussion is based on new, high quality near-infrared refl ectance absorption spectra measured between 1.4 and 2.2 micrometers for amorphous and crystalline ices irradiated with 225 keV protons at 80 K. We found that, after irradiation with 10(exp 15) protons per square centimeter, crystalline ice films thinner than the ion range become fully amorphous, and that the infrared absorption spectra show no significant changes upon further irradiation. The complete amorphization suggests that crystalline ice observed in the outer Solar System, including trans-neptunian objects, may results from heat from internal sources or from the impact of icy meteorites or comets.
Document ID
20110013466
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Fama, M.
(Virginia Univ. Charlottesville, VA, United States)
Loeffler, M. J.
(Virginia Univ. Charlottesville, VA, United States)
Raut, U.
(Virginia Univ. Charlottesville, VA, United States)
Baragiola, R. A.
(Virginia Univ. Charlottesville, VA, United States)
Date Acquired
August 25, 2013
Publication Date
November 10, 2009
Publication Information
Publication: Icarus
Publisher: Elsevier, Inc.
Volume: 207
Issue: 1
ISSN: 0019-1035
Subject Category
Astrophysics
Report/Patent Number
GSFC.JA.4461.2011
Distribution Limits
Public
Copyright
Other

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