Radiation-induced amorphization of crystalline ice

M. Famá, M. J. Loeffler, U. Raut, R. A. Baragiola

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

We study radiation-induced amorphization of crystalline ice, analyzing the results 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 μm 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 reflectance absorption spectra measured between 1.4 and 2.2 μm for amorphous and crystalline ices irradiated with 225 keV protons at 80 K. We found that, after irradiation with 1015 protons cm-2, 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.

Original languageEnglish (US)
Pages (from-to)314-319
Number of pages6
JournalIcarus
Volume207
Issue number1
DOIs
StatePublished - May 2010
Externally publishedYes

Keywords

  • Ices, IR spectroscopy
  • Infrared observations
  • Kuiper belt
  • Satellites, Surfaces

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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