Ammonia–water ice laboratory studies relevant to outer Solar System surfaces

Ammonia–water ice laboratory studies relevant to outer Solar System surfaces

Although water- and ammonia-ices have been observed or postulated as important components of the icy surfaces of planetary satellites in the outer Solar System, significant gaps exist in our knowledge of the spectra and behavior of such mixtures under astrophysical conditions. To that end, we have c...

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Bibliographic Details
Published in:Icarus (New York, N.Y. 1962) Vol. 190; no. 1; pp. 260 - 273
Main Authors: Moore, M.H., Ferrante, R.F., Hudson, R.L., Stone, J.N.
Format: Journal Article
Language:English
Published: San Diego, CA Elsevier Inc 01-09-2007
Elsevier
Subjects:
Astronomy
Charon
Earth, ocean, space
Exact sciences and technology
Ices
Satellites
Solar system
Spectroscopy
surfaces
Trans-neptunian objects
Spectroscopy
Charon
Satellites
Ices
Trans-neptunian objects
Laboratory study
surfaces; Spectroscopy
Ice
Spectral line shift
Thermal stability
Ammonia
Thermal radiation
Pluto satellite
Radiation temperature
Natural satellites
Positions
Solar system
Ices; Charon; Trans-neptunian objects; Satellites
Planetary surfaces
Low temperature
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Summary:Although water- and ammonia-ices have been observed or postulated as important components of the icy surfaces of planetary satellites in the outer Solar System, significant gaps exist in our knowledge of the spectra and behavior of such mixtures under astrophysical conditions. To that end, we have completed low-temperature spectroscopic studies (1–20 μm) of water–ammonia mixtures, with an emphasis on features in the near-IR, a region which is accessible to ground-based observations. The influences of composition, formation temperature, thermal- and radiation-processing, and phase (crystalline or amorphous) of the components were examined. Spectra of both pure NH 3 and H 2O–NH 3 icy mixtures with ratios from 0.7 to 57 were measured at temperatures from 10 to 120 K. Conditions for the formation and thermal stability of the ammonia hemihydrate (2NH 3⋅H 2O) and the ammonia monohydrate (NH 3⋅H 2O) have been examined. Band positions of NH 3 in different H 2O-ices and major band positions of the hydrates were measured. We report spectral shifts that depend on concentration and temperature. The radiation-induced amorphization of the hemihydrate was observed and the radiation destruction of NH 3 in H 2O-ices was measured. Implications of these results for the formation, stability, and detection of ammonia on outer satellite surfaces are discussed.
Bibliography:ObjectType-Article-1
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ISSN:0019-1035
1090-2643
DOI:10.1016/j.icarus.2007.02.020