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Updated: Jun 24, 2026
08:16
Ice Generation and the Heat and Mass Transfer Phenomena of Introducing Water to a Cold Bath of Brine
Published on: March 13, 2017
Structural transitions in amorphous water ice and astrophysical implications
1NASA/Ames Research Center, Moffett Field, CA 94035, USA.
Science (New York, N.Y.)
|August 5, 1994
Summary
Water ice undergoes structural changes, transforming through three amorphous forms (Iah, Ial, Iar) during warming. These transformations explain unusual properties observed in astrophysical ices.
Area of Science:
- Materials Science
- Astrochemistry
- Physical Chemistry
Background:
- Amorphous water ice is prevalent in astrophysical environments.
- Understanding its structural transitions is crucial for interpreting observations of interstellar ices.
Purpose of the Study:
- To investigate the structural transformations of vapor-deposited water ice under vacuum during warming.
- To identify and characterize different amorphous phases of water ice and their transition temperatures.
Main Methods:
- Selected area electron diffraction (SAED) was employed to monitor structural changes.
- Vapor-deposited water ice was warmed from 15 K to 188 K under vacuum.
Main Results:
- Three distinct amorphous water ice forms were identified: high-density amorphous ice (Iah), low-density amorphous ice (Ial), and a third form (Iar).
- Transitions occurred at specific temperature ranges: Iah to Ial (38–68 K), and formation of Iar at 131 K.
- Iar coexists with cubic ice (Ic) from 148 K to at least 188 K.
Conclusions:
- The identified amorphous ice transformations provide explanations for anomalous properties of astrophysical ices.
- The Iah to Ial transition is linked to radical diffusion and recombination in interstellar ices.
- The Iar phase explains anomalous gas retention and release in water-rich ices at elevated temperatures.
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