Structural Transitions in Amorphous Water Ice and Astrophysical Implications

• DOI: 10.1126/science.11539186
• Publication Date: 2006-10-06T00:01:25Z
• Authors: Peter Jenniskens; David F. Blake
• Keywords: Amorphous ice; Polyamorphism; Water ice; Interstellar ice

Selected area electron diffraction is used to monitor structural changes of vapor-deposited water ice in vacuum during warm-up from 15 188 K. A progression three amorphous forms found with well-defined transitions. The formation a high-density form (I h) at K confirmed, and the transition more familiar low-density l) occurs gradually over range 38 68 At 131 K, transforms into third r), which precedes crystallization cubic c ) coexists metastably I 148 until least These transformations can be explain hitherto anomalous properties astrophysical ices. h l responsible for diffusion recombination radicals ultraviolet-photolyzed interstellar ices low temperatures. occurrence persistence r explains gas retention release water-rich temperatures above 150