While liquid form of water is essential for Life that we know off, abundancy of liquid water in the Universe seems to be not the most, but in fact the least. Most of water is observed to exist in the solid form, commonly called as “ice”. This talk will review water-ice and trace its travel from interstellar molecular clouds to present-day icy bodies in our solar system. Several questions will be posed, of which only a few have concrete answers. Some of these questions are directed towards physical properties of ice, namely, amorphous and crystalline. Another question is whether water-ice exists in its pure form at microstructural level or intimately mixed with minor components in the interstellar ice grains? Answer to this question will have important implications to organic chemistry in interstellar ice. Other questions that follow these are: Why Kuiper Belt Objects (KBOs) in our solar system are covered with crystalline water-ice? What is a comet’s nucleus interior made of – amorphous or crystalline ice? How does ice evolve in a protoplanetary disk? What is the role of water-ice in the ice chemistry when exposed to radiation? What are thermally-induced chemical reactions that occur in the bulk of ice when not exposed to radiation, but remains under constant temperature over billions of years? Can clathrates be formed under vacuum conditions? If yes, what is the loading ratio of trapped species to water? How many such species can be trapped in water-ice? We have made tremendous advances in our understanding of water in its ice form, including the high-pressure ice (which will not be discussed in this review). But, many more questions remain unanswered.

Water-ice: Quest to understand its physical forms and chemical processes

2019 Fall National Meeting

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