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Project Progress

Our goal ultimate goal is to investigate the formation of biological molecules in water-rich environments. Water ice serves as the energy-transfer medium and active participant in a variety of radiation-driven chemistry reactions thought to be important in either the interstellar medium or the primordial solar nebula. The processes for formation of biological molecules in space are fairly complicated. In order to understand the detailed mechanism behind it, we have to do experiment step by step. As the first step for understanding the formation of those molecules in water-rich environments, we choose to investigate the irradiation of pure water ice itself and the formation of bio-molecules without water involved. Our project progress includes three parts: (1) commission of an ultra high vacuum experimental apparatus; (2) investigation of pure water ice; (3) formation of small biologically important molecules in water-free environments.

Since our last report, we have improved our experimental apparatus significantly (Figs. 1 and 2). The lowest pressure in the main chamber can be pumped down to 5.0_10^-11 torr. This can minimize the impurities in the low temperature ices. It is extremely important for mechanism study of chemical reactions in low temperature ices under clean conditions without surface contaminations.

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We have conducted a systematic study on electron irradiation of pure water ice. The formation of molecular hydrogen, molecular oxygen, and hydrogen peroxide together with hydrogen and oxygen atoms had been investigated in the experiments (Figs. 3 and 4). We also proposed mechanisms how these molecules are formed. The experimental results of pure water ice might also help the understanding of the cosmic ray processing of water ices in the interstellar medium as well as the cosmic ray and solar wind processing of water ices in Kuiper Belt Objects, comets, planetary surfaces and satellite surfaces.

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In the experiments of water-free ices, we investigated the formation of the amino acid glycine (NH₂CH₂COOH) and its isomer (CH₃NHCOOH) in extraterrestrial ices (Fig 5 and Fig 6). We studied also the formation of acetaldehyde (CH₃CHO), ethylene oxide (c-C₂H₄O), and vinyl alcohol (C₂H₃OH) in interstellar and cometary ice analogs by electron irradiation of carbon monoxide (CO) and methane (CH₄) mixture (Fig 7 and Fig 8) as well as carbon dioxide (CO₂) — ethylene (C₂H₄) mixtures. We also studied the formation of nitrous oxide (N₂O) which might be important the interstellar medium and on the surfaces Pluto and Triton (Fig 9). Nitrogen-oxides are also important as electron transfer molecules in biological processes.

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