Water in Interstellar Clouds Forms Around Dust Grains

Models of interstellar clouds show that it is unlikely for all of the water in them to have been produced by the combination of hydrogen gas and oxygen gas. Most of the water in interstellar clouds forms icy sheets around tiny grains of dust in these clouds. Akira Kouchi and colleagues at Hokkaido University in Sapporo, Japan have tested the theory that oxygen atoms accumulate on the grains and react with hydrogen to form water.

Kouchi’s team froze oxygen onto a nucleation surface held at 10 degrees above absolute zero.  They fired atoms of hydrogen onto the oxygen, creating hydrogen peroxide. The hydrogen peroxide then reacted with more hydrogen, producing water. The quick rate at which these reactions occurred explains the amount of water that is found in interstellar clouds. 

Paola Casselli at the University of Leeds has noted that the Kouchi’s team used oxygen molecules containing two oxygen atoms, but single oxygen atoms are more common in interstellar clouds.

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