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Science missions to comets and moons in our solar system have returned surprising results about the presence and abundance of small molecules, such as H2, O2, CH3OH, and even Glycine, whose formation in the extreme conditions of outer space is puzzling. Such molecules are considered biomarkers and may relate to the origin of life and water on Earth. This talk will explore new and unusual reaction dynamics of energetic H2O molecules colliding with surfaces of astrophysical relevance, where reaction barriers are overcome by kinetic energy. Three such reactions will be discussed: (i) the splitting of water directly into molecular H2 and atomic oxygen in single collisions of water ions with generic surfaces, (ii) the abstraction of oxygen from oxidized surfaces by water ions, which leads to facile production of molecular O2 and (iii) the dynamic deuterium exchange in normal water ion collisions with deuterated surfaces. The former two reactions offer abiotic explanations for the origin of the H2 discovered recently on Enceladus, and the O2 found in abundance on comet 67P. The last reaction suggests a possible way to alter the D/H ratio in water when detected in situ in cometary comae. The findings have broad implications for measurements of gas-phase composition in astrophysical environments. |
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