Water is an important oxygen reservoir in space and is often used as a tracer of large-scale gas-phase dynamics in star forming regions. Moreover, it is a crucial molecule for the existence of life on Earth. To date, the exact mechanisms leading to both water formation in space and its delivery to Earth are not fully understood.In 1982, Tielens and Hagen suggested low-temperature surface chemistry on icy dust grains as the main water formation route in dense molecular clouds. Furthermore, deuterated water, specifically HDO, has recently been suggested to play an important role in the understanding of the origin of water on Earth (Morbidelli et al. 2000). In the past decade, several independent laboratories performed systematic studies of specific reaction routes leading to water formation under interstellar relevant conditions: H/H2 + O/O2/O3 (e.g., Miyauchi et al. 2008, Matar et al. 2008, Ioppolo et al. 2008, 2010, Cuppen et al. 2010, Romanzin et al. 2011, Lamberts et al. 2013). Here, I will present an overview of the specific reaction routes within the full astrochemical reaction network leading to the surface formation of water ice. Particular attention is paid to the work performed with SURFRESIDE in Leiden. The reactants, i.e., atoms and molecules, are deposited on a gold substrate at temperatures ranging between 13 K and 150 K. On the cold surface, reactants can diffuse and react. Sequential deposition and co-deposition experiments are used to investigate intermediate (HO2 and OH) and final reaction products (H2O2 and H2O). The specific case of H2 + O, a surface reaction not fully investigated in the laboratory, is discussed in detail. Finally, I will show the importance of studying single reaction channels for the example of HDO formation, both at low (15 K) and high (145 K) temperatures.

Surface formation of water in interstellar ice analogs

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.