Origin of H2O gases in interstellar molecular clouds at low temperatures: Does H2O desorb from CO-H2O ice?

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14534
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17010:Space and planetary sciences-related
• Research Institution: National Institute of Science and Technology Policy (2021-2022); Hokkaido University (2020)
• Principal Investigator: Kitajima Kensei 文部科学省科学技術・学術政策研究所, 第2研究グループ, 研究員 (70845445)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 氷 / 光脱離 / 水分子 / 星間分子雲 / 星間塵表面

Outline of Final Research Achievements

To understand the origin of H2O gas in interstellar molecular clouds, it is important to understand the H2O desorption process on the surface of ice particles (icy dust grains) in molecular clouds. In this study, we investigated whether H2O molecules from low-temperature H2O ice the top of which is covered with CO solid can be desorbed by photodesorption. We experimentally prepared a bilayer of CO and H2O ice (CO-H2O ice) and detected the desorbed H2O using photo-stimulated desorption and resonant multiphoton ionization (PSD-REMPI) techniques. The H2O signal was monitored by changing the thickness of the CO solid coverage, and it was found that the H2O signal decreased gradually, but H2O was still detected even when the ice was covered with several tens of monolayers of CO.

Free Research Field

宇宙惑星科学

Academic Significance and Societal Importance of the Research Achievements

星間塵を覆う極低温のCO固体はポーラスな構造を持ちうるため，その下層にH2Oが存在する場合，空隙を通じてこれら分子が脱離する可能性がある．本研究では，上層が数10分子層のCOで覆われたCO-H2Oの二層氷においてH2Oが光脱離しうる結果が示され，分子雲中におけるH2Oガス起源の解明に資する知見が得られた．