Infrared absorption spectroscopy of astronomically relevant reddish substances produced by cryoplasma irradiation of ice surface

Plasmas are applied to simulate energetic processes in space, and production and analysis of red organic materials, that show similar features to red organic materials observed in the outer solar system, have been reported. These organics could lead to understanding the origin of life and the formation process of the solar system. Recently a phenomenon, in which ice surface turns reddish only in cryogenic temperatures below 150 K, was observed in an experiment using cryoplasma [1]. This temperature dependence of coloration had not been reported in previous studies. However, the material, which is responsible for the reddish coloration, still needs to be investigated, e.g. for understanding its structure.

In this study, reddish coloration was produced by irradiating nitrogen-containing cryoplasma continuously for 12 hours at 85 K on methanol- and water-containing ice. In parallel, analysis of the ice was performed by infrared spectroscopy intermittently during 12 h. The infrared absorption spectra showed several absorption peaks that in part synchronized the coloration phenomena. Further details will be given in the conference.





[1] Sakakibara, N.; Yu, P. Y.; Ito, T.; Terashima, K. ApJL 2020, 891 (2), L44.