Japan Geoscience Union Meeting 2022

Presentation information

[J] Oral

P (Space and Planetary Sciences ) » P-PS Planetary Sciences

[P-PS07] Planetary Sciences

Wed. May 25, 2022 9:00 AM - 10:30 AM Exhibition Hall Special Setting (1) (Exhibition Hall 8, Makuhari Messe)

convener:Hiroshi Kikuchi(Japan Aerospace Exploration Agency), convener:Masanori Kanamaru(Japan Aerospace Exploration Agency), Chairperson:Yuuya Nagaashi(Kobe University), Kenji Kurosaki(Department of Physics, Nagoya University)

9:45 AM - 10:00 AM

[PPS07-22] Space weathering simulation with UV irradiation on olivine

*Shinichi Morimitsu1, Sho Sasaki1, Hiroshi Kaiden2, Takahiro Hiroi3 (1.Department of Earth and Space Sciences, School of Science, Osaka University, 2.Department of Polar Science, 3.Department of Earth, Environmental and Planetary Sciences, Brown University)

Keywords:Space weathering, UV irradiattion, spectroscopy

Space weathering is the process to change in the optical properties of surface materials of air less rocky bodies, such as the moon and asteroids, due to prolonged exposure to space. The three typical changes in optical properties are reddening (increase in slope), darkening (overall darkening), and weakening of the absorption band in the reflection spectrum. These changes are thought to be caused by some changes in the minerals on the surface of celestial bodies due to micrometeorite impacts, solar wind irradiation, ultraviolet light from the sun, and cosmic rays.
Various laboratory experiments have been conducted to simulate these types of space weathering. However, although the effects of solar or ultraviolet radiation on space weathering have been suggested (Kaiden et al., 2019 LPSC No. 2132 2630.pdf), detailed results have not been obtained. In this study, we conducted a space weathering simulation experiment using an ultraviolet light lamp (Asahi Spectroscopic Co., Ltd. MAX-303, wavelength: 250~385 nm) to simulate ultraviolet light irradiation from the sun.
As a result of the experiment, a change in the darkening peculiar to space weathering effect was observed, where the spectral intensity in the visible region decreased by 30% due to UV light irradiation. In addition, no change in spectral intensity was observed in the infrared region, and reddening was also observed, where the slope of the entire spectrum became steeper. Furthermore, the olivine samples showed changes in a very short timescale, but the changes saturated quickly. This suggests that the UV-induced space weathering takes place in about ten days on the timescale of an astronomical object at 1 AU from the Sun.
From the above experiments, it was found that space weathering by UV irradiation proceeds in a very short timescale. Therefore, when conducting experiments with long timescales, such as those simulated by pulsed lasers, it would be possible to simulate the actual phenomenon by first giving the effect of space weathering by UV irradiation before conducting the experiments. However, what happens chemically on the olivine surface by UV irradiation needs to be studied in the future.