[P-PS07] Planetary Sciences

[PPS07-P11] Space weathering of C-type asteroids simulated by UV irradiation

*Yusuke Egashira¹, Sho Sasaki¹, Hikaru Yabuta², ERI TATSUMI³, Hiroshi Kaiden⁴, Takahiro Hiroi⁵, Shinichi Morimitsu¹ (1.Department of Earth and Space Sciences, School of Science, Osaka University, 2.Hiroshima University, Department of Earth and Planetary Systems Science, 3.Instituto de Astrofisica de Canarias, 4.Department of Polar Science, 5.Department of Earth, Environmental and Planetary Sciences, Brown University)

Keywords:Space weathering, UV irradiation, C-type asteroids

Space weathering is the process where the optical properties of an airless body's surface change due to prolonged exposure to space. Since the measurement of reflectance spectra is commonly used to determine the surface materials of bodies, space weathering, which alters the spectra, is a significant influence on material identification. It is also expected that the degree of change in the spectra will help to determine the age of the surface of the body. In the case of the Moon and S-type asteroids, it is known that the following changes occur: an increase in the slope of the spectra (reddening), a decrease in reflectance (darkening), and a weakening of the absorption bands. Space weathering of C-type asteroids has also been studied using ion irradiation to simulate solar wind and laser irradiation to simulate micrometeorite impacts. However, in some cases, bluing and brightening, which are the opposite changes of reddening and darkening, occur, and no clear conclusion has been reached as to the cause of these phenomena. In addition, few researches have been conducted on space weathering simulated by ultraviolet irradiation.
In this study, we simulated space weathering on a C-type asteroid by ultraviolet irradiation from the sun using an UV lamp. Three carbonaceous chondrites (Aguas Zarcas, Murchison, and Jbilet Winselwan) and two coal samples (DECS3 and DECS7) were used as samples. Experimental results showed that the spectra varied, and the trends of increasing or decreasing slope and reflectance varied from sample to sample. This suggests that UV is a cause of space weathering in C-type asteroids. Factors contributing to the spectral changes will also be discussed.