TY - JOUR
T1 - Measurement of Microscopic Thermal Diffusivity Distribution for Ryugu Sample by Infrared Lock-in Periodic Heating Method
AU - Ishizaki, Takuya
AU - Nagano, Hosei
AU - Tanaka, Satoshi
AU - Sakatani, Naoya
AU - Nakamura, Tomoki
AU - Okada, Tatsuaki
AU - Fujita, Ryohei
AU - Alasli, Abdulkareem
AU - Morita, Tomoyo
AU - Kikuiri, Mizuha
AU - Amano, Kana
AU - Kagawa, Eiichi
AU - Yurimoto, Hisayoshi
AU - Noguchi, Takaaki
AU - Okazaki, Ryuji
AU - Yabuta, Hikaru
AU - Naraoka, Hiroshi
AU - Sakamoto, Kanako
AU - Tachibana, Shogo
AU - Watanabe, Sei ichiro
AU - Tsuda, Yuichi
N1 - Publisher Copyright:
© 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
PY - 2023/4
Y1 - 2023/4
N2 - The thermophysical properties of small Solar System bodies are essential to be determined, on which the thermal evolution of small bodies largely depends. The carbonaceous asteroid Ryugu is one of the small undifferentiated bodies formed in the early Solar System. Hayabusa2 explored the asteroid Ryugu and returned the surface samples in 2020 for detailed on-ground investigation, including measurements of thermal properties. Because the available sample amount was limited, this study developed a novel method to measure the thermal diffusivity of small and irregularly shaped samples of about 1 mm in diameter by combining lock-in thermography and periodic heating methods on the microscale. This method enables us to measure the thermal diffusivity of both flat-plate and granular shape samples by selecting the suitable detecting direction of the temperature response. Especially, when the sample has a flat-plate shape, the anisotropic distribution of the in-plane thermal diffusivity can be evaluated. This method was applied to six Ryugu samples, and the detailed anisotropic distribution of the thermal diffusivity was obtained. The measurement results showed that the samples show local thermal anisotropy caused by cracks and voids. The average thermal diffusivity among all samples was (2.8 to 5.8) × 10−7 m2·s. Based on the density and specific heat of the samples obtained independently, the thermal effusivity was estimated to be 791 J·(s1/2·m2·K) to 1253 J·(s1/2·m2·K), which is defined as the resistance of surface temperature to the change of thermal input. The determined thermal effusivity, often called thermal inertia in planetary science, is larger than the observed value of 225 ± 45 J· (s1/2·m2·K) of the asteroid Ryugu's surface, obtained from the diurnal temperature change of the rotating asteroid by a thermal infrared camera onboard Hayabuas2. This difference is likely to be attributed to the difference in the analytical scale between the sample and the surface boulders compared with the thermal diffusion length. Consequently, it was found that the present result is more representative of the thermal diffusivity and thermal inertia of local part of individual Ryugu particles.
AB - The thermophysical properties of small Solar System bodies are essential to be determined, on which the thermal evolution of small bodies largely depends. The carbonaceous asteroid Ryugu is one of the small undifferentiated bodies formed in the early Solar System. Hayabusa2 explored the asteroid Ryugu and returned the surface samples in 2020 for detailed on-ground investigation, including measurements of thermal properties. Because the available sample amount was limited, this study developed a novel method to measure the thermal diffusivity of small and irregularly shaped samples of about 1 mm in diameter by combining lock-in thermography and periodic heating methods on the microscale. This method enables us to measure the thermal diffusivity of both flat-plate and granular shape samples by selecting the suitable detecting direction of the temperature response. Especially, when the sample has a flat-plate shape, the anisotropic distribution of the in-plane thermal diffusivity can be evaluated. This method was applied to six Ryugu samples, and the detailed anisotropic distribution of the thermal diffusivity was obtained. The measurement results showed that the samples show local thermal anisotropy caused by cracks and voids. The average thermal diffusivity among all samples was (2.8 to 5.8) × 10−7 m2·s. Based on the density and specific heat of the samples obtained independently, the thermal effusivity was estimated to be 791 J·(s1/2·m2·K) to 1253 J·(s1/2·m2·K), which is defined as the resistance of surface temperature to the change of thermal input. The determined thermal effusivity, often called thermal inertia in planetary science, is larger than the observed value of 225 ± 45 J· (s1/2·m2·K) of the asteroid Ryugu's surface, obtained from the diurnal temperature change of the rotating asteroid by a thermal infrared camera onboard Hayabuas2. This difference is likely to be attributed to the difference in the analytical scale between the sample and the surface boulders compared with the thermal diffusion length. Consequently, it was found that the present result is more representative of the thermal diffusivity and thermal inertia of local part of individual Ryugu particles.
KW - Asteroid
KW - Distribution
KW - Measurement method
KW - Microscale
KW - Non-contact
KW - Ryugu
KW - Thermal diffusivity
KW - Thermal effusivity
KW - Thermal inertia
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U2 - 10.1007/s10765-023-03158-6
DO - 10.1007/s10765-023-03158-6
M3 - Article
AN - SCOPUS:85147928920
SN - 0195-928X
VL - 44
JO - International Journal of Thermophysics
JF - International Journal of Thermophysics
IS - 4
M1 - 51
ER -