Komaki        35°18’38"N, 136°56’59"E

Chubu, Japan

Confirmed fall: 2018 Sep 26

Classification: Ordinary chondrite (L6)

History: Around 22:30 on September 26, 2018, a detonating sound was heard at a private house in Komatsuji, Komaki city, Aichi prefecture, Japan. No fireball was observed because of the cloudy weather, with intermittent rain. Next morning, several fragments including 81 g and 23 g were found on the roof and in the garden. A 550 g mass was also found at the next-door house. The meteorite apparently hit the roof, bounced to the next house, penetrated the roof of the carport, and hit the roof of the car. It finally came to rest in front of the entrance door. The meteorite was brought to NMNS on October 6, where cosmogenic Na-22 and Al-26 gamma rays were detected by the pure Ge detector.

Physical characteristics: The 550 g mass is a rounded disk shape. One side is fully covered by fusion crust and the other is about half covered. The 81 g and 23 g fragments fit together with the 550 g mass, hence the meteorite was one mass that fragmented due to the impact on the roof.

Petrography: A polished thin section and a polished mount were made from a 1 g fragment at NIPR. Olivine compositions are Fa_23.9-25.5 (mean Fa_24.7, N=31), and low-Ca pyroxene compositions are Fs_20.0-21.3 (mean Fs_20.7, N=19). The presence of plagioclase >50 μm indicates that the petrologic type is 6. The presence of mottled extinction and planar fractures in olivine indicates that the shock stage is S3.

Geochemistry: Using a 50 mg fragment, rare gas analyses were made at KyuU. The Ne-21 cosmic-ray exposure age is 25.1±0.6 Ma, and the K-Ar gas retension age is 4.4±0.2 Ga.

Classification: L6

Specimens: NMNS: 81 g for display, 20 g for type specimen; NIPR: 1 polished thin section, 1 polished mount