Yamato 691 in captivity (Courtesy Akira Yamaguchi, NIPR, Tachikawa, Tokyo, Japan).
The 2019-2020 ANSMET field season corresponds to several anniversaries that we find significant, but none more important than today. Fifty years ago, on December 21, 1969, Renji Naruse of the 10th Japanese Antarctic Research Expedition (JARE-10) was one of several glaciologists embedding a network of survey stations in the East Antarctic ice sheet to allow the study of glacial movement. As they extended their survey across a blue icefield uphill from the Yamato (Queen Fabiola) Mountains, they found the first of a total of nine meteorite specimens the group would discover that season. The specimens were returned to Masao Gorai, an igneous petrologist and member of the Special Committee on Antarctic Research, Science Council of Japan. Before the field season, Gorai had requested that the party recover “a meteorite or some weird stuff” since he was no longer interested in the more accessible rocks found close to Japan’s Syowa Station. Following the field work Gorai was presented with the nine specimens, and his initial analysis revealed that they included E, H and L chondrites, a diogenite, and a carbonaceous chondrite, thus representing at least 5 distinct petrographic groups.
The implication of a possible concentration mechanism was immediately recognized by the Japanese. Yoshida et al. (1971) noted two important things. First, they noted that the discovery of several different petrologic types in close proximity to each other “… is a matter of particular interest”. Second, they noted “the movement and structure of (the) ice sheet of the area may account for the concentration of the meteorites”. From these observations they concluded that “there may be some other areas … having a possibility of concentration of meteorites”.
These implications were not immediately grasped outside of Japan – those who heard of the Yamato finds generally assumed that they were nine fragments of a shower fall, or did not look beyond the novelty represented by these specimens. But at least one person in the west took notice. A presentation concerning the mineralogy of the 1969 Yamato meteorites at the 1973 meeting of the Meteoritical Society (Shima and Shima, 1973) provided William Cassidy of the University of Pittsburgh with a “Eureka!” moment; he recognized that these specimens were the vanguard of a potentially huge number of meteorites. Cassidy enthusiastically shared his insight with others, and proposed a US supported search in the Transantarctic Mountains area. While his first few proposals were turned down, the mounting number of meteorite recoveries by the Japanese eventually convinced the United States Antarctic Research Program (now USAP) to begin searches in the 1976-77 field season. ANSMET was born, and as of this writing is poised to begin its 43rd season.
-an expanded version can be found in this old paper. Required reading, IMHO (rph).
References
Yoshida M, Ando H, Omoto K, Naruse R, Ageta Y (1971) Discovery of meteorites near Yamato Mountains, East Antarctica. Japanese Antarctic Record 39, 62–65.
Gorai M (1970) Meteorite “Museum” in the Antarctic. Magma 23, p. 8 (translated from the Japanese by Gen Hashimoto; provided to the author by Ursula Marvin).
Shima M, Shima M (1973) Mineralogical and chemical composition of new Antarctica meteorites. Meteoritics 8, 439–440.