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[online] On Blue Ice: Antarctic Meteorites and Deepening Planetary Time - Alexis Rider, University of Pennsylvania
2020-06-04 14:00 - 15:00 UTC | Zoom
During the Antarctic field season of 1969, a group of Japanese glaciologists stumbled on a unique find—nine meteorite fragments, frozen and embedded in a patch of ancient blue ice. After geochemical analysis, the find was revealed to be even more surprising: rather than being pieces of one parent body, the meteorites were a collection of different rocks of varying terrestrial ages. Hearing of the Antarctic meteorites at a Conference four years later, geologist William Cassidy immediately suspected an explanation lay within the ice: slowly spreading from the center of the continent, the Antarctic ice sheet was a "stranding surface" that collected, subsumed, and finally revealed meteorites over a vast timeframe. Since then, the Antarctic Search for Meteorites program (ANSMET)—a joint venture between the NSF, the Smithsonian Institution, and NASA—has scoured patches of blue ice for the rare celestial objects, collecting as many as 6000 unique fragments in one field season.

This paper takes up Antarctic meteorites as natural chronometers, and traces how the space rocks gave glaciologists and meteoriticists a unique temporal tool for understanding the shape and flow of the Antarctic ice sheet. While meteoriticists were predominantly interested in the meteorites themselves—particularly after waning enthusiasm for moon landings—glaciologists focused on the ice in which they were encased: the preserved meteorites confirmed that blue ice was some of the oldest frozen matter on the planet, samples of which could be used to reconstruct past climates. This paper proposes that by treating meteorites and ice as relational timekeepers, rendered legible through similar modes of geochemical analysis, geologists and astrophysicists from the Smithsonian Astrophysical Observatory repositioned blue ice as a scientific tool, one that could connect the deep time of Antarctic ice to the deeper time of the cosmos.
