Mineralogy of terminal grains recovered from the Tanpopo capture panel onboard the International Space Station

Abstract The Tanpopo experiment is Japan's first astrobiology mission aboard the Japanese Experiment Module Exposed Facility on the International Space Station. The Tanpopo‐1 mission exposed silica aerogel panels to low Earth orbit from 2015 to 2016 to capture micrometeoroids. We identified an impact track measuring approximately 8 mm long, which contained terminal grains in the silica aerogel panel oriented toward space. The impact track exhibited a bulbous cavity with two thin, straight tracks branching from it, each preserving a terminal grain at their ends. The terminal grains were extracted from the silica aerogel and analyzed using scanning transmission electron microscopy and scanning transmission X‐ray microscopy to investigate their X‐ray absorption near‐edge structure (STXM‐XANES). Both grains are Fe‐bearing and relatively homogeneous orthopyroxene crystals (En 88.4±0.4 and En 88.2±1.8 ). The recovery of Fe‐bearing low‐Ca pyroxene aligns with previous studies of micrometeoroids captured in LEO. Micrometeoroids containing Fe‐bearing olivine and low‐Ca pyroxene are likely abundant in LEO.