Microstructure and elemental composition of the Tagish Lake meteorite and its astrobiological implications

Abstract

AbstractTagish Lake meteorite, which fell in January 2000 in Canada, has provided a sample of pristine cosmic materials for laboratory studies. It is made up of loosely formed aggregates, making it one of the most friable carbonaceous chondrites. Its complex structure is composed of plaquettes of crystalized minerals, hexagon-shaped metals, chondrules and granules, all of which are embedded in a matrix of fine grains and fibril-like materials. Those components with sizes larger than 250 nm in diameter are affected to varying degrees by hydrothermal reactions, whereas the majority of smaller bodies (<350 nm in diameter) appear unscathed despite severe aqueous alterations on the parent body. A high population of granules (100–300 nm in diameter) consist of a wall (20–40 nm in thickness) and a larger core; the former is rich in organic elements, such as carbon, oxygen and sulfur, and the core contains Ni-Fe-Mg rich silicates. The organic matter has aromatic and aliphatic characteristics, and such evidence suggests that the granules may be the carriers of large organic species with distinct astrobiological implications.