Serpentine nanotubes in the Mighei CM chondrite

We report the discovery of serpentine nanotubes in the Mighei CM chondrite. High-resolution transmission electron microscope (HRTEM) images show that the nanotubes are multiwalled, containing from 3 to 11 layers with periodicities of 0.68±0.08 nm. Some nanotubes appear capped. Their lengths and inner diameters range from 20 to 230 nm and 2 to 9 nm, respectively, with internal volumes of 200–11,300 nm3. Chemical analyses made using electron energy-loss spectroscopy (EELS) give Mg1.7Fe0.52+Fe0.73+[Si1.5Fe0.53+O5]H1.8([]1.0O2.4S0.6)∑=4, with H determined by difference. The S-bearing and Fe-rich composition of these nanotubes is distinct from previously reported meteoritic and terrestrial materials, and we believe them to be a new variety of serpentine. These intriguing structures likely formed during aqueous-alteration events early in the history of the solar system and potentially served as containers of primordial fluids.