MS-2-P-2938 HRTEM studies of Bamboo-like nanotubes found in the carbonaceous chondrite Allende meteorite.

In February 8, 1969 a large carbonaceous chondrite meteorite fell in Allende Chihuahua, Mexico. Carbonaceous chondrites meteorites are very important because of their organic compounds and peculiar composition. Allende meteorite has large and abundant chondrules (mm-sized) in olivine matrix, large refractory inclusions, a low degree of aqueous alteration and graphitized carbon. Its large carbon content has represented an interesting source to the study of evolution and lineage of carbon chemistry, from nebular to current ages and has been related with prebiotic Earth, because its collisions and impacts with early Earth formation represent an organics extraterrestrial input. The organic composition in carbonaceous chondrites is diverse, and it is possible to mention as example kerogenic material macromolecular, sugar alcohols, ketones, amines, and amino acids. The nanostructures in this type of meteorites have been identified as fullerenes, carbon onions and the possible presence of carbon nanotubes (CNTs) has been suggested since 2006. Actually, inorganic serpentine nanotubes were described by Zega and co-workers in meteoritic matrix of carbonaceous chondrites, ranking in ~20nm diameter tube.

At high temperatures, carbon precursors are decomposed or evaporated and then condensed to build the sp2 graphite networks of CNTs. High temperatures are normally obtained from external heating, which is highly energy-consumed. Theoretically, such a problem can be solved by employing hugely exothermic reaction systems like the conditions of the early sun.

The sample was obtained from the collection of the Geology Institute, at the Autonomous National University of Mexico. In order to avoid the contamination of the meteorite sample, we drilled a hole with a steel laboratory spatula in the small piece of the meteorite. The powder obtained was supported in a microscopy glass slide and grinded with a second slide. The powder was supported in an electron microscopy grid to be observed in a JEM-2200FS TEM.
By HRTEM we observed bamboo-carbon nanotubes (BCNTs) in the meteorite sample as well as polyhedrical carbon structures. BCNTs can be thought as coaxial graphene sheets built of sp2 bonded. The tubes are concentric and coaxial. They also are highly defective and several bounds are broken, this fact promotes active bonds to act as chiral templates of other organic molecules.