At a microscopic level, spheres are found in the meteorite that are rich in carbon compared to surrounding areas that lack such spheres. The carbon-rich spheres and the observed micro-tunnels may have been formed by biotic activity, according to NASA scientists.
The mass of the meteorite is 13.7 kg (30 lb). It is an unbrecciated cumulus igneous rock consisting predominantly of elongated augite crystals —a solid solution in the pyroxene group. Japanese scientists from the National Institute of Polar Research reported in 2003 that the meteorite contains iddingsite, which forms from the weathering of basalt in the presence of liquid water. In addition, NASA researchers reported in February 2014 that they also found carbon-rich spheres encased in multiple layers of iddingsite, as well as microtubular features emanating from iddingsite veins displaying curved, undulating shapes consistent with bio-alteration textures observed in terrestrial basaltic glass. However, the scientific consensus is that "morphology alone cannot be used unambiguously as a tool for primitive life detection." Interpretation of morphology is notoriously subjective, and its use alone has led to numerous errors of interpretation. According to the NASA team, the presence of carbon and lack of corresponding cations is consistent with the occurrence of organic matter embedded in iddingsite. The NASA researchers indicated that mass spectrometry may provide deeper insight into the nature of the carbon, and could distinguish between abiotic and biologic carbon incorporation and alteration.
^Mikouchi, T.; E. Koizumi, A. Monkawa, Y. Ueda (March 2003). "Mineralogy and petrology of Yamato 000593: Comparison with other Martian nakhlite meteorites". Antarctic meteorite research16: 34–57.Cite uses deprecated parameters (help);|accessdate= requires |url= (help)