Chiral biases in solids by effect of shear gradients: a speculation on the deterministic origin of biological homochirality.

We present an experimental approach to the study of the chirality of three CM2 meteorite solid samples by direct measurement of the optical activity (circular birefringence; CB). The measurements are based on transmission two modulator generalized ellipsometry in conjuction with microscope optics to map the CB of the samples. In spite of the complexity of such optical analysis, these first results indicate the presence of optically active areas in the meteorite solid matrix. In the case of the Murchison sample the statistics of the CB mapping shows a bimodal distribution with a bias to negative CB values. The composition of the active areas probably corresponds to serpentines and other poorly identified phyllosilicate phases. The results are compatible with the hypothesis that in a mineral-based scenario for the origin of life a CB sign bias in the chiral fractures originated by mechanical and flow shear gradients on clays could be later transferred to the reactions of the absorbed organic compounds.