Nanobacteria are hypothetical, microscopic life-forms smaller than the smallest confirmed viruses or bacteria. Their possible existence was first suggested in 1989 when Robert H. Folk, a geologist at the University of Texas, Austin, discovered tiny spheres, only about 50 nanometers (nm) across, in mineral deposits from a hot-water spring in Viterbo, Italy. More recent investigations, by Folk and his colleague F. Leo Lynch, have turned up similar minuscule spheres in the sub-200-nanometer range, which microbiologists have argued is below the smallest possible size for a self-sustaining organism. Further evidence that biological entities may exist at this tiny scale have come from an Australian team and their claims concerning nanobes and the discovery of carbon balls, 30 to 150 nanometers across, in freshly opened pieces of the Allende meteorite.