In this paper we analyzed chromatograms and mass spectra of buckminsterfullerene and its isomers. We have calculated possible structures and formation energies of those isomers. We suppose that the most stable isomer which stability is comparable with that of C70 has the form close to a sphere. It has the symmetry axis of third order that passes through the centers of two hexagons, each of which being surrounded with three pentagons and three hexagons.