Igneous meteorites suggest Aluminium-26 heterogeneity in the early Solar Nebula

The short-lived radionuclide aluminium-26 (²⁶Al) isotope is a major heat source for early planetary melting. The aluminium-26 - magnesium-26 (²⁶Al-²⁶Mg) decay system also serves as a high-resolution relative chronometer. In both cases, however, it is critical to establish whether ²⁶Al was homogeneously or heterogeneously distributed throughout the solar nebula. Here we report a precise lead-207 - lead-206 (²⁰⁷Pb-²⁰⁶Pb) isotopic age of 4565.56 ± 0.12 million years (Ma) for the andesitic achondrite Erg Chech 002. Our analysis, in conjunction with published ²⁶Al-²⁶Mg data, reveals that the initial ²⁶Al/²⁷Al in the source material of this achondrite was notably higher than in various other well-preserved and precisely dated achondrites. Here we demonstrate that the current data clearly indicate spatial heterogeneity of ²⁶Al by a factor of 3-4 in the precursor molecular cloud or the protoplanetary disk of the Solar System, likely associated with the late infall of stellar materials with freshly synthesized radionuclides.