In the Solar System's first million years, before any planet had taken shape, the cosmos was already exercising a kind of preference — reaching for heat-forged rocky spheres called chondrules and setting aside the cold, icy dust that would later play a larger role in planetary assembly. Yale-led researchers, working backward through the chemistry of ancient iron meteorites, have found that the earliest solid bodies were composed of 83 to 92 percent chondrules, with water-rich matrix material making up a mere fraction of the whole. The discovery pushes the evidence for selective planet-building