Did the Terrestrial Planets Form by Pebble Accretion?

The study by Alessandro Morbidelli and colleagues evaluates two theories of terrestrial planet formation: the classical model and pebble accretion. The classical model, involving collisions and mergers of planetesimals, aligns better with observed isotopic compositions, volatile element patterns, and planetary dynamics. In contrast, pebble accretion, which predicts significant contributions of carbonaceous material and rapid formation within the gas disk's lifetime, is inconsistent with the data. The researchers conclude that while pebbles may have contributed early in planetary growth, the formation of Earth and its neighbors was dominated by the classical model of planetesimal collisions and giant impacts.