Scientists have discovered extremely rare remnants of “proto Earth,” which formed about 4.5 billion years ago, before a colossal impact irreversibly altered the primitive planet’s composition and produced Earth as we know today. Their findings will help scientists piece together the primordial starting ingredients that forged early Earth and the solar system.
Is it reasonable to call one of the two planets before the impact, Earth? I’d argue the two planets mixed together formed Earth (and the Moon).