The first 700 million years of Earth’s 4.5-billion-year existence are known as the Hadean period, after Hades, or, to shed the ancient Greek name, Hell.

That is no longer thought to be true.

Over the last decade, the mineralogical analysis of small hardy crystals known as zircons embedded in old Australian rocks has painted a picture of the Hadean period “completely inconsistent with this myth we made up,” Dr. Harrison said.

“The picture that’s emerging is a watery world with normal rock recycling processes,” said Stephen J. Mojzsis, a professor of geology at the University of Colorado who was not involved with the U.C.L.A. research. “And that’s a comforting thought for the origin of life.”