Earth’s oxygen levels rose and fell more than once hundreds of millions of years before the planetwide success of the Great Oxidation Event about 2.4 billion years ago, new research from the University of Washington shows.

The evidence comes from a new study that indicates a second and much earlier “whiff” of oxygen in Earth’s distant past — in the atmosphere and on the surface of a large stretch of ocean — showing that the oxygenation of the Earth was a complex process of repeated trying and failing over a vast stretch of time.

The finding also may have implications in the search for life beyond Earth. Coming years will bring powerful new ground- and space-based telescopes able to analyze the atmospheres of distant planets. This work could help keep astronomers from unduly ruling out “false negatives,” or inhabited planets that may not at first appear to be so due to undetectable oxygen levels.

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The study, “Transient surface ocean oxygenation recorded in the ∼2.66-Ga Jeerinah Formation, Australia,” was published in the journal Proceedings of the National Academy of Science of the United States (PNAS). The work was supported by NASA Astrobiology through the Exobiology Program.