Seeing the dawn

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Science  11 Jan 2019:
Vol. 363, Issue 6423, pp. 116-119
DOI: 10.1126/science.363.6423.116

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A cataclysm may have jump-started life on Earth. Some 4.47 billion years ago, a new scenario suggests—a mere 60 million years after Earth took shape and 20 million years after the moon formed—a moon-size object sideswiped Earth and exploded into an orbiting cloud of molten iron and other debris. The metallic hail that ensued likely produced a dense hydrogen atmosphere that, once things cooled down, could have kick-started the formation of simple organic molecules that went on to form more complex organic biomolecules such as RNA, long viewed as central to the life's emergence. This new scenario, along with other laboratory evidence, is offering a new view of life's dawn in Earth's earliest days.