Ancient CluesĪbout 4.54 billion years ago, Earth was forming out of dust and rocks left over from the sun’s birth.
Taken together, the latest evidence from the ancient Earth and from the moon is painting a picture of a very different Hadean Earth: a stoutly solid, temperate, meteorite-clear and watery world, an Eden from the very beginning. It’s not completely out of the question that there would have been a habitable world and life of some kind,” said Elizabeth Bell, a geochemist at the University of California, Los Angeles.
There was water, potentially some stable crust. “Things were actually looking a lot more like the modern world, in some respects, early on. And instead of an epochal, final bombardment, meteorite strikes might have slowly tapered off as the solar system settled into its current configuration. Oxygen in those ancient rocks suggest the planet had water as far back as 4.3 billion years ago. The oldest rocks in the record suggest parts of the planet’s crust had cooled and solidified by 4.4 billion years ago. Many geologists now think Earth may have been tepid and watery from the outset. Not until a particularly violent asteroid barrage ended some 3.8 billion years ago could life have evolved.īut this story is increasingly under fire. The infant world would have been rent by volcanism and bombarded by other planetary crumbs, making for an environment so horrible, and so inhospitable to life, that the geologic era is named the Hadean, for the Greek underworld. But they all cast doubt on the traditional tale.Īs that story goes, in the half-billion years after it formed, Earth was hellish and hot. All of these microfossils - or the chemical evidence associated with them - are hotly debated. In the past year, separate teams of researchers have dug up, pulverized and laser-blasted pieces of rock that may contain life dating to 3.7, 3.95 and maybe even 4.28 billion years ago. The fossils add to a wave of discoveries that point to a new story of ancient Earth.
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