The surface of the Earth was a violent, hot mess 4.5 billion years ago. When life was still a distant possibility, temperatures could melt eyelids, and the air killed in seconds. The sun, too, was young — and bombarded the baby Earth with unkind bursts of radiation called flares and coronal mass ejections — which shot streams of highly-charged particles toward a planet already hostile to life.
In short, the young Earth was not a very nice place to live.
However, the now-extinct magnetic shield of the moon may have helped our little blue planet keep its atmosphere and eventually support and develop life in a habitable climate, according to a NASA-led study published in the journal Science Advances.
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