Earth's Magnetic Field Is 3.5 Billion Years Old. Evidence for the existence of Earth’s magnetic field has been pushed back about 250 million years, new research suggests.
The field may therefore be old enough to have shielded some of the planet’s earliest life from the sun’s most harmful cosmic radiation. Earth’s magnetic field was born by 3.45 billion years ago, a team including researchers from the University of Rochester in New York and the University of KwaZulu-Natal in South Africa report in the March 5 issue of Science. That date falls during life’s earliest stages of development, between the period when the Earth was pummeled by interplanetary debris and when the atmosphere filled with oxygen. Several earlier studies had suggested that a magnetic field is a necessary shield against deadly solar radiation that can strip away a planet’s atmosphere, evaporate water and snuff out life on its surface.
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