Greenland Rocks Suggest Earth's Magnetic Field is Older than We Thought

Alexandra Witze | Nature
Wednesday, December 11, 2019

Analysis by MIT EAPS Claire Nichols finds that the planet’s protective shield was in place by at least 3.7 billion years ago, as early life arose. Nature reports from AGU's Fall Meeting 2019.

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New research from MIT EAPS Claire Nichols finds that magnetic minerals (zircons) in ancient rocks from Greenland "suggest that Earth’s magnetic field arose at least 3.7 billion years ago," Alexandra Witze writes for Nature. "The work pushes back the estimate for the magnetic field’s birth by about 200 million years than the commonly accepted estimate — around the time when the first life appeared on Earth." Magnetic fields help protect atmospheres of planets and are thought to help make planets more hospitable to life, like Earth.

Nichols and her colleagues collected samples from an area that scientists think may contain fossils of complex life dating back 3.7 billion years.

Iron minerals in those rocks yielded information on the direction of Earth’s magnetic field when the minerals formed. Because the rocks are 3.7 billion years old, the magnetic signal must be too, Nichols said.

Her team ran various tests to try to be sure that the signal was real and not some sort of weak magnetism introduced later as the rocks were heated and squeezed.

Witze reports that results in area of research are a highly contested. While some scientists in attendence were skeptical of the result, most were keen to learn more.

Story Image: Earth's magnetic field, shown here as white lines, helps the planet hold onto its atmosphere. (Credit: Science Photo Library)