Ancient Rocks Hold Clues to How Earth Avoided Fate Like Mars
Depiction of Earth, first without an inner core; second, with a growing inner core, about 550 million years ago; third, with the outermost and innermost core, about 450 million years ago. University of Rochester researchers used paleomagnetism to determine these two important dates in the history of the inner core, which they believe restored the planet’s magnetic field just before the explosion of life on Earth. Credit: University of Rochester Illustration / Michael Osadciw New paleomagnetic research shows Earth’s dense core formed 550 million years ago and restored our planet’s magnetic field. The rotating molten iron in Earth’s outer core, which lies about 1,800 miles below our feet, produces our planet’s protective magnetic field, called the magnetosphere. Although this magnetic field is invisible, it is essential for life on Earth’s surface. That’s because the magnetosphere protects the planet from the solar wind—the stream of radiation from the sun. However, about 565 milli