{"id":526972,"date":"2022-07-25T08:12:19","date_gmt":"2022-07-25T12:12:19","guid":{"rendered":"https:\/\/www.rochester.edu\/newscenter\/?p=526972"},"modified":"2022-08-08T13:43:20","modified_gmt":"2022-08-08T17:43:20","slug":"how-did-earth-avoid-mars-like-fate-ancient-rocks-hold-clues-526972","status":"publish","type":"post","link":"https:\/\/www.rochester.edu\/newscenter\/how-did-earth-avoid-mars-like-fate-ancient-rocks-hold-clues-526972\/","title":{"rendered":"How did Earth avoid a Mars-like fate? Ancient rocks hold clues"},"content":{"rendered":"
\"Three
A depiction of Earth, first without an inner core; second, with an inner core beginning to grow, around 550 million years ago; third, with an outermost and innermost inner core, around 450 million years ago. University of Rochester researchers used paleomagnetism to determine these two key dates in the history of the inner core, which they believe restored the planet\u2019s magnetic field just before the explosion of life on Earth.
(University of Rochester illustration \/ Michael Osadciw)<\/figcaption><\/figure>\n

New paleomagnetic research suggests Earth\u2019s solid inner core formed 550 million years ago and restored our planet\u2019s magnetic field.<\/h2>\n

Approximately 1,800 miles beneath our feet, swirling liquid iron in the Earth\u2019s outer core generates our planet\u2019s protective magnetic field. This magnetic field is invisible but is vital for life on Earth\u2019s surface because it shields the planet from solar wind\u2014streams of radiation from the sun.<\/p>\n

About 565 million years ago, however, the magnetic field\u2019s strength decreased to 10 percent of its strength today. Then, mysteriously, the field bounced back, regaining its strength just before the Cambrian explosion of multicellular life on Earth.<\/p>\n

What caused the magnetic field to bounce back?<\/p>\n

According to new research from scientists at the University of Rochester<\/a>, this rejuvenation happened within a few tens of millions of years\u2014rapid on geological timescales\u2014and coincided with the formation of Earth\u2019s solid inner core, suggesting that the core is likely a direct cause.<\/p>\n

\u201cThe inner core is tremendously important,\u201d says John Tarduno,<\/a> the William R. Kenan, Jr., Professor of Geophysics in the\u00a0Department of Earth and Environmental Sciences\u00a0<\/a>and dean of research for Arts, Sciences & Engineering at Rochester. \u201cRight before the inner core started to grow, the magnetic field was at the point of collapse, but as soon as the inner core started to grow, the field was regenerated.\u201d<\/p>\n

In the paper<\/a>, published in Nature Communications<\/em>, the researchers determined several key dates in the inner core\u2019s history, including a more precise estimate for its age. The research provides clues about the history and future evolution of Earth and how it became a habitable planet, as well as the evolution of other planets in the solar system.<\/p>\n

Unlocking information in ancient rocks<\/strong><\/h3>\n

Earth is composed of layers: the crust, where life is situated; the mantle, Earth\u2019s thickest layer; the molten outer core; and the solid inner core, which is, in turn, composed of an outermost inner core and an innermost inner core.<\/p>\n

Earth\u2019s magnetic field is generated in its outer core, where swirling liquid iron causes electric currents, driving a phenomenon called the geodynamo that produces the magnetic field.<\/p>\n

Because of the magnetic field\u2019s relationship to Earth\u2019s core, scientists have been trying for decades to determine how Earth\u2019s magnetic field and core have changed throughout our planet\u2019s history. They cannot directly measure the magnetic field due to the location and extreme temperatures of materials in the core. Fortunately, minerals that rise to Earth\u2019s surface contain tiny magnetic particles that lock in the direction and intensity of the magnetic field at the time the minerals cool from their molten state.<\/p>\n

To better constrain the age and growth of the inner core, Tarduno and his team used a CO2 laser and the lab\u2019s superconducting quantum interference device (SQUID) magnetometer to analyze feldspar crystals from the rock anorthosite. These crystals have minute magnetic needles within them that are \u201cperfect magnetic recorders,\u201d Tarduno says.<\/p>\n

By studying the magnetism locked in ancient crystals\u2014a field known as paleomagnetism\u2014the researchers determined two new important dates in the history of the inner core:<\/p>\n