Sunday, August 14, 2022

How can Earth escape a fate like Mars? Ancient rocks contain clues

Depiction of Earth, first without inner core; second, with the inner core growing out about 550 million years ago; Third, about 450 million years ago with a deep outer and inner core. Researchers at the University of Rochester used paleomagnetism to determine these two important dates in the history of the inner core, which they believe restored the planet’s magnetic field before the explosion of life on Earth. credit: University of Rochester/Michael Osadio

Our planet’s protective magnetic field is generated by the swirling of molten iron in Earth’s outer core, about 1,800 miles below our feet. This magnetic field is invisible but essential to life on Earth because it protects the planet from the solar wind – the flux of radiation from the Sun.

However, about 565 million years ago, the strength of the force field dropped to 10 percent of today’s strength. Then, mysteriously, the field bounced back, regaining its strength before the Cambrian explosion of multicellular life on Earth.

What is the reason for the surge of magnetic field?

According to new research by University of Rochester scientists, this uplift occurred within a few tens of millions of years – over a rapid geologic chronology – and coincided with the formation of Earth’s dense core, suggesting that the core may be the direct cause. could. ,

“The inner core is very important,” said John Tarduno, professor of geophysics in the Department of Earth and Environmental Sciences and dean of arts, science and engineering research at Rochester. “Just before the inner core grew, the magnetic field nearly collapsed, but once the inner core began to grow, the field renewed.”

in a paper published in natural connectionIn this article, researchers identify several important dates in the history of the deep core, including a more accurate estimate of its age. The research provides clues about the future history and evolution of Earth and how it became a habitable planet, as well as the evolution of other planets in the Solar System.

Unlock information in ancient rocks

Earth is made up of layers: the crust where life exists; That is the mantle, the thickest layer on Earth; The outer core is liquid and the inner core is solid, which in turn has an outer inner core and a dark inner core.

Earth’s magnetic field is created in its outer core, which causes the molten iron to spin with an electric current. It drives a phenomenon called geodynamo which generates a magnetic field.

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Because of the magnetic field’s connection to Earth’s center, scientists have been trying for decades to determine how the magnetic field and Earth’s core have changed throughout the history of our planet. They cannot directly measure the magnetic field due to the location of the material in the core and the extreme temperatures. Fortunately, minerals that rise to Earth’s surface contain tiny magnetic particles that lock into the direction and intensity of the magnetic field as the mineral cools from its molten state.

To further limit the lifetime and growth of the inner core, Tarduno and his team used carbon dioxide2 In vitro laser and superconducting quantum interference device (SQUID) for analyzing feldspar crystals from anorthosite rocks. Tarduno said the crystal consists of a tiny magnetic needle, inside which is an “ideal magnetic recorder.”

By studying magnets trapped in ancient crystals – a field known as palaeomagnetism – researchers have identified two important new dates in the history of the deep nucleus:

  • 550 million years ago: The time when the magnetic field began to regenerate rapidly after a collapse, about 15 million years ago. The researchers attribute the rapid regeneration of the magnetic field to the creation of a hardened inner steel that recharges the molten outer core and restores magnetic field strength.
  • 450 million years ago: The time when the structure of the growing inner nucleus changes, indicating the boundary between the inner and outer nuclei. Due to plate tectonics on the roof, these changes in the inner core coincide with changes in the structure of the top shelf at roughly the same time.

“Since we defined the age of the inner core more precisely, we were able to infer the fact that the current inner core actually consists of two parts,” Tarduno said. “The movement of tectonic plates on Earth’s surface indirectly affects the inner core, and the history of this movement is inscribed deep within Earth in the structure of the inner core.”

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Avoid luck like Mars

A better understanding of the dynamics and evolution of the inner core and magnetic field will have important implications in uncovering not only Earth’s past and predicting its future, but also the ways in which other planets can create and harbor magnetic shields. can maintain the conditions necessary for life.

Researchers believe that Mars, for example, once had a magnetic field, but that field disappeared, leaving the planet vulnerable to it. Solar wind and no ocean surface. While it is not clear whether Earth would suffer the same fate due to the absence of a magnetic field, “Earth would have lost a lot of water.” If Earth’s magnetic field was not renewed, the planet would become dry and it would will be very different. Today’s planets,” Tarduno said.

With regard to planetary evolution, the research underscores the importance of magnetic shielding and its protection mechanisms, he said.

“This research really highlights the need to develop something like an inner core that sustains the magnetic field for life — several billion years — of a planet.”


New research provides evidence of a strong early magnetic field around Earth


further information:

Tinghong Zhou et al, Early Cambrian Refurbishment of Geodynamo and Origin of Internal Infrastructure, natural connection (2022). DOI: 10.1038/s41467-022-31677-7

introduction
University of Rochester

Citation How can Earth escape a fate like Mars? Ancient rocks containing clues (2022, July 25) Retrieved on 26 July 2022 from https://phys.org/news/2022-07-earth-mars-like-fate-ancient-clues.html.

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