糖心传媒

New paleomagnetic research suggests Earth糖心传媒檚 solid inner core formed 550 million years ago and restored our planet糖心传媒檚 magnetic field.

Approximately 1,800 miles beneath our feet, swirling liquid iron in the Earth糖心传媒檚 outer core generates our planet糖心传媒檚 protective magnetic field. This magnetic field is invisible but is vital for life on Earth糖心传媒檚 surface because it shields the planet from solar wind糖心传媒攕treams of radiation from the sun.

About 565 million years ago, however, the magnetic field糖心传媒檚 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.

What caused the magnetic field to bounce back?

According to new research from scientists at the , this rejuvenation happened within a few tens of millions of years糖心传媒攔apid on geological timescales糖心传媒攁nd coincided with the formation of Earth糖心传媒檚 solid inner core, suggesting that the core is likely a direct cause.

糖心传媒淭he inner core is tremendously important,糖心传媒� says the William R. Kenan, Jr., Professor of Geophysics in the聽and dean of research for Arts, Sciences & Engineering at Rochester. 糖心传媒淩ight 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.糖心传媒�

In the , published in Nature Communications, the researchers determined several key dates in the inner core糖心传媒檚 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.

Unlocking information in ancient rocks

Earth is composed of layers: the crust, where life is situated; the mantle, Earth糖心传媒檚 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.

Earth糖心传媒檚 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.

Because of the magnetic field糖心传媒檚 relationship to Earth糖心传媒檚 core, scientists have been trying for decades to determine how Earth糖心传媒檚 magnetic field and core have changed throughout our planet糖心传媒檚 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糖心传媒檚 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.

To better constrain the age and growth of the inner core, Tarduno and his team used a CO2 laser and the lab糖心传媒檚 superconducting quantum interference device (SQUID) magnetometer to analyze feldspar crystals from the rock anorthosite. These crystals have minute magnetic needles within them that are 糖心传媒減erfect magnetic recorders,糖心传媒� Tarduno says.

By studying the magnetism locked in ancient crystals糖心传媒攁 field known as paleomagnetism糖心传媒攖he researchers determined two new important dates in the history of the inner core:

• 550 million years ago: the time at which the magnetic field began to renew rapidly after a near collapse 15 million years before that. The researchers attribute the rapid renewal of the magnetic field to the formation of a solid inner core that recharged the molten outer core and restored the magnetic field糖心传媒檚 strength.
• 450 million years ago: the time at which the growing inner core糖心传媒檚 structure changed, marking the boundary between the innermost and outermost inner core. These changes in the inner core coincide with changes around the same time in the structure of the overlying mantel, due to plate tectonics on the surface.

糖心传媒淏ecause we constrained the inner core糖心传媒檚 age more accurately, we could explore the fact that the present-day inner core is actually composed of two parts,糖心传媒� Tarduno says. 糖心传媒淧late tectonic movements on Earth糖心传媒檚 surface indirectly affected the inner core, and the history of these movements is imprinted deep within Earth in the inner core糖心传媒檚 structure.糖心传媒�

Avoiding a Mars-like fate

Better understanding the dynamics and growth of the inner core and the magnetic field has important implications, not only in uncovering Earth糖心传媒檚 past and predicting its future, but in unraveling the ways in which other planets might form magnetic shields and sustain the conditions necessary to harbor life.

Researchers believe that Mars, for example, once had a magnetic field, but the field dissipated, leaving the planet vulnerable to solar wind and the surface ocean-less. While it is unclear whether the absence of a magnetic field would have caused Earth to meet the same fate, 糖心传媒淓arth certainly would糖心传媒檝e lost much more water if Earth糖心传媒檚 magnetic field had not been regenerated,糖心传媒� Tarduno says. 糖心传媒淭he planet would be much drier and very different than the planet today.糖心传媒�

In terms of planetary evolution, then, the research emphasizes the importance of a magnetic shield and a mechanism to sustain it, he says.

糖心传媒淭his research really highlights the need to have something like a growing inner core that sustains a magnetic field over the entire lifetime糖心传媒攎any billions of years糖心传媒攐f a planet.糖心传媒�

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