This prevented the Earth from becoming an uninhabited planet

View of the planet Earth from space. / File, Archive

Science | geology

New research suggests our planet's solid inner core formed 550 million years ago and restored the geomagnetic field

Elena Martin Lopez

Life on our planet, as we know it, could not exist without the Earth's geomagnetic field. Without it, our planet would be exposed to dangerous streams of radiation from the sun, also called solar winds. There was a time when this field was so weak that it was on the verge of disappearing, which could have led to the Earth being an uninhabited planet. Luckily, he recovered. How? The keys to this 'mystery' have been collected in a
study by a team of scientists from the University of Rochester, recently published in the journal Nature Communications.

To understand it better, let's go back a bit to our school years, when we learned that the Earth is made up of layers (crust, mantle, liquid outer core and solid inner core). In the liquid outer core, the molten iron causes electrical currents and drives a phenomenon called a geodynamo, giving rise to the magnetic field. The researchers suggest that, about 565 million years ago, the strength of the geomagnetic field decreased to 10% of its current strength. Fifteen million years later, however, this field began to renew rapidly and recovered in a few tens of millions of years (a short time span on geologic time scales).

The researchers believe that this quick recovery was due to the fact that, just at that moment, the solid inner core of the Earth began to form. “To generate and maintain a magnetic field, convection (heat transfer) must occur in the liquid core of the planet. That convection can be a consequence of the heat that is released from the outer core to the mantle, or of the energy released by the solid inner core. If neither of these two options is available, the magnetic field collapses,” explains John Tarduno, Professor of Geophysics in the Department of Earth and Environmental Sciences and dean of research for Arts, Sciences, and Engineering at Rochester.

The magnetic field protects the Earth from solar winds.

If these streams of radiation

the Sun releases into space reach our planet, many species could disappear.

Cortex

Where is it

life

Outer core

liquid

Where is the magnetic field created?

The molten iron in the outer core generates electrical currents, giving rise to a phenomenon called

geodynamo which produces the magnetic field.

Source: University of Rochester.

magnetic field

protects the Earth from solar winds.

If these streams of radiation that the Sun releases into space

reach our planet, many species could disappear.

Cortex

where is life

Nucleus

solid inside

Composed of iron

and nickel.

Outer core

liquid

Where is the magnetic field created?

The molten iron in the outer core generates

electrical currents giving rise to a phenomenon called geodynamo that produces

the magnetic field.

Source: University of Rochester.

If these currents of radiation that the Sun releases

into space will reach our planet, many

species could disappear.

magnetic field

protects the Earth from solar winds.

Cortex

Where is it

life

Nucleus

solid inside

Composed of iron and nickel.

Outer core

liquid

where it is created

the magnetic field.

The molten iron in the outer core generates

electric currents giving rise to a

phenomenon called

geodynamo that produces

the magnetic field.

Source: University of Rochester.

In the case of the Earth, the creation of the solid inner core was decisive in restoring the magnetic field. “The solid inner core is tremendously important. As soon as the field grew it regenerated. The key part of the new research is to establish the moment when the ultraweak magnetic field regained its strength, which allows us to know when the solid inner core of the Earth began to grow and to estimate its age more precisely (about 550 million years). )”, says Tarduno. This also allowed them to explore the fact that the current solid inner core is actually made up of two parts.

The bad news is that measuring the magnetic field directly is impossible, both because of its location (more than 6,000 km deep) and because of the extreme temperatures of the Earth's core (approximately 6,000 degrees Celsius, about as hot as the Earth's surface). sun). The good news is that the minerals that rise to the surface of the Earth contain tiny magnetic particles that can be analyzed. In this study, Tarduno and his team analyzed feldspar crystals from anorthosite rock to better constrain the age and growth of the inner core.

Present and future of the Earth

Better understanding the dynamics and growth of the inner core and the magnetic field allows us to deepen our knowledge of our planet. “If the magnetic field had not regenerated, the atmosphere would have been unprotected from the solar wind, it would have slowly deteriorated and the terrestrial water would have been removed. Earth probably wouldn't have looked like Mars today, but we guess it would have been much drier without the shielding protection provided by the magnetic field," explains Tarduno. "This research really highlights the need for a habitable planet to have a growing inner core that will sustain the magnetic field for its entire lifetime, that is, many billions of years."

A representation of the Earth, first without an inner core; second, with an inner core that began to grow, about 550 million years ago; third, with an outermost and innermost inner core, about 450 million years ago. /

University of Rochester/Michael Osadciw

The problem is that, as has been verified from the SWARM satellite constellation of the European Space Agency (ESA), the Earth's magnetic field is gradually weakening in an area that stretches from Africa to South America, a phenomenon that has baptized as the “South Atlantic anomaly”. A priori, “this is only a concern for satellite operations (they can short-circuit, fail and permanently damage), but if it continues to weaken it could lead to short-term ozone depletion, which would increase the risks of skin cancer in some regions", warns Tarduno.

The magnetic field of Mars

The findings, however, serve not only to uncover Earth's past and predict its future, but also to unravel the ways in which other planets can form magnetic shields and support the conditions necessary to support life. Researchers believe that Mars, for example, once had a magnetic field that dissipated at some point, leaving the planet vulnerable to solar wind and an oceanless surface.

"Early in Martian history, sometime between 4.1 and 3.7 billion years ago, the Martian magnetic field died, we think because energy sources were limited to maintain the convection process," explains Tarduno. The question is, could the Martian magnetic field regenerate itself, as it did on Earth, making it habitable again? "Unfortunately, on Mars, the two possible energy sources for convection - heat transfer across the Martian core-mantle boundary or chemical convection in a growing inner core - seem to lack the necessary energy, and this cannot be changed. Still, the idea of ​​man-made mini-magnetospheres (mimicking the magnetic field) on Mars to house areas for future habitation is indeed a considerable option for the future."

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