How did Earth escape the fate of Mars?

A radical event saved Earth’s magnetic field about 550 million years ago – and may also have ensured that life on Earth was possible.

Rochester – Earth’s magnetic field cannot be seen or felt – yet it is there and has a vital function. It protects our planet and life on it from cosmic rays and charged particles from the sun, the so-called solar wind. But this was not always so. About 565 million years ago, the magnetic field strength decreased to ten percent of its current strength – only to return to its previous strength about 550 million years ago.

What happened? To find the answer to this question, researchers from the University of Rochester dug deep underground. Because about 2,900 kilometers beneath our feet something is happening that allows the Earth’s magnetic field to develop in the first place. There, liquid iron swirls in Earth’s outer core and generates electric currents that drive what’s called a geodynamo, which ultimately builds up Earth’s magnetic field.

The renewal of the Earth’s magnetic field with the formation of the Earth’s inner core

“The inner core is very important,” said John Tarduno, a geophysicist at the University of Rochester. communication. Together with a team of researchers, Tarduno discovered what happened 550 million years ago to maintain the Earth’s magnetic field: the solid inner core of the Earth was formed – with disastrous consequences for the Earth, Tarduno stresses: “Shortly before the interior when the core began to grow, the field was The magnetic is on the verge of collapse, but as soon as the inner core started to grow, the field was renewed.”

For many years, researchers have been trying to figure out how the Earth’s magnetic field and core have changed over time. However, as they cannot dig deep enough into the earth for on-site surveys, they have to make do with rocks that were once deep in the earth but have come to the surface over time. Minerals contain tiny magnetic particles that record the direction and strength of the magnetic field as the minerals cool from their molten state.

Rocks from the Earth’s interior allow conclusions to be drawn about the magnetic field

Using a carbon dioxide laser and a superconducting quantum interference device, Tarduno and his team analyzed feldspar crystals from the anorthosite rocks. These crystals have tiny magnetic needles inside that Tarduno says are “perfect magnetic recording devices.” Through the analysis, the researchers were able to find out when the Earth’s inner core formed and the magnetic field renewed.

“Because we were able to narrow down the age of the inner core, we were able to explore the fact that the current inner core is actually made up of two parts,” Tarduno explains. “The movements of tectonic plates at the Earth’s surface have indirectly affected the inner core, and the history of these movements is imprinted deep within the Earth’s interior in the structure of the inner core.”

The study of the Earth’s magnetic field is also interesting for Mars

Tarduno and his team’s study was completed in July 2022 in the journal Nature Communications published, but it is not only important for understanding the evolution of the Earth. It is also important for researchers exploring other planets to know how Earth’s magnetic field came about – it is a significant reason why there is life on Earth at all.

Research posits that there used to be a magnetic field on Mars, for example, but it weakened and eventually disappeared. As a result, the planet was defenseless against the solar wind – the atmosphere eroded away, and the oceans disappeared. Researchers now know why Mars, unlike Earth, did not develop a permanent magnetic field.