Paul Antonio: Journey to the Center of the Earth

Customizing a machine to make rocks formed about a billion years ago “speak”—it is with this idea that Paul Antonio has definitively established his career. The young paleomagnetism researcher at the Montpellier Geosciences Laboratory will not be returning to his role as a professor of life and Earth sciences, as he secured an ERC Starting Grant last September for his proposal of a new experimental method to refine the dating of the Earth’s inner core.

His UBEICH project is particularly relevant today, as the scientific consensus regarding the formation of the inner core—estimated to have occurred around 600 million years ago—is being challenged. This moment is crucial because it marks the crystallization of the central portion of the core, which was previously liquid and provided the energy needed to restart Earth’s magnetic field. This magnetic field makes our planet habitable by protecting it, in particular, from cosmic radiation. The formation of a solid core allowed Earth to escape the fate of other planets, such as Mars, which lost their magnetic fields early in their geological history.

Billions of magnetic inclusions

 “During my two years as a postdoctoral researcher at the University of Montpellier, I had time to explore the lab’s equipment. And I thought I could adapt it for my research,” says Paul Antonio. The challenge is to measure the intensity of the magnetic field contained within rocks dating back about a billion years, in order to reconstruct the history of Earth’s magnetism during that era. Conventional methods fail to extract ancient magnetic signals from old rocks due to their alteration throughout their geological history.

Paul Antonio proposes measuring these signals directly at the mineral level rather than at the rock level.“The advantage is twofold: silicate minerals contain billions of magnetic inclusions that have been preserved from weathering, and the small size of these inclusions has potentially allowed for the recording of a stable magnetic signal over time,”explains the researcher. In practical terms, rather than working with rock cores a few centimeters thick, he will first grind them to extract the crystals.“Then we’ll need to adapt the UM’s equipment to work with samples on the order of a millimeter,” he notes.

The supercontinent Rodinia

The idea of applying for an ERC grant was suggested to him.“I had submitted several proposals during my time as an assistant professor, including one for a Marie Curie research fellowship, which was rejected despite receiving a very positive evaluation. As a result, the DIPA office at UM encouraged me to apply for an ERC Starting Grant.” It turned out to be a wise decision. Especially since the researcher already has plenty of material to work with. As part of a postdoc studying the supercontinent Rodinia, which existed a billion years ago, he collected numerous rock cores that correspond precisely to the period of crystallization of the inner core.

Today, he looks back with a sense of wonder on a path he hadn’t anticipated in his research. During his first year of a master’s program preparing for the CAPES SVT exam,“a professor who was impressed by my passion for geology encouraged me to pursue a research-oriented master’s degree instead.” There, a visiting professor from Brazil invited him to come and work on a thesis in paleomagnetism. The topic: refining the position of the South American continent 1.8 billion years ago, when all the continents were grouped together into a single supercontinent, Columbia.“The fieldwork—collecting rock samples in the Amazon—convinced me to accept this project,” he recalls.

From São Paulo to Saverdun

So in 2012, Paul Antonio flew to Brazil to explore paleomagnetism. Upon his return in 2016, with no postdoc in sight, he finished writing his dissertation while completing his certification as a middle school teacher at a school in Ariège. Without a moment’s pause, he found himself moving from São Paulo to Saverdun.“I love teaching, but I missed the life of a researcher. I finally decided to set up my own postdoc project.”Acting strategically, he applied for funding from a public funding agency in the state of São Paulo. And he got it. “It wasn’t easy to go back to Brazil, but it was the only way to work on my own research project because there were no opportunities in France.”

His research focus has shifted back a few billion years. By analyzing the magnetic field orientations of rocks formed during that era, he is determining the positions of Africa and South America within the supercontinent Rodinia. Today, Paul Antonio speaks to us via videoconference from Oslo, where he is starting another postdoc at the new Norwegian center of excellence on habitability (PHAB)—a postdoc he applied for“because the probability of winning an ERC grant on the first try is virtually zero, and it was a unique opportunity to develop my research in one of the world’s leading laboratories .” But here he is, the proud recipient of an ERC grant. After his international stint, he will return in January 2024 to build a team of four people and fully embark on his career as a researcher in Montpellier.