Paul Antonio: Journey to the Center of the Earth

Customizing a machine to make rocks that formed around a billion years ago "speak" is the idea that has definitively confirmed Paul Antonio's career path. The young paleomagnetism researcher at the Montpellier Geosciences Laboratory will not return to teaching life and Earth sciences, as last September he was awarded an ERC Starting Grant for his proposal for a new experimental method to refine the dating of the Earth's inner core.

His UBEICH project is particularly relevant given that the scientific consensus surrounding the dating of the creation of the inner core at around 600 million years ago is now being called into question. This moment is crucial because it corresponds to the crystallization of the central part of the core, which was then liquid, providing the energy needed to restart the Earth's magnetic field. The magnetic field makes our planet habitable by protecting it 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 teaching assistant at the University of Montpellier, I had time to explore the laboratory's range of instruments. And I thought to myself that I could adapt them for my research," says Paul Antonio. The challenge is to measure the intensity of the magnetic field contained in rocks dating back around a billion years, in order to reconstruct the history of Earth's magnetism during that period. Conventional approaches are unable 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 scale rather than at the rock scale. "There are two advantages to this: silicate minerals contain billions of magnetic inclusions that have been preserved from weathering, and the small size of these inclusions has potentially allowed them to record a stable magnetic signal over time,"explains the researcher. In practical terms, rather than working on rock cores measuring a few centimeters, he will first grind them to extract the crystals. "Then we will need to adapt the UM's equipment to work with samples measuring around a millimeter," he explains.

Supercontinent Rodinia

The idea of applying for an ERC grant was suggested to him. "I had submitted several projects during my years as an assistant professor, including one for a Marie Curie research grant, which was rejected despite receiving a very good evaluation. As a result, the UM's DIPA department encouraged me to apply for an ERC Starting Grant." It was a good decision. Especially since the researcher already has the material he needs to work with. As part of a post-doc study on 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 surprise on a career path he had not anticipated during his studies. While studying for his Master's degree in preparation for the CAPES SVT (Certificate of Aptitude for Secondary Education in Science andTechnology), "a professor who was impressed by my passion for geology encouraged me to continue with a research Master's degree." There, a visiting Brazilian professor invited him to come and do a thesis on paleomagnetism. The subject: refining the position of the South American continent 1.8 billion years ago, when all the continents were grouped together in a single supercontinent, Columbia. "The fieldwork—going to collect rock samples in the Amazon—convinced me to accept this project," he recalls.

From São Paulo to Saverdun

In 2012, Paul Antonio flew to Brazil to discover paleomagnetism. Upon his return in 2016, with no post-doc in sight, he finished writing his thesis while completing his certification as a middle school teacher at a school in Ariège. Without transition, he went from Sao Paulo to Saverdun. "I love teaching, but I missed the life of a researcher. I finally decided to set up my own post-doc project." 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 studying the magnetic field direction of rocks formed during that period, he is seeking to determine the position of Africa and South America within the supercontinent Rodinia. Today, Paul Antonio speaks to us via videoconference from Oslo, where he is starting another post-doc at the new Norwegian Center of Excellence on Habitability (PHAB) – a post-doc he applied for "because the probability of winning an ERC grant on the first try is almost zero, and it was a unique opportunity to develop my research in one of the most important laboratories in the world ." But now he is the proud recipient of an ERC grant. After his international career, he will return in January 2024 to surround himself with a team of four people and fully embark on his research career in Montpellier.