My work was divided into three work packages (WP).
In WP1, I designed and conducted an experiment to determine an empirical relationship between the magnetization acquired by magnetite while growing in a magnetic field, and the intensity of this field. For this, I grew magnetite inside non-magnetic natural samples by heating them in a controlled atmosphere in a known magnetic field. Comparing the intensity of the field applied to the intensity of the magnetization acquired by magnetite, I derived an empirical relationship applicable to other samples carrying magnetite.
In WP2, I conducted paleomagnetic investigations on several samples that possibly carried the record of the solar nebula magnetic field. I started by analyzed the magnetic properties and record of the oldest meteorite known so far named Erg Chech 002. I discovered a very robust magnetic record. After ruling out potential sources of magnetic contamination, and comparing these data to the epoch of magnetization acquisition, I concluded that Erg Chech 002 recorded the solar nebula magnetic field, making it the oldest record available. I then focused on two samples returned from the asteroid Ryugu by the JAXA Hayabusa 2 mission. I conducted a paleomagnetic investigation of both samples and, found out that this material only experienced a weak or null magnetic field at the time the magnetic minerals formed (a few million years after the onset of solar system formation). This led me to conclude that the returned material either formed late, after the solar nebula field dissipated, or at a large distance from the sun, where the magnetic field strength was weaker. Finally, I supervised the work of a MSc student for five months, where she and I analyzed the magnetic properties and record of more than 10 hydrated meteorites. These meteorites all carry a stable, ancient magnetization, which we interpret as the record of the solar nebula field. Using the empirical relationship of WP1, we estimate that these meteorites recorded a field between 2 and 20 µT intensity.
In WP3, I conducted two synchrotron measurement campaigns to characterize the magnetic properties of equiatomic Fe-Ni found in meteorites. In particular, I developed and validated a new sample preparation protocol, allowing me to spatially resolve magnetic features at the 50-nm scale.
In terms of dissemination, the work conducted in WP1 is the object of a publication (Maurel and Gattacceca; 2023) in JGR Planets. Two papers, on Erg Chech 002 and Ryugu samples, are under review for WP2. I was invited to present my work on WP1 and WP2 at the AGU Fall Meeting 2022 and Core2Disk International Workship 2023. I also presented my results at multiple conferences. I also led several outreach activities with children, students, and adults (science fair, speed meeting, European researcher night, intervention in class).
