Scientists at the Massachusetts Institute of Technology have identified what they describe as ancient magnetic records inside calcium-aluminum-rich inclusions, or CAIs. These tiny mineral-rich objects formed during the first 200,000 years of solar system history, making them among the oldest solid materials available for laboratory study. Their remanent magnetization indicates that a magnetic field existed while the solar nebula—the rotating cloud from which the Sun and planets emerged—was still collapsing and transforming into a protoplanetary disk.

The discovery challenges the idea that gravity alone drove the earliest stages of planetary formation. Although gravity pulled gas and dust inward, the researchers argue that magnetic forces may have helped transport material through the young disk and toward the growing Sun. Their measurements suggest that the ancient nebular magnetic field had a strength of roughly 150 to 600 microteslas. That range is approximately three to twelve times stronger than Earth’s magnetic field at the surface today, indicating that magnetism was not a minor background effect but potentially a major component of the solar system’s birth.

The evidence comes from meteorite DOM 08006, recovered in 2008 from the Dominion Range in Antarctica. The meteorite is considered exceptionally primitive because it experienced remarkably little chemical and geological alteration after forming. Many meteorites have been repeatedly modified during their long histories: they may have become part of water-rich asteroids, been heated or fractured, transported through the asteroid belt, and eventually delivered to Earth. DOM 08006, by contrast, appears to have preserved an unusually clear record of the environment in which its minerals first formed.

Within small samples of the meteorite, the research team isolated CAIs containing iron-bearing minerals capable of recording magnetic fields. When these minerals cooled or crystallized in the presence of an external field, their magnetic moments could become aligned. Later, as the minerals hardened, that alignment was locked into the crystal structure. This process, known as remanent magnetization, can preserve the direction and intensity of an ancient magnetic field for billions of years—provided the material is not subsequently heated, chemically altered, or exposed to stronger fields that overwrite the original signal.

Reading such a record is technically difficult. CAIs are extremely small, chemically complex, and variable even within a single millimeter-sized fragment. The researchers therefore had to identify suitable inclusions, determine which minerals could carry a stable magnetic signal, and test whether the magnetization was genuinely inherited from the solar nebula rather than produced by later events. The team used a series of sensitive paleomagnetic measurements designed to separate primary magnetization from contamination and secondary magnetic overprints. The surviving signal was consistent with a substantial field present during the earliest stage of solar system formation.

The result builds on earlier work by the same research group, which found evidence for a magnetic field approximately two million years after the solar system began forming. By that later time, the Sun was probably already established and the first planetary building blocks were beginning to assemble. The new measurements push the magnetic record back even farther, into an era when the central star itself may still have been forming. This timing is crucial because it points to magnetism operating before planets existed, when the solar nebula was still being converted from a roughly spherical cloud into a flattened, rapidly rotating disk.

Magnetic fields can influence a protoplanetary disk through interactions with ionized gas, or plasma. As charged particles move through the disk, they generate currents and couple the gas to the field. Those interactions can redistribute angular momentum—the rotational motion that otherwise prevents material from falling directly into the center. If magnetic stresses carried angular momentum outward, gas could move inward toward the growing Sun while the disk continued to rotate. Magnetic turbulence and disk winds may also have lifted material away from the disk or transported it across large distances, helping determine where and how solids condensed into asteroids and planets.

“This transition, from a spherical cloud to a protoplanetary disk, is one of the most significant events in all of solar system history,” says Benjamin Weiss, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT. Gravity clearly played a central role, he notes, but the new measurements suggest that magnetism also helped shape the process. Cauê Borlina, the study’s lead author and now an assistant professor at Purdue University, says the finding addresses a long-standing question about the period before planets began forming, when the disk existed but its architecture was still being established.

The researchers emphasize that the discovery does not replace gravity with magnetism. Instead, it adds magnetic fields to the physical ingredients needed to explain the solar system’s earliest evolution. The field recorded in DOM 08006 may have influenced the rate at which gas accreted onto the young Sun, the distribution of solids across the disk, and the conditions under which the first planetary seeds emerged. Because similar magnetic processes operate in disks around young stars elsewhere in the galaxy, the finding could also help scientists understand how common planetary systems are assembled. The study appears in the Proceedings of the National Academy of Sciences and was supported in part by NASA.

Subject of Research: Ancient magnetic fields in the early solar nebula and their role in solar system formation.

Article Title: Paleomagnetic evidence for a nebular magnetic field from calcium-aluminum-rich inclusions

News Publication Date: 24-Aug-2026

Web References: http://dx.doi.org/10.7288/V4/MAGIC/20586

References: Proceedings of the National Academy of Sciences; DOI: 10.7288/V4/MAGIC/20586

Keywords: Solar system formation, solar nebula, magnetic fields, meteorites, calcium-aluminum-rich inclusions, CAIs, paleomagnetism, protoplanetary disks, planetary science, astrophysics, minerals, magnetism

The solar nebula—the cloud of gas and dust from which our solar system formed—was permeated by weak yet consistent magnetic fields generated by ionized gases. Understanding the interplay between this magnetic environment and early-formed solid materials enables scientists to reconstruct the conditions that governed planetary formation and disk evolution. Materials that accreted and underwent alteration within this primordial environment often lock in a magnetic signature as natural remanent magnetization, which can be preserved for billions of years, serving as a time capsule for solar system history.

Asteroid Ryugu, a near-Earth, carbon-rich rubble pile asteroid, originated from the catastrophic disruption of a larger parent body and is thought to harbor some of the most primitive solar system materials. The Hayabusa2 mission, spearheaded by the Japan Aerospace Exploration Agency (JAXA), successfully returned submillimeter-sized Ryugu particles to Earth in 2020, affording researchers direct access to pristine extraterrestrial material with minimal terrestrial magnetic contamination.

Previous studies analyzing the NRM of Ryugu samples have produced varying interpretations due to limited sample sizes and analytical sensitivity. Addressing this challenge, Associate Professor Masahiko Sato and his team conducted a comprehensive series of stepwise alternating field demagnetization (AFD) measurements on 28 individual Ryugu particles. Utilizing one of the world’s most sensitive superconducting quantum interference device (SQUID) magnetometers at the University of Tokyo, their methodological advances enabled precise separation of magnetic components.

Among the 28 studied particles, 23 exhibited stable NRM signatures, with several displaying complex, multi-component magnetization indicative of varied magnetization histories. Notably, one particle revealed spatially inhomogeneous remanent magnetization directions, signaling that some magnetization was acquired before full solidification of the particle itself. This critical observation rules out magnetization attributed to recent processes such as spacecraft handling or terrestrial contamination, confirming that the magnetization preserved is intrinsic and ancient.

The team interprets these magnetization characteristics as chemical remanent magnetization (CRM), consistent with growth of framboidal magnetite mineral structures within the Ryugu particles. The formation of these minute magnetic minerals is attributed to water-driven alteration processes on Ryugu’s parent body, demonstrating the role of aqueous alteration in the early solar system. Magnetite framboids are known for their stable magnetic properties, which make them excellent recorders of paleomagnetic fields.

Dating this magnetization to within approximately 3 to 7 million years of solar system formation situates the recorded magnetic fields in an era critical for the accretion and differentiation of early planetesimals. The preserved magnetic signal offers a window into the magnitude and temporal evolution of magnetic fields in the solar nebula during the epoch of planetary formation, thereby refining theoretical models of disk dynamics and mass transport.

These revelations have profound implications for our understanding of the conditions under which primitive materials—and eventually planets—formed. The data provide vital constraints on the timing and nature of magnetic field generation in the protoplanetary disk, a factor influencing dust coagulation, angular momentum transport, and the consequent structural evolution of the early solar nebula.

Dr. Sato emphasizes that “our high-sensitivity magnetic measurements on microsamples from asteroid Ryugu have resolved previous ambiguities about their natural remanence.” This breakthrough underscores the importance of high-precision paleomagnetic techniques in planetary science and the study of extraterrestrial materials to decipher the solar system’s formative processes.

The success of these meticulous analyses depended on advanced laboratory capabilities and careful curation protocols that prevented contamination. The research leverages interdisciplinary expertise spanning physics, mineralogy, and planetary science, showcasing the scientific value of sample-return missions like Hayabusa2.

Tokyo University of Science’s dedication to cutting-edge research and technological excellence has facilitated this landmark study. The university, with its long history of contributions to Earth and planetary magnetism research, continues to lead investigations that bridge atomic-scale phenomena with vast cosmic timescales.

Looking ahead, these findings open avenues for more detailed paleomagnetic investigations not only of Ryugu particles but also of samples returned from other celestial bodies, such as the Moon and Mars. Such studies will undoubtedly refine our understanding of early solar system evolution and the interplay between magnetic fields and planetary genesis.

This investigation marks a significant stride in unraveling the intricate magnetic history preserved in asteroid particles, advancing both scientific knowledge and the broader narrative of our cosmic origins.

Subject of Research: Not applicable

Article Title: Characteristics of Natural Remanence Records in Fine-Grained Particles Returned From Asteroid Ryugu

News Publication Date: 10-Feb-2026

References: DOI: 10.1029/2025JE009265

Image Credits: Associate Professor Masahiko Sato, Tokyo University of Science, Japan

Keywords

Natural remanent magnetization, Ryugu asteroid, Hayabusa2, framboidal magnetite, chemical remanent magnetization, superconducting quantum interference device, protoplanetary disk, solar nebula magnetic fields, paleomagnetism, early solar system evolution, planetary formation, aqueous alteration