About 4.6 billion years ago the Solar System was essentially a giant cloud of gas and dust. Over the next few million years this solar nebula flattened into a disk, eventually condensing into the central Sun and surrounding planets. While gravity has long been considered the dominant shaping force, MIT researchers have uncovered ancient magnetic records in the oldest known meteorite material, suggesting that magnetic fields also played a significant role.
The team examined microscopic grains called calcium‑aluminum‑rich inclusions (CAIs) extracted from the Antarctic meteorite DOM 08006, discovered in 2008. These CAIs formed within the first 200 000 years of the Solar System, making them the earliest solid material we can study. By isolating CAIs that contain magnetic minerals such as iron and measuring their remanent magnetization, the scientists detected a magnetic field of roughly 150–600 µT preserved in the grains. This field strength is about three to twelve times stronger than today’s Earth magnetic field and would have been sufficient to drive charged plasma inward within the protoplanetary disk, aiding the Sun’s formation.
Magnetic fields arise from moving electric charges. In the collapsing early nebula, a plasma of charged particles could have spun within the developing disk, generating and sustaining a magnetic field. As the material cooled, magnetic minerals locked in the field’s intensity, preserving it for billions of years. When such minerals arrive on Earth via meteorites, their remanent magnetization provides direct evidence that a magnetic field existed and could have influenced the Solar System’s architecture.
DOM 08006 is regarded as one of the most primitive meteorites, retaining its original mineral composition with minimal alteration, which makes it an ideal sample for probing the earliest magnetic environment. The findings indicate that the magnetic field likely assisted the inward transport of gas in the disk and the aggregation of the Sun and early planetary embryos, and therefore must be incorporated alongside gravity in models of Solar System formation.
The study, a collaboration among MIT, Tsinghua University, Cambridge University, Caltech, and UCLA, appears this week in the Proceedings of the National Academy of Sciences.
Blogger's Review: By extracting a magnetic fingerprint from minute mineral grains, this work provides compelling direct evidence that magnetism was a key player in the Solar System’s infancy, reminding us that any comprehensive planet‑formation theory must account for magnetic dynamics.