How tiny iron grains preserved the solar system's first magnetic fingerprints
In short: Scientists long doubted if ancient meteorites could truly hold onto magnetic records from the dawn of time. New research into the Bishunpur meteorite reveals that complex, swirling magnetic structures in microscopic iron grains are actually more stable than simple magnets, offering a window into our solar system's 4.6-billion-year history.
The formation of our solar system 4.6 billion years ago was a remarkably rapid process, involving a cloud of gas and dust that coalesced into the Sun and planets within just a few million years. Researchers have long sought to understand how this accretion occurred so quickly without the early planets being pulled into the Sun. Magnetic fields, alongside gravity, are believed to have played a crucial role in shaping this early architecture.
To find evidence, scientists studied the Bishunorpuri meteorite, which fell in Jharkhand, India, and has been part of the Natural History Museum's collection for decades. This specific meteorite is invaluable because it is unaltered, having escaped the heating or water damage that typically alters mineral compositions. By using rare electron microscopy at the Ernst Ruska-Centre and the Peter Grünberg Institute in Jülich, Germany, researchers examined nanometric grains of low-Ni kamacite (metallic iron) encased in dusty olivine crystals.
The study challenged previous assumptions in rock magnetism. Earlier theories focused on uniform magnetization, similar to a classic bar magnet. However, the team, including Prof. Sara Russell and Jay Shah, discovered that these tiny grains contain complex, multi-vortex magnetic structures. Using off-axis electron holography and numerical modeling, they demonstrated that these non-uniform, swirling magnetic fields are stable over billions of years. This confirms that these grains can reliably carry magnetic recordings from the solar system's earliest stages of accretion.
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Sources
- Summary by Intellect · source: The Quietest, Oldest, and Magnetic-iest Science of 2018
- Also: The oldest magnetic record in our solar system identified using nanometric imaging and numerical modeling - PubMed
- Also: Meteorite reveals the oldest magnets in the solar system | Natural History Museum
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