MIT researchers have uncovered signs of a strong magnetic field at work during the very earliest days of the Solar System, using ancient meteorites as evidence. The findings point to magnetism as a significant force in shaping the young solar system. The study focuses on some of the oldest materials in our cosmic neighborhood, revealing a magnetic influence present within the first 200,000 years of its existence.
In the Proceedings of the National Academy of Sciences, a finding has overturned the assumption that gravity was the sole force shaping the solar nebula. The research suggests that magnetism might have partnered with gravity to draw in the early material as the sun came into being.
The Meteorite That Preserved an Ancient Record
Researchers concentrated on calcium-aluminum-rich inclusions, or CAIs, which came into being during the solar system’s opening 200,000 years. These particles make up some of the earliest known material from that era and were extracted from a meteorite found in Antarctica in 2008.
DOM 08006, a meteorite discovered in the mountains of the East Antarctic Ice Sheet known as the Dominion Range, has an unusually primitive composition. That means it has undergone less alteration than any other meteorite.
Cauê Borlina, who is now an assistant professor at Purdue University, was the first author of the study. It was he who said “That’s where the debate still resides, and that’s where we’re operating now,”.
What the Magnetic Signatures Show
Tiny mineral grains were separated from the meteorite by the researchers, who went on to identify several CAIs holding naturally magnetic materials, among which iron was present. They then put those grains to the test, checking whether any ancient magnetism had survived within them.
The findings indicated a strong magnetic field was already in existence during the solar nebula phase. The team estimates it exceeded the strength of Earth’s magnetic field at present.
“This transition, from a spherical cloud to a protoplanetary disk, is one of the most significant events in all of solar system history,” said Benjamin Weiss, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT. “It has long been theorized that gravity caused this, but our measurements show magnetism likely played a role.”
How Magnetism May Have Shaped the Disk
A moving mass of charged matter produces a magnetic field, and during the earliest phase of solar system creation, the falling cloud of gas and dust might have produced a plasma with charged particles within it. That motion, as the particles moved around inside the forming disk, could have built up and kept a magnetic field going.
Weiss and his team figured that if a magnetic field existed, it would leave a trace on some of the material forming inside the disk. The idea was that tiny magnetic minerals might record the strength of the surrounding field.
Before the solar system was fully assembled, researchers found evidence of magnetism from around 2 million years after it started to form. Scientists believe the sun existed by then and the planets were starting to come together. That prior research suggested magnetic fields might have played a part in how the planets took shape.
“Nowadays people don’t debate whether magnetism is present when planets are forming. But the debate is around the very early solar system, before planets are forming, when there’s just a disk,” Borlina said. “That’s where the debate still resides, and that’s where we’re operating now.”
The Team Behind the Research
Weiss’s team from MIT includes Borlina, Elias Mansbach PhD ’24, and Nilanjan Chatterjee. The remaining contributors come from outside institutions:
- Xue-Ning Bai of Tsinghua University
- Po-Yen Tung and Richard Harrison of Cambridge University
- François Tissot of Caltech
- Kevin McKeegan of the University of California at Los Angeles
This work contributes to mounting proof that magnetism played a major role in the early solar system. The study indicates magnetism may have assisted in pulling ancient material toward the center as the infant sun took shape, operating with gravity to form the disk that later gave rise to the sun and the planets.
Why the Meteorite Was a Good Target
The DOM 08006, because of its unusually well-preserved state, is a particularly good place to look for signs of magnetic fields from the very first moments of our solar system. It has endured less change than any other meteorite, which makes it stand out as a promising target for study.
“Other meteorites went through many different processes over this 4.5 billion year history,” Weiss said. “They were formed in the solar nebula, then added to bodies with water, then got destroyed, moved to the asteroid belt, and then landed here. But somehow, DOM has experienced less alteration than any other meteorite.”
The CAIs within the meteorite vary widely and do not match up evenly, even across a single 1-millimeter fragment of the stone. The team had to work hard to figure out which kinds of CAIs they were actually dealing with.
The study pushes the search for magnetic fields back to the solar system’s earliest moments, before planets had even begun to form. The research shows ancient magnetic fields stronger than Earth’s may have shaped the solar nebula before the sun and planets formed, pushing matter inward as the young sun grew.
Source material: “Ancient meteorites reveal a powerful force that helped build the Solar System,” ScienceDaily.
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