4.6-Billion-Year-Old Meteorite Reveals a Surprisingly Strong Primordial Magnetic Field

Researchers led by the Massachusetts Institute of Technology (MIT) have found evidence of a surprisingly strong magnetic field during the solar system's first 200,000 years, before the Sun had fully formed. The evidence comes from microscopic mineral grains preserved inside a meteorite found in Antarctica in 2008. The findings, led by MIT professor Benjamin Weiss and Borlina, a former MIT graduate student now an assistant professor at Purdue University, appear in the Proceedings of the National Academy of Sciences (PNAS).

The researchers examined DOM 08006, a meteorite found in 2008 in the Dominion Range along the East Antarctic Ice Sheet. It is one of the most primitive meteorites known, having changed far less than most others over its roughly 4.6-billion-year history. Inside it, the team identified calcium-aluminum-rich inclusions (CAIs) — tiny mineral grains that formed during the solar system's first 200,000 years and are the oldest known material from that period.

Some of the CAIs contained naturally magnetic minerals, including iron, capable of recording the strength of any magnetic field present when they formed — a property called remanent magnetization. The measurements indicate the early solar system's magnetic field measured roughly 150 to 600 microteslas, about three to 12 times stronger than Earth's magnetic field today.

The finding pushes evidence of solar-system magnetism further back than before. The researchers had previously found signs of magnetic fields from about 2 million years after formation began, when the Sun had already formed and planets were assembling. Weiss said the shift from a spherical cloud to a protoplanetary disk is among the most significant events in solar system history, and that while gravity has long been credited, the new measurements show magnetism likely played a role too.

Borlina said the fields likely helped move gas from the protoplanetary disk inward toward the forming Sun, working alongside gravity — a factor he said should be included in explaining how the Sun and planets formed.