Deep beneath the Pacific Ocean, the liquid iron at the center of Earth suddenly started flowing eastward in 2010 after moving west for as long as scientists had measured. The reversal was unexpected, unexplained, and caught the attention of researchers using ESA satellites to track the planet's magnetic field.
A 2,200 Kilometer Deep Mystery Beneath the Equatorial Pacific
The molten outer core of Earth sits roughly 2,200 kilometers below the surface. Its movement generates the geomagnetic field that protects the planet from solar radiation. For decades, scientists inferred from magnetic measurements that this liquid iron flowed mostly westward. Then in 2010, a broad region of iron rich fluid beneath the equatorial Pacific switched direction. It began moving strongly eastward instead. The change was dramatic and contradicted the long held assumption that the outer core system moves in a comparatively stable way.
Satellites Tracked the Shift from Space
A study published in the Journal of Studies of Earth's Deep Interior analyzed ground observations and satellite data from 1997 to 2025. Researchers used data from ESA's Swarm and CryoSat missions, along with Germany's CHAMP mission and the Ørsted mission. The satellites measured tiny changes in the magnetic field, allowing scientists to map the flow of molten material below. The data showed that the eastward flow has weakened since 2020, but the reasons for the original reversal remain a mystery.
What This Means for Understanding Earth's Deep Interior
Lead author Frederik Dahl Madsen of the University of Edinburgh School of Geosciences said the reversal raises new questions about the behavior of Earth's deep interior. Scientists now want to know whether the reversal is a short lived fluctuation, part of a repeating oscillation, or a new stable equilibrium for core circulation. The study also hints at possible links between outer core dynamics and changes occurring deeper within the planet. The rise of the strong eastward flow in the Pacific coincided with a change in behavior in the inner core, as inferred from geodesy and seismology. Continued monitoring will be essential to determine how the flow evolves over the coming years.
