Processes occurring deep within the Earth could be responsible for our planet’s changing gravitational field, according to new research that scoured orbital data for clues to the mystery.
The shift occurred nearly two decades ago, between 2006 and 2008, but went unnoticed at the time. Only through a recent reexamination of the data were scientists able to detect gravitational variations likely linked to processes near the Earth’s core.
Action at the Earth’s Core
For decades, scientists have studied Earth’s core, though direct observation remains impossible. The idea that rocks at the core–mantle boundary could be responsible is still a hypothesis, but one consistent with what researchers have inferred from indirect observations of this hidden region.
“It’s a really new observation,” said co-author Isabelle Panet, a geophysicist at the University Gustave Eiffel in Paris, about using observational data as the team has in their new work published in Geophysical Research Letters.
Earth’s layers each have distinct properties: the crust is brittle, the mantle is solid, and the outer core is molten. Where these boundaries meet, some of the planet’s most powerful forces—earthquakes, the magnetic field, and others—are generated.
Collecting Gravitational Field Data
The findings draw on information from GRACE, the U.S.–German Gravity Recovery and Climate Experiment, which consisted of two satellites that orbited Earth in formation from 2002 to 2017. GRACE measured variations in gravity by detecting tiny changes in the satellites’ positions as they responded to mass concentrations on Earth, such as mountain ranges.
Originally, GRACE was designed to monitor large-scale water displacement, including groundwater depletion and glacial melt. Panet, however, had already been applying the data to study mass changes preceding large earthquakes. In this case, the analysis probed even deeper, down to 2,900 kilometers at the core–mantle boundary.
A Strange Signal
The team’s analysis zeroed in on an unusual signal located off the coast of Africa. Peaking in 2007, the detection defied the researchers’ first attempt at an explanation when it couldn’t be correlated to any shifting surface water.
“So at least partially, there has to be an origin within the solid Earth,” Panet says. “It has to come from very deep.”
Other satellite data monitoring Earth’s magnetic field showed disturbances in the same region and time period, suggesting a possible link. The researchers propose that perovskite—a mineral common in mantle rocks—underwent a phase transition under extreme pressure. This change could have increased rock density, triggering shifts in surrounding material and ripples that reached as far down as the core–mantle boundary. These ripples may have deformed the core by up to 10 centimeters, altering molten flow and affecting the planet’s magnetic field. Though the hypothesis best fits the current data, further research will be required to confirm it.
“For the first time, we have convincing evidence of dynamic processes at the base of the mantle that are occurring quickly enough to study as they happen,” said Barbara Romanowicz, a seismologist at the University of California, Berkeley.
While the new findings are unique, Panet and her colleagues now plan to examine data from satellites still in orbit to see if similar events can be found.
The paper, “GRACE Detection of Transient Mass Redistributions During a Mineral Phase Transition in the Deep Mantle,” appeared in Geophysical Research Letters on August 28, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
Source link
