Scientists Discover New Way to Image Earth’s Interior Using Magnetic Fields

An international team of researchers has produced images of the Earth's interior using a new method using magnetic fields.

The work, published in the journal Science Advances, involves measuring the magnetic fields from the Earth's ocean to come up with information about the planet's interior structure and composition.

According to the researchers, the work could provide scientists with new ways to image and understand the Earth's interior as well as help them probe the interior of other celestial bodies with tidal saltwater.

"The really exciting thing is that we're using satellite data, meaning nothing that has to actually touch the planet, to probe the interior of the Earth," Neesha Schnepf from the University of Colorado Boulder and also from NOAA's National Centers for Environmental Information and a member of the Cooperative Institute for Research in Environmental Sciences (CIRES), said in a statement.

When salts in seawater dissolve into ions or charged particles that conduct electricity, they interact with the Earth's magnetic field. The movement of salt water due to tides produces an electric current that generates smaller magnetic fields. According to previous studies, the satellites that monitor the Earth's magnetic field could also detect the ocean's magnetic field, but it is not yet certain how the data could be used to study the Earth's subsurface structure.

"There are not that many ways to 'look' inside our planet," Alexander Grayver, a geophysicist at the Swiss Federal Institute of Technology in Zurich, Switzerland and lead author of the study, said in a report by Space.com. "Electrical conductivity is one of the very few properties we can sense at depths. Since electrical conductivity of a rock depends on its temperature, water content, pressure and mineral composition, we use it as a proxy to infer this information."

According to the research team, studying seismic tomography or the movement of seismic waves around the planet captured by ground-based instruments could provide information about the planet's interior structure. To do this, Grayver and his team used data from satellites that measure magnetic fields and also captured the sloshing signals of tides in the ocean.

The researchers combined satellite data with their sophisticated inverse modeling technique to determine which interior changes below the Earth's crust could cause similar magnetic pattern. The findings complemented results from seismic tomography. They found that a layer of the Earth's lithosphere and upper mantle about 72 km (45 miles) does not conduct electric currents very well, and that there is a sharp increase in conductivity at the boundary between the lithosphere and the asthenosphere, which is a deeper layer.

The scientists also said that the satellite technique could also be used in studying other planet's moons such as Jupiter's Europa and Ganymede, which are believed to have tidally moving saltwater.