A new study from the University of Texas Institute for Geophysics (UTIG) presents evidence that could explain the peculiar one-sided magnetic imprint on Mars, with a magnetic field that covered primarily the southern hemisphere of the planet.
This discovery challenges the previously held assumption that Mars possessed a uniform magnetic field like Earth, which covers the entire globe.
The study’s lead author, Chi Yan, a UTIG research associate at the UT Jackson School of Geosciences, explained that a lopsided magnetic field would correlate with the magnetic imprint observed today.
Researchers speculate that this one-sided magnetic field could arise from the structure of Mars’ inner core, suggesting it may be liquid rather than solid.
Yan noted, “The logic here is that with no solid inner core, it’s much easier to produce hemispheric (one-sided) magnetic fields.
That could have implications for Mars’ ancient dynamo and possibly how long it was able to sustain an atmosphere.”
The findings were published in the journal Geophysical Research Letters and stem from computer simulations designed to model early Mars’ magnetic behavior.
Historically, most studies of early Mars have relied on magnetic field models that depict the planet as having a solid inner core encased in molten iron, similar to Earth.
However, these assumptions shifted after NASA’s InSight lander discovered that Mars’ core is composed of lighter elements than previously believed, leading to speculations about its molten state.
According to co-author Sabine Stanley, a Bloomberg Distinguished Professor at Johns Hopkins University, if Mars’ core is indeed molten now, it is almost certain that it would have been molten approximately 4 billion years ago, when Mars’ magnetic field was active.
To investigate this theory, the researchers conducted numerous simulations of early Mars with a liquid core, running them multiple times on state-of-the-art supercomputers.
In their experiments, the scientists incrementally heated the northern half of Mars’ mantle, making it hotter than the southern half.
This temperature divergence between the northern and southern mantles led to the heat from the core being released predominantly in the southern hemisphere.
In these simulations, the concentrated heat escape was vigorous enough to initiate a dynamo effect, generating a robust magnetic field primarily in the southern hemisphere.
A planetary dynamo is a self-sustaining mechanism that creates a magnetic field through movements in the molten metallic core.
Stanley expressed her excitement, stating, “We had no idea if it was going to explain the magnetic field, so it’s exciting to see that we can create a (single) hemispheric magnetic field with an interior structure that matches what InSight told us Mars’ interior is like today.”
UTIG planetary researcher Doug Hemingway acknowledged the significance of the finding, which offers an intriguing alternative to the common belief that asteroid impacts may have erased evidence of a planet-wide magnetic field in the northern hemisphere’s rocks.
He emphasized that Mars presents an intriguing opportunity for research because of its similarities with Earth and its potential for future exploration.
With the notable differences in topography, terrain, and the magnetic field between Mars’ northern and southern hemispheres, any insights into this asymmetry are highly valuable.
The research was funded by the NASA InSight program, and the simulations were carried out at the Maryland Advanced Research Computing Center.
image source from：https://www.jsg.utexas.edu/news/2025/04/molten-martian-core-could-explain-red-planets-magnetic-quirks/
