Although the magnetic field of Mars hasn’t been in effect for billions of years, the evidence it left behind may suggest that the planet’s core is entirely liquid. Magnetic imprints still exist on Mars, but they’re centered around its southern half, raising a mystery that has left scientists scratching their heads for years. Recent research, however, has proposed a promising answer: the molten Martian core likely generated a magnetic field that only covered the Red Planet’s southern hemisphere.
A new study published in the journal Geophysical Research Letters offers an overhauled perspective on Mars’ magnetic field, which dissipated around 4 billion years ago. This theory shows how Mars, despite sharing a few similarities with Earth, has a much different history full of unexpected surprises.
How Did Mars Lose Its Magnetic Field?
The history of magnetism on Mars remains a critical field of study since it is closely tied to the planet’s potential capacity for life billions of years ago. Mars’ magnetic field was once generated by its dynamo, a mechanism shaped by currents within the planet’s liquid core (thought to be made of iron, sulfur, and hydrogen).
The magnetic field would have protected Mars from space radiation and solar wind, just like Earth’s magnetic field does for our planet today. But why did Mars lose its magnetic field while Earth still has one? It may have something to do with the Martian core cooling down, causing its dynamo to collapse. Afterwards, the planet’s oceans vanished, as did any forms of life that lived there.
Read More: Wave Ripples Prove the Existence of Ice-Free Lakes on Ancient Mars
Simulating a Liquid Core
The new study indicates that Mars’ magnetic field may not have been entirely similar to Earth’s because of the planet’s presumably liquid core.
“The logic here is that with no solid inner core, it’s much easier to produce hemispheric (one-sided) magnetic fields,” said lead author Chi Yan, a research associate at the University of Texas Jackson School of Geosciences, in a statement. “That could have implications for Mars’ ancient dynamo and possibly how long it was able to sustain an atmosphere.”
Researchers got the idea to simulate a fully liquid core from NASA’s InSight lander, which landed on Mars in 2018 and found that its core consisted of elements that were lighter than expected. This points to the whole Martian core being molten — Earth’s core, on the other hand, is made up of a solid inner core and a liquid outer core.
A One-Sided Magnetic Field
Influenced by the InSight findings, the researchers created simulations of early Mars with a liquid core. They ran the simulations a dozen times on supercomputers, making the planet’s northern half of the mantle hotter than the south with each successive test.
Eventually, this revealed that heat from the core would escape at the southern end of Mars, generating a strong magnetic field that only encompassed the southern hemisphere.
“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,” said co-author Sabine Stanley, a physicist at Johns Hopkins University, in a statement.
This theory of a one-sided magnetic field stands in stark contrast to prior theories stating that asteroid impacts were responsible for destroying evidence of a planet-wide magnetic field on the northern hemisphere.
The breakdown of Mars’ magnetic field ultimately made the planet inhospitable. Although much of the planet’s history is still undetermined, the magnetism displayed early in its existence may yet hold further answers on a bygone era when Martian life may have been possible.
Read More: Newly Discovered Mars Molecules Resemble Structures Critical for Life on Earth
Article Sources
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Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
