The mystery of Mars' magnetic field has puzzled scientists for decades. A new study proposes a surprising explanation for its current asymmetry.
Researchers at the University of Texas simulated a one-sided magnetic field on Mars, based on recent data. This approach could shed light on the magnetic anomalies observed today in the southern hemisphere of the Red Planet. Their model suggests a fully liquid core and uneven internal heating as possible causes.
Simulation of a one-sided magnetic field on early Mars.
Credit: Ankit Barik/Johns Hopkins University
The presence of a fully liquid core on Mars was confirmed by NASA's InSight mission. This discovery challenges previous models that assumed an internal structure similar to Earth's. Computer simulations show that this configuration can generate a magnetic field concentrated in a single hemisphere.
Temperature differences between Mars' northern and southern mantle played a key role in this asymmetry. Heat escaping primarily through the southern hemisphere would have fueled a local dynamo. This mechanism explains the current distribution of magnetic anomalies in the Martian crust.
This theory offers an alternative to hypotheses involving asteroid impacts to explain the disappearance of the magnetic field in the northern hemisphere. It highlights the importance of internal structure and thermal processes in planetary evolution. Mars thus presents a unique case of magnetic evolution.
The results of this study were published in
Geophysical Research Letters. They open new perspectives on the geological and atmospheric history of Mars. Understanding these mechanisms is crucial for tracing the conditions that may have allowed life on the Red Planet.
The simulations were conducted with support from NASA's InSight program. They rely on intensive calculations performed at the Maryland Advanced Research Computing Center. This international collaboration sheds light on the complexity of planetary dynamics.
How does a liquid core influence a planet's magnetic field?
A fully liquid core, like that of Mars, allows for freer convective movements than in a partially solid core. These movements are essential for generating a magnetic field via the dynamo effect.
The composition of the Martian core, rich in light elements, lowers its melting point. This characteristic keeps the core in a liquid state, promoting asymmetric convection currents.
Unlike Earth, where the presence of a solid inner core stabilizes the magnetic field, Mars exhibits more variable dynamics. This difference partly explains the early disappearance of its global magnetic field.
Why are magnetic anomalies concentrated in Mars' southern hemisphere?
The simulations suggest that heat from the Martian core escaped primarily through the southern hemisphere. This asymmetric thermal flow fueled a local dynamo, generating a one-sided magnetic field.
The current magnetic anomalies are thus remnants of this ancient field. They testify to a period when Mars had partial magnetic protection against solar winds.