Scientists may have finally solved the 50-year-old mystery surrounding the “Mars dichotomy”: the stark contrast between the southern highlands and northern lowlands of Mars.
Using data from NASA’s InSight lander, the researchers hypothesized that the difference lies in internal planetary processes rather than external cosmic collisions.
By analyzing Martian tremors, the team found evidence that the mysterious fissure may have been formed by heat transfer patterns deep within the red planet.
The results were published in a peer-reviewed journal. Research letters in geophysics.
Getty/NASA/JPL/Michael Benson
What is the Mars dichotomy?
The Martian dichotomy was first discovered in the 1970s, when the Viking probe sent incredibly detailed images of our planetary neighbor back to Earth.
The images showed that the southern mountains of Mars rise almost four miles higher than the flat, flat plains of the north.
Additionally, the southern mountains are ancient, cratered and magnetized, dating back to a time when Mars had a global magnetic field. In contrast, the northern lowlands are younger, have fewer craters, and are less magnetized. The crust beneath the Southern Highlands is also significantly thicker.
According to the study’s authors, two main hypotheses have been proposed to explain the skewed appearance of Mars.
The endogenous hypothesis suggests that internal forces such as heat transfer and mantle dynamics within the planet shaped its surface. On the other hand, the exogenous hypothesis attributes these differences to large collisions with the Moon or smaller celestial bodies in Mars’ distant past.
NASA/USGS
What did the scientists find?
Using InSight’s seismometer, researchers analyzed the vibrations of Martian earthquakes to unlock the secrets of the planet’s subsurface. The data showed that seismic waves passing over the southern highlands lose energy faster than those traveling over the northern lowlands, indicating that the rock beneath the southern highlands is significantly hotter.
This temperature difference is consistent with models that suggest that the dichotomy is caused by internal forces.
Scientists believe that early in Mars’ history, the movement of tectonic plates and the dynamics of molten rock may have created an uneven crust. As the planet cooled, movement ceased, creating a “stagnant layer” that preserved the dichotomy.
Convection patterns in Mars’ molten interior fueled the dramatic splitting we see today.
What the authors said
The study authors wrote: “Through InSight’s analysis of earthquakes, we have made significant progress in understanding this phenomenon.
“These findings, supported by geochemical analyzes of Martian meteorites, provide valuable in situ seismological observations that support the ‘endogenous’ hypothesis and suggest that mantle convection plays a crucial role in shaping the Martian crustal dichotomy.”
What happens next?
While this study sheds light on the origins of the dichotomy, it does not completely solve the mystery.
According to the researchers, more data on Martian earthquakes, as well as comparative studies of Earth, Mars and other planetary bodies, will be crucial to confirm the findings.
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Information
Sun, V. and Tkalčić, H. (2025). Constraints on the origin of Southern Highlands earthquakes from the Martian dichotomy. Research letters in geophysics, 52(1), e2024GL110921.
