Researchers at the University of Oxford have found evidence that Mars may once have contained a vast, Earth-like magma system deep beneath its surface. The discovery is significant because Mars does not have the plate tectonics traditionally associated with complex geological activity. Published in Nature Astronomy, the findings offer new insights into how rocky planets evolve—and how geological processes may help create habitable environments.
Mars is generally classified as a “stagnant-lid” planet because, unlike Earth, its outer shell is not divided into moving tectonic plates. On Earth, plate tectonics drives volcanic activity, recycles crustal materials, and contributes to the formation of continents. Since Mars lacks this process, scientists have typically believed that its crust formed through simpler geological mechanisms.
A new study challenges that assumption. The research suggests that Mars may have developed a highly evolved crust through active internal recycling, without requiring Earth-like plate tectonics.
An unexplained boundary 24 kilometers below the surface
The researchers analyzed seismic data collected by NASA’s InSight mission, including waves generated by meteorite impacts and marsquakes.
Scientists from the University of Oxford’s School of Earth Sciences and Department of Statistics examined an unexplained boundary located approximately 24 kilometers beneath the Martian surface. Earlier studies had identified the boundary, but its geological significance remained uncertain.
To determine whether the boundary marked a transition between different rock types, the team compared seismic observations with hundreds of possible mineral and rock compositions. Using thermodynamic modeling and statistical analysis, the researchers identified the materials that best matched the properties detected at different depths.
The analysis showed that rocks below the 24-kilometer boundary are most consistent with “ultramafic” material, which is rich in iron and magnesium but low in silica. Above the boundary, the seismic properties more closely match “mafic” rocks, which contain higher levels of silica.
Evidence of a vast magmatic system beneath Mars
Researchers believe these buried layers may have formed as molten rock accumulated deep underground and gradually separated into different materials. During this process, dense crystals settled toward the base of the crust, while lighter and more chemically evolved melt moved upward.
Similar geological processes occur beneath volcanic arcs on Earth and are linked to the development of continental crust.
Lead author Dr. Tobermory McKay-Champion, formerly of the University of Oxford’s School of Earth Sciences and now at the University of Bristol, said: “We have traditionally thought that volcanism on Mars was relatively simple compared with that on Earth. This discovery suggests that Mars is capable of sustaining a large, long-lived system in which lava evolves and is reprocessed throughout the crust. It raises intriguing questions about how common such systems may be on rocky planets beyond our solar system.”
The buried magmatic layer may also be enormous. According to the research, it could extend across hundreds or even thousands of kilometers beneath Mars’ northern hemisphere.
This suggests that ancient Mars was not shaped solely by isolated volcanoes. Instead, the planet may once have hosted a vast, interconnected magma system spanning a substantial portion of its crust.
This type of geological activity, known as “transcrustal magmatism,” was previously thought to be particularly characteristic of Earth.
What does the discovery mean for habitable planets?
The findings could have important implications for understanding how rocky planets become habitable.
Geological recycling can influence the development of atmospheres, oceans, and environments capable of supporting life. On Earth, these processes help regulate the climate and drive the long-term circulation of water and other volatile elements.
Because plate tectonics contributes significantly to Earth’s geological recycling, scientists have often considered it an important requirement for creating and maintaining habitable conditions. The new evidence from Mars suggests that complex crustal evolution and large-scale geological recycling may also occur on planets without Earth-like tectonics.
Co-author Professor John Wade, from the University of Oxford’s Department of Earth Sciences, said: “One of the big questions in planetary science is whether Earth is unique. If Mars was able to develop this kind of complex crust without plate tectonics, then the conditions necessary for habitability could emerge on more planets than we realize—including worlds that have previously been overlooked because of their size or apparent lack of tectonic deformation.”
NASA’s InSight mission reveals Mars’ hidden interior
The study is based on seismic observations from NASA’s InSight mission, which placed the first seismometer on Mars in 2018. The mission provided scientists with an unprecedented opportunity to study the planet’s internal structure and composition.
The research was led by scientists from the University of Oxford’s School of Earth Sciences, in collaboration with researchers at the University of Bristol and the University of Oxford’s Department of Statistics.
Source: www.sciencedaily.com