New evidence suggests vast hidden magma systems inside Mars
Researchers from the University of Oxford have uncovered evidence that Mars once hosted enormous, Earth-like magmatic systems deep beneath its surface – despite the planet lacking the plate tectonics long thought necessary for this kind of geological complexity. The findings, published today in Nature Astronomy, reveal fascinating new possibilities for how rocky planets become habitable.
A new study led by the University of Oxford suggests that Mars once hosted enormous, interconnected magmatic systems rather than simple isolated volcanoes. Image credit: 24K-Production, Getty Images (with elements provided by NASA).
Mars is often described as a ‘stagnant lid’ planet: unlike Earth, its surface is not broken into moving tectonic plates. Because plate tectonics drives volcanism, recycling and continent–building on Earth, many scientists assumed Mars lacked the conditions needed to produce similarly complex crust. However, this new study challenges that view, suggesting that Mars could have produced highly evolved crust through intense internal recycling.
The study was based on data recorded by NASA’s InSight mission to investigate seismic waves from meteoroid impacts and marsquakes - the Martian equivalent of earthquakes. Researchers from Oxford’s Departments of Earth Sciences and Statistics used the recordings to investigate a mysterious boundary about 24 kilometres beneath the Martian surface. Previous studies had recognised the boundary, but no one knew what it represented. To test the idea that the boundary marked a transition between two different rock types, the Oxford team compared hundreds of possible rock compositions with the seismic data using thermodynamic modelling and statistical techniques.
They found that only ‘ultramafic’ (rich in iron and magnesium, but low in silica) rocks consistently matched the physical properties beneath the 24-km boundary. Whereas the properties above this boundary were better matched to ‘mafic’ (containing a higher proportion of silica) rocks.
The researchers believe that this buried layer likely formed where molten rock pooled deep underground and gradually separated into different materials. This would leave behind a thick residue of dense crystals at the base of the crust while lighter, more evolved melts rose upwards. On Earth, similar processes occur beneath volcanic arcs and are linked to the formation of continents.
“We've traditionally assumed that volcanism on Mars was relatively simple compared to that on Earth. But this discovery suggests the planet could sustain massive, long-lived magmatic systems capable of evolving and reprocessing molten rock throughout the crust. Because these systems are known to generate large metal deposits, Mars may hold significantly more near-surface mineral wealth than previously recognised - boosting its potential for future mining, crewed missions and eventually, permanent settlements.”
The study suggests this layer may extend sideways for hundreds or even thousands of kilometres around Mars’ northern hemisphere, indicating that the Red Planet once hosted enormous, interconnected magmatic systems rather than simple isolated volcanoes. This phenomenon – known as ‘transcrustal magmatism’ was previously thought to be unique to Earth.
These geological processes are closely linked to how planets develop atmospheres, oceans and potentially habitable environments. For instance, on Earth, geological recycling helps regulate climate and supports long-term cycling of water and other volatile elements. Scientists have often assumed plate tectonics were essential for creating these conditions. But the new findings suggest planets may not need Earth-style tectonics to build complex crusts and sustain the conditions that support life.
“One of the big questions in planetary science is whether Earth is unique. If Mars could develop this kind of complex crust without plate tectonics, then maybe the conditions needed for habitability can emerge on more planets than we realised, including those previously dismissed based on size or their apparent lack of tectonic activity.”
The work builds on seismic observations from NASA’s InSight mission, which placed the first seismometer on Mars in 2018 and revealed the planet’s interior in unprecedented detail.
The study was led by researchers from Oxford University’s Department of Earth Sciences in collaboration with the University of Bristol and the University of Oxford’s Department of Statistics.
The paper ‘Seismic evidence for a melt-depleted lower crust and transcrustal magmatism on Mars’ has been published in Nature Astronomy.
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