Of all the planets in the solar system, Earth occupies the highest prominence. The constant shifting of tectonic plates and the presence of life and evolution make it truly unique.In contrast, Mars looks like a planet whose best days are over. Its volcanoes are extinct, its crust remains, and it has not even developed the shifting tectonic plates that constantly reshape the Earth.But now, a new discovery has surprised scientists. Deep within the surface of Mars, researchers found evidence of a massive magma system that extended across the planet’s entire crust.
Shocking discovery
Until now, scientists thought this type of geological plumbing required plate tectonics.
But now, they wonder, if Mars was able to build such a complex interior without moving plates, the ingredients for life might be more common on the planet.The evidence comes from NASA’s InSight lander, which placed the first seismometer on the planet’s surface in 2018. It spent the next few years recording the planet’s faint internal tremors. Some of these tremors came from meteor strikes. Others came from Martian quakes, the Martian version of earthquakes.
These recordings helped researchers read the structure beneath the lander more clearly and deeply than before. A previous analysis of the same data showed that the Martian crust is built in layers rather than as a single solid mass. Water-bearing rocks lie near the top, giving way to denser material below.About 15 miles below the crust, the mystery flowed. The speed of seismic waves changed sharply at this depth, marking a clear boundary, but it’s still unclear what lies within.
While some scientists considered it an ancient layer of the crust, others saw it as a normal layer in the lower crust.
Two-layer story
To understand what the boundary really means, a team led by geologist Dr Tobermory Mackay-Champion from the University of Oxford took a different approach. He and his colleagues have collected hundreds of possible rock recipes for Mars’ interior. For each recipe, they calculated how fast seismic waves should travel, and then compared those predictions to the speeds measured by InSight.
The statistics did the rest.
The scoring system ranks the suitability of each rock type to the data, layer by layer.Above the boundary, the rocks behaved like basalt, the dark volcanic rock that covers much of the planet’s surface. But underneath, the wave speeds were much faster than the basalt. Instead, they matched a denser rock that was low in silica and rich in iron and magnesium, the type geologists call ultramafic.The numbers also appeared unbalanced. The top rock had an 86% chance of resembling basalt while the bottom rock had a 91% chance of being ultramafic.
Together, the results describe a band of dense, iron-rich rock about 9 miles thick at the base of the crust, beginning about 15 miles downward, according to the study published in the journal Nature Astronomy.
Once upon a time there was magma…
A layer like this does not form easily. The team reads it as a thick pile of crystals that accumulated as magma pooled deep in the Earth’s crust and slowly cooled. As the magma crystallized beneath Mars, the heavier minerals settled and accumulated, while the lighter minerals melted to the top.At the temperatures that the Martian crust normally reaches, its lower layers should not have become hot enough to melt. Their thermal models show that only an unusually strong flow of heat from below could trigger this melting. The most likely source was the hot mantle rising underneath and pushing fresh magma into the crust. Together these processes form transcrustal magma, a continuous network of rocks that melt, pool and rise across the entire thickness of the crust.
Possibility of life
On Earth, systems like these exist beneath volcanic chains and help build continents. It was thought that they needed tectonic plates to be able to function at all. What the team saw on Mars is similar to processes that have been studied on Earth for decades. A study of rocks on the floor of Jezero Crater, examined closely by NASA’s Perseverance rover, described a similar crystalline accumulation that forms as a thick body of magma that cools.The lead author sees a broader lesson in this finding. “Mars could sustain large, long-lived systems where molten rock evolves and reprocesses itself throughout the entire crust,” McKay-Champion said.These seismic boundaries spread across much of Mars’ northern hemisphere. If the team is right, the lighter molten material squeezed out of that deeper layer would have risen toward the surface over time. Study of paler, silica-rich rocks elsewhere on Mars suggests that some of those rocks have already reached the surface.These deep magma systems are related to how the planet builds its atmosphere and holds its water, conditions that could keep the world warm enough for life.
The ground shows the link.This type of recycling helps maintain climate stability over billions of years, and researchers have long linked the whole process to plate tectonics. Now, according to Professor John Wade, an Earth scientist at Oxford University who worked on the study, the Martian findings challenge those assumptions. Because the floor is now an ancient magma system that ran through the entire Martian crust without moving a single plate.One of the big questions in planetary science is whether Earth is unique. With this finding, scientists are now motivated to look more seriously at smaller, quieter worlds they once ignored.
