SPACE/COSMOS
Mars’s interior more like Rocky Road than Millionaire’s Shortbread, scientists find
New research reveals the Red Planet’s mantle preserves a record of its violent beginnings.
image:
A giant collision in Mars’ early history created a global magma ocean and buried large fragments of debris deep within the young planet. As Mars cooled, it formed a solid crust — eventually becoming a stagnant lid that trapped heat and slowed the planet’s internal motion. Over billions of years, Mars’ interior evolved as slow convecting currents stretched, folded, and dismantled these ancient structures, leaving behind a jumbled interior filled with scattered remnants. These surviving debris — some large, but many more small and dispersed — form a geological time capsule, preserving clues to the planet’s earliest moments. Today, seismic waves from a much smaller, recent meteorite impact travel through this complex interior. By studying how these waves scatter and change, NASA’s InSight lander has revealed hidden details about the planet’s deep and turbulent past.
view moreCredit: Vadim Sadovski / Imperial College London
New research published in the journal Science reveals the Red Planet’s mantle preserves a record of its violent beginnings.
The inside of Mars isn’t smooth and uniform like familiar textbook illustrations. Instead, new research reveals it’s chunky - more like a Rocky Road brownie than a neat slice of Millionaire’s Shortbread.
We often picture rocky planets like Earth and Mars as having smooth, layered interiors - with crust, mantle, and core stacked like the biscuit base, caramel middle, and chocolate topping of a millionaire’s shortbread. But the reality for Mars is rather less tidy.
Seismic vibrations detected by NASA’s InSight mission revealed subtle anomalies, which led scientists from Imperial College London and other institutions to uncover a messier reality: Mars’s mantle contains ancient fragments up to 4km wide from its formation - preserved like geological fossils from the planet’s violent early history.
History of gigantic impacts
Mars and the other rocky planets formed about 4.5 billion years ago, as dust and rock orbiting the young Sun gradually clumped together under gravity.
Once Mars had largely taken shape, it was struck by giant, planet-sized objects in a series of near-cataclysmic collisions - the kind that also likely formed Earth’s Moon.
“These colossal impacts unleashed enough energy to melt large parts of the young planet into vast magma oceans,” said lead researcher Dr Constantinos Charalambous from the Department of Electrical and Electronic Engineering at Imperial College London. “As those magma oceans cooled and crystallised, they left behind compositionally distinct chunks of material - and we believe it’s these we’re now detecting deep inside Mars.”
These early impacts and their aftermath scattered and mixed fragments of the planet's early crust and mantle - and possibly debris from the impacting objects themselves - into the molten interior. As Mars slowly cooled, these chemically diverse chunks were trapped in a sluggishly churning mantle, like ingredients folded into a Rocky Road brownie mix, and the mixing was too weak to fully smooth things out.
Unlike Earth, where plate tectonics continuously recycle the crust and mantle, Mars sealed up early beneath a stagnant outer crust, preserving its interior as a geological time capsule.
“Most of this chaos likely unfolded in Mars’s first 100 million years,” says Dr Charalambous. “The fact that we can still detect its traces after four and a half billion years shows just how sluggishly Mars’s interior has been churning ever since.”
Listening into Mars
The evidence comes from seismic data recorded by NASA’s InSight lander - in particular, eight especially clear marsquakes, including two triggered by two recent meteorite impacts that left 150-metre-wide craters in Mars’s surface.
InSight picks up seismic waves travelling through the mantle and the scientists could see that waves of higher frequencies took longer to reach its sensors from the impact site. These signs of interference, they say, shows that the interior is chunky rather than smooth.
“These signals showed clear signs of interference as they travelled through Mars’s deep interior,” said Dr Charalambous. “That’s consistent with a mantle full of structures of different compositional origins - leftovers from Mars's early days.”
“What happened on Mars is that, after those early events, the surface solidified into a stagnant lid,” he explained. “It sealed off the mantle beneath, locking in those ancient chaotic features — like a planetary time capsule.”
Unlike the interior of Earth
Earth’s crust, by comparison, is always slowly shifting and recycling material from the surface into our planet’s mantle – at tectonic plates such as the Cascadia subduction zone where some of the plates forming the Pacific Ocean floor are pushed under the North American continental plate.
The chunks detected in Mars’s mantle follow a striking pattern, with a few large fragments - up to 4 km wide - surrounded by many smaller ones.
Professor Tom Pike, who worked with Dr Charalambous to unravel what caused these chunks, said: “What we are seeing is a ’fractal’ distribution, which happens when the energy from a cataclysmic collision overwhelms the strength of an object. You see the same effect when a glass falls onto a tiled floor as when a meteorite collides with a planet: it breaks into a few big shards and a large number of smaller pieces. It’s remarkable that we can still detect this distribution today.”
The finding could have implications for our understanding of how the other rocky planets - like Venus and Mercury - evolved over billions of years. This new discovery of Mars’s preserved interior offers a rare glimpse into what might lie hidden beneath the surface of stagnant worlds.
“InSight’s data continues to reshape how we think about the formation of rocky planets, and Mars in particular,” said Dr Mark Panning of NASA’s Jet Propulsion Laboratory in Southern California. JPL led the InSight mission before its end in 2022. “It’s exciting to see scientists making new discoveries with the quakes we detected!”
Journal
Science
Article Title
Seismic evidence for a highly heterogeneous Martian mantle
Article Publication Date
28-Aug-2025
Mars’ mantle is a preserved relic of its ancient past, seismic data reveals
Summary author: Walter Beckwith
Locked beneath a single-plate crust, Mars’ mantle holds a frozen record of the red planet’s primordial past, according to a new study of Martian seismic data collected by NASA’s InSight mission. The findings reveal a highly heterogenous and disordered mantle, born from ancient impacts and chaotic convection in the planet’s early history. “Whereas Earth’s early geological records remain elusive, the identification of preserved ancient mantle heterogeneity on Mars offers an unprecedented window into the geological history and thermochemical evolution of a terrestrial planet under a stagnant lid, the prevalent tectonic regime in our Solar System,” write the authors. “This evolution holds key implications for understanding the preconditions for habitability of rocky bodies across our Solar System and beyond.” A planet’s mantle – the vast layer that lies sandwiched between its crust and core – preserves crucial evidence about planetary origin and evolution. Unlike Earth, where active plate tectonics continually stirs the mantle, Mars is a smaller planet with a single-plate surface. As such, Mars’ mantle undergoes far less mixing, meaning it may preserve a record of the planet’s early internal history, which could offer valuable insights into how rocky worlds form and evolve. Using data from NASA’s InSight lander, Constantinos Charalambous and colleagues studied the seismic signatures of marsquakes to better constrain the nature of Mars’ mantle. By analyzing eight well-recorded quakes, including those triggered by meteorite impacts, Charalambous et al. discovered that high-frequency P-wave arrivals were systematically delayed as they traversed the deeper portions of the mantle. According to the authors, these delays reveal subtle, kilometer-scale compositional variations within the planet’s mantle. Because Mars lacks plate tectonics and large-scale recycling, these small-scale irregularities must instead be remnants of its earliest history. The scaling of Mars’ mantle heterogeneity suggests an origin in highly energetic and disruptive processes, including massive impacts early in the planet’s history, which fractured the planet’s interior, mixing both foreign and crustal materials into the mantle at a planetary scale. Moreover, the crystallization of vast magma oceans generated in the aftermath likely introduced additional variations. Instead of being erased, these features became frozen in place as Mars’ crust cooled and mantle convection stalled.
Journal
Science
Article Title
Seismic evidence for a highly heterogeneous Martian mantle
Article Publication Date
28-Aug-2025
No comments:
Post a Comment