When you picture the inside of a planet, it’s easy to imagine smooth, tidy layers stacked one on top of another.
For years, that’s exactly how scientists described Mars—like a clean slice of dessert with a crust, mantle, and core stacked neatly, much like a Millionaire’s Shortbread.
But fresh research has turned that image upside down.
Instead of being well-organized, Mars’ interior looks more like a chaotic mix.
And the best comparison? A Rocky Road chocolate bar, complete with chunky bits scattered throughout.
NASA’s InSight Reveals a “Chunky” Mars
Thanks to seismic data collected by NASA’s InSight lander, researchers at Imperial College London discovered that Mars is far from uniform on the inside.
Huge rock fragments, some stretching up to 2.5 miles (4 km) across, are scattered through the planet’s mantle—similar to the marshmallows and biscuits you find in a Rocky Road.
These ancient chunks, preserved like geological fossils, date back to Mars’ violent beginnings more than 4.5 billion years ago.
A Violent Start to the Red Planet
Mars didn’t have an easy childhood. After forming from dust and rock around the young Sun, the planet was struck by massive, planet-sized objects in a series of near-catastrophic impacts.
Dr. Constantinos Charalambous, lead researcher, explained that these collisions released so much energy that large parts of Mars melted into giant oceans of magma.
As those oceans cooled, they solidified into uneven chunks of material that became trapped deep inside the planet.
It’s these fragments that scientists are now able to detect—locked away for billions of years like a planetary time capsule.
Why Mars Stayed “Stuck in Time”
Unlike Earth, where tectonic plates and volcanic activity constantly churn the interior, Mars’ crust eventually solidified into what experts call a “stagnant lid.”
This sealed the planet’s outer surface and stopped the mantle from shifting much.
That sluggish movement is exactly why those early fragments are still intact.
As Dr. Charalambous put it, “The fact that we can still detect traces after four and a half billion years shows just how slowly Mars has been churning inside.”
A Cosmic Shattering Pattern
The fragments inside Mars aren’t randomly scattered—they follow a striking pattern.
A few very large chunks are surrounded by many smaller pieces, almost like what happens when a glass smashes on a tiled floor.
Professor Tom Pike, part of the research team, described this as a “fractal distribution.”
It’s the same effect you see when energy from a collision overwhelms the strength of an object—whether it’s a glass in your kitchen or a meteorite hitting a planet.
Clues to How Planets Are Born
For scientists, this discovery isn’t just about Mars—it could help unlock the secrets of how all rocky planets, including Earth, came to be.
Dr. Mark Panning of NASA’s Jet Propulsion Laboratory said the InSight mission has been transformative: “It’s exciting to see new discoveries made from the quakes we detected.
InSight’s data keeps reshaping how we think about planetary formation.”
Mars at a Glance
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Position: Fourth planet from the Sun
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Atmosphere: Thin, dusty, and cold
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Surface Features: Polar ice caps, canyons, extinct volcanoes, and signs of a more active past
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Day Length: Just over 24 hours
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Year Length: 687 Earth days
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Radius: 2,106 miles
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Moons: Phobos and Deimos
Despite its quiet appearance today, Mars’ interior tells a very different story—a violent past that still lingers beneath its frozen crust.
