Ever looked at that tiny red dot in the sky and wondered what’s actually going on down there? It’s basically a rusted ball of rock, but once you start peeling back the layers, things get weird. Most of us grew up hearing it’s just a "Dead Earth," but recent data from 2025 and 2026—thanks to the tireless work of NASA’s InSight lander—shows it’s more like a "Lumpy Earth."
Honestly, the planet is a mess.
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If you want to know mars what is it made of, you have to think of it as a giant, cosmic jawbreaker. It has a crust that’s thicker than it has any right to be, a mantle that’s filled with ancient "shards" from its violent birth, and a core that we finally realized isn't just a pool of liquid metal.
The Red Dust and the Crustal "Lid"
The surface is what everyone knows. It’s red. But it’s not red because the rocks are naturally that color; it’s red because the iron in the dust has literally rusted. You’ve got a planet-sized case of oxidation. Basically, the Martian soil—or regolith—is a mix of volcanic basalt rock and a heavy dusting of iron oxide.
Beneath that rust, the crust is surprisingly thick. On Earth, our crust is broken into plates that slide around, but Mars is a "one-plate" planet. It has a "stagnant lid." This means the heat gets trapped inside because the crust doesn't move. According to InSight’s seismic data, the crust is somewhere between 15 and 47 kilometers thick. That’s a lot of rock just sitting there.
Why the Mantle Is Like a "Rocky Road" Brownie
For a long time, we thought the inside of Mars was smooth. Like a perfectly layered cake.
We were wrong.
Recent studies published in Science in late 2025 describe the Martian mantle as a "Rocky Road" brownie. Instead of a smooth, uniform flow of rock, it’s studded with giant chunks of material—some 4 kilometers wide—that are leftovers from when the planet first formed.
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The Composition of the Deep Rock
- Silicates: Just like Earth, the mantle is mostly silicate rock.
- Iron and Magnesium: It’s way richer in iron than Earth's mantle is.
- The "Shards": These are chemically distinct fragments of the early crust that got sucked down during massive impacts 4.5 billion years ago.
Because Mars doesn't have plate tectonics to "stir the pot," these ancient shards haven't been melted down or smoothed out. They’re just... stuck there. It’s a planetary time capsule.
The Big 2025 Discovery: The Solid Heart
This is the part that’s currently shaking up the scientific community. For years, the consensus was that Mars had a completely liquid core. We thought it was just a big ball of molten iron, nickel, and sulfur.
But in September 2025, researchers re-analyzing seismic waves (specifically PKKP waves) found something hidden.
Mars has a solid inner core.
It’s about 600 kilometers in radius. That’s roughly 18% of the planet's radius, which—interestingly enough—is almost the same ratio as Earth’s inner core. This "hardened heart" is mostly iron and nickel, but it's likely got a surprising amount of oxygen mixed in.
The outer core remains liquid, a swirling mix of iron, sulfur, carbon, and hydrogen. This high sulfur content is actually why the core stayed liquid for so long; sulfur acts like an antifreeze, lowering the melting point of the iron.
The Air (Or Lack Thereof)
If you stood on Mars today, you’d notice the "air" is basically non-existent. It’s about 1% as thick as Earth’s atmosphere. You’d need a pressure suit just to keep your blood from boiling, not just for oxygen.
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It’s almost entirely Carbon Dioxide ($CO_2$). We’re talking 95%. The rest is a bit of Nitrogen, some Argon, and tiny traces of Oxygen. Because the atmosphere is so thin, it can’t hold onto heat. That’s why the average temperature is a bone-chilling -62°C.
What This Means for Future Explorers
So, if you’re planning a trip, what does this composition actually offer?
Honestly, it’s a goldmine of raw materials, but you’ve got to work for them. The abundance of iron and silicates means we can potentially 3D-print habitats using the Martian soil. The discovery of boron in Gale Crater and hydrated minerals (like clays) suggests that water is locked up in the rocks themselves.
The biggest takeaway from the 2025-2026 data is that Mars is far more complex than a "dead" rock. It has a structured, lumpy interior that tells the story of every asteroid that ever hit it.
Actionable Insights for Mars Enthusiasts
- Follow the InSight Data: While the lander itself is retired, the "seismic graveyard" of data it left behind is still being decoded. Watch for more papers in Nature regarding the core-mantle boundary.
- Monitor Methane Spikes: If you're interested in life, keep an eye on the Curiosity rover's methane readings. Methane on Mars often comes in "burps," and we still don't know if that's geological (serpentinization) or biological.
- Look into In-Situ Resource Utilization (ISRU): This is the tech that will turn Martian CO2 into oxygen and Martian soil into bricks. It's the most practical application of knowing what the planet is made of.
Mars isn't just a destination; it's a 4.5-billion-year-old puzzle that we're only now starting to piece together. The solid core discovery changes how we think about its lost magnetic field, and the "lumpy" mantle shows us a world that refused to grow up and move its tectonic plates. It's a frozen moment in solar system history.