Mars is built from the same materials as Earth, yet tells a radically different story
For the first time, humanity has listened to the heartbeat of another world and begun to understand its anatomy. NASA's InSight lander, stationed on the Martian surface, spent two years capturing the faint tremors of hundreds of Marsquakes, allowing international teams of scientists to map the red planet's interior layers with unprecedented precision. What emerged is a portrait of a world built from familiar materials yet shaped by a profoundly different destiny — a planet that formed early, cooled quickly, and never found the restless motion that has kept Earth geologically alive. In learning what Mars is made of, we have also begun to understand why it became so different from home.
- For the first time in history, scientists have mapped the interior of a planet other than Earth, a milestone that redraws the boundaries of planetary science.
- Mars's architecture defies prior assumptions: its crust is thinner than expected, its lithosphere nearly twice as thick as Earth's, and its liquid core far larger and lighter than models predicted.
- The presence of sulfur, carbon, oxygen, and hydrogen in Mars's molten core suggests the planet formed in the solar system's earliest moments, before lighter elements dispersed — a timing that may explain why Mars froze while Earth kept moving.
- The absence of plate tectonics on Mars, implied by its unusually thick lithosphere, points to a world that locked into geological stillness billions of years ago, never recycling or renewing its surface.
- Researchers acknowledge the model remains incomplete — more Marsquakes of varying types are needed — but the seismic foundation has been laid and the tools to decode planetary evolution now exist.
For the first time in human history, scientists have mapped the interior of another planet. The achievement belongs to NASA's InSight lander, which spent more than two years on the Martian surface listening for tremors. Its sensitive seismometer captured hundreds of Marsquakes — too faint to detect from Earth, but rich with information about what lies beneath the red planet's crust. International research teams have now published their findings, and the picture they've drawn is unlike anything geologists anticipated.
Mars shares Earth's basic architecture — crust, mantle, and core — but the details tell a radically different story. The Martian crust is thinner than previously believed, composed of two or three distinct layers. Above it, the lithosphere stretches roughly 500 kilometers deep, nearly twice the thickness of Earth's — a difference that suggests Mars never developed plate tectonics, the grinding motion of continental plates that has continuously reshaped our own world for billions of years.
At the planet's center lies a liquid core confirmed to be far larger than expected, with a radius of approximately 1,830 kilometers. It is also less dense than Earth's core, indicating the presence of lighter elements — sulfur, carbon, oxygen, and hydrogen — mixed into the molten iron and nickel. This composition carries a clue about Mars's origins: to have accumulated such lighter elements, the planet must have formed very early in the solar system's history, possibly while the primordial disk of gas and dust still existed. Earth formed later, after much of that material had dispersed, and the difference in timing may explain why one planet remained geologically restless while the other cooled into stillness.
Seismologist Sanne Cottaar noted that while Mars and Earth share the same building blocks, they look profoundly different — and having now mapped Mars's layers, scientists finally possess the tools to understand why. Researcher Brigitte Knapmeyer-Endrun acknowledged that more seismic data is needed to complete the model, but the foundation has been laid. For the first time, humanity has looked inside another world and begun to read its history.
For the first time in human history, scientists have peered inside another planet and mapped what they found. The achievement belongs to NASA's InSight lander, which has spent more than two years listening to Mars shake. Over that span, the spacecraft's sensitive seismometer picked up hundreds of Martian earthquakes—tremors too faint for human instruments on Earth to detect, but rich with information about what lies beneath the red planet's surface. International teams of researchers have now published their findings, and the picture they've drawn of Mars's interior is unlike anything geologists expected.
The data reveals that Mars is built from the same basic materials as Earth—a crust, a mantle, a core—yet the planet's architecture tells a radically different story. The Martian crust, it turns out, is thinner than scientists had believed, composed of two or three distinct layers rather than the thicker shell previously imagined. Above that sits the lithosphere, the rigid outer shell of the planet, which stretches down roughly 500 kilometers. That's nearly twice as thick as Earth's lithosphere, a difference that hints at a fundamental divergence in how the two worlds evolved. Mars, researchers believe, never developed plate tectonics—the grinding, recycling motion of continental plates that has shaped Earth's surface for billions of years.
Deeper still lies the mantle, structurally similar to Earth's but simpler: a single layer rather than the complex zones that characterize our own planet. And at the very center sits the core, which InSight's data has now confirmed is liquid and far larger than previously thought. With a radius of 1,830 kilometers, Mars's core is a vast sphere of molten metal, but it is less dense than Earth's core—a clue that it contains lighter elements mixed in with the iron and nickel. Sulfur, carbon, oxygen, and hydrogen all appear to be present in that molten heart.
This composition tells a story about Mars's birth. For the planet to have accumulated such a wealth of lighter elements in its core, it must have formed very early in the solar system's history, possibly while the primordial disk of gas and dust from which all planets coalesce still existed. Earth, by contrast, formed later, after much of that material had dispersed. The difference in timing may explain why the two planets took such divergent paths—why Mars cooled and locked into stillness while Earth remained geologically restless.
Sanne Cottaar, a seismologist involved in the research, noted that while Mars is built from the same building blocks as Earth, the planet looks profoundly different. Having now mapped the layers of Mars, scientists possess the tools to understand how that difference came to be. The seismic activity on Mars is sparse compared to Earth's constant rumbling, yet each tremor carries information encoded in the waves it produces. Brigitte Knapmeyer-Endrun, another researcher on the project, acknowledged that more data is needed—additional Martian earthquakes of different types will fill in gaps in the current model. But the foundation has been laid. For the first time, humanity has looked inside another world and begun to read its geology.
Notable Quotes
Mars is built from the same basic materials as Earth, but Marte looks very different. Now we have an image of the planet's layers that will help us understand how it formed.— Sanne Cottaar, seismologist
For Mars to have accumulated so many light elements in its core, it must have formed very early, possibly while the solar nebula still existed. Earth formed later.— Amir Khan, researcher
The Hearth Conversation Another angle on the story
How does listening to earthquakes tell you what's inside a planet?
Seismic waves travel through rock at different speeds depending on what the rock is made of and how dense it is. When InSight detects an earthquake, the waves bounce and refract through Mars's layers. By measuring how long those waves take to arrive and how they change, you can infer what's down there—like using sound to see through a wall.
So Mars has been shaking this whole time, and we're only now noticing?
Mars does shake, but far less than Earth. The earthquakes are smaller and less frequent. InSight's seismometer is extraordinarily sensitive—it can detect vibrations smaller than a grain of sand. Without that precision, we'd have heard nothing.
Why does it matter that Mars never had plate tectonics?
Plate tectonics is what keeps Earth geologically alive. It recycles material, drives volcanism, creates new crust. Mars locked up early. That tells us something about size, cooling rates, and how planets age. It's the difference between a world that stayed dynamic and one that froze.
The core being less dense—what does that mean for Mars?
It means Mars's core is contaminated, in a sense, with lighter stuff. That suggests Mars formed when the solar system was still young and chaotic, grabbing whatever was available. Earth's core is denser because it formed later, after the light elements had mostly burned off or drifted away.
Is there more to learn?
Absolutely. They need different types of earthquakes—ones that travel different paths through the planet. Right now they have a sketch. They need more detail to complete the picture.