New research has revealed the chaotic, violent beginnings of Mars, uncovering that the planet’s interior is not the neatly layered world once imagined. Using data from NASA’s now-retired InSight lander, scientists have discovered that Mars’s mantle is filled with ancient, jagged fragments—some up to 4 km wide—left over from colossal impacts that occurred billions of years ago. The findings, published in the journal Science, show that the Red Planet’s deep interior is a geological time capsule, preserving a record of its tumultuous formation that would have been erased on a more active world like Earth.
Headline Points:
* “Rocky Road” Interior: The study found that Mars’s mantle contains preserved fragments of its early crust and debris from ancient impacts, giving the planet a “chunky” interior rather than a smooth, layered one.
* InSight’s Seismic Data: The discovery was made by analyzing how seismic waves from eight powerful “marsquakes” traveled through the planet’s interior, revealing anomalies that indicated a different composition from the surrounding rock.
* Geological Time Capsule: Unlike Earth, which recycles its crust and mantle through plate tectonics, Mars’s interior has been largely stagnant for billions of years, allowing these ancient fragments to be preserved.
* Evidence of a Cataclysmic Bombardment: Researchers believe these buried shards are the remnants of a period of intense asteroid and meteorite bombardment that was so energetic it melted large parts of the early planet.
* Implications for Planetary Science: The findings provide unprecedented insights into the early history of rocky planets and could help scientists better understand the formation and evolution of other stagnant worlds, like Venus and Mercury.
For four years, the InSight lander diligently recorded seismic activity on the surface of Mars, listening for “marsquakes” and the vibrations from meteorite impacts. The primary goal was to study the planet’s deep interior, including its core, mantle, and crust. While the mission concluded in 2022, the data it collected is still yielding remarkable discoveries.
This new analysis, led by scientists from Imperial College London, focused on the seismic signals from a handful of particularly clear marsquakes. When the seismic waves traveled deep into the mantle, the scientists noticed they were being subtly delayed and scrambled. This suggested the waves were passing through localized regions with a different composition than the rest of the mantle.
“What we’re seeing is a mantle studded with ancient fragments,” said Dr. Constantinos Charalambous, a planetary scientist who led the study. “Their survival to this day tells us Mars’s mantle has evolved sluggishly over billions of years. On Earth, features like these may well have been largely erased.”
The researchers believe these fragments are remnants of a period of heavy bombardment that occurred around 4.5 billion years ago, during the planet’s formation. These colossal impacts were so powerful they created “magma oceans,” melting vast swathes of the planet’s early crust and mantle. As the planet cooled, the molten material solidified, trapping large chunks of the original, fragmented material inside.
This is fundamentally different from what happens on Earth. Our planet’s powerful plate tectonics continuously churn its interior, recycling old material and erasing the scars of its early history. Mars, by contrast, has a single, rigid crust, a “stagnant lid” that has preserved its deep-seated history. The finding is a rare glimpse into a part of a planet’s history that has been a mystery for decades. It confirms that the chaotic processes of planetary formation leave behind lasting imprints and that some planets are much better at preserving their past than others.
