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Rocky material from colossal impacts that struck Mars 4.5 billion years ago still lies buried deep within the planet’s mantle, offering new clues about its ancient history and inner structure.
Thanks to NASA’s now-retired InSight lander, scientists have uncovered evidence that giant lumps of rocky debris—some as large as 2.5 miles (4 kilometers) across—remain trapped in the Martian mantle. These fragments are thought to be remnants of massive collisions from the early solar system, when Mars was frequently bombarded by asteroids and even protoplanet-sized objects.
The findings, published in Science on August 28, reveal that the Martian mantle preserves these “time capsule” fragments far better than Earth, where plate tectonics and convection erase such features.
A Mantle Studded with Ancient Shards.
Lead researcher Constantinos Charalambous of Imperial College London explained:
“What we’re seeing is a mantle studded with ancient fragments. Their survival to this day tells us Mars’ mantle has evolved sluggishly over billions of years.”
On Earth, tectonic activity constantly recycles crust and mantle material, smoothing out ancient scars. But Mars, with its stagnant interior, has kept these relics intact—like shards of shattered glass frozen in place since the dawn of the solar system.
How InSight Made the Discovery.
NASA’s InSight mission, which operated on Mars from 2018 to 2022, placed the first seismometer on the planet’s surface. The instrument recorded 1,319 marsquakes, allowing scientists to study how seismic waves travel through the Martian crust, mantle, and core.
Researchers noticed that certain high-frequency seismic waves slowed and scrambled when passing through localized regions deep within the mantle. Simulations revealed that these disturbances matched the presence of dense, rocky lumps with different compositions than the surrounding mantle—likely remnants of those ancient impactors.
Marsquakes and Impact Evidence.
Mars lacks tectonic plates, so its quakes are triggered by either:
- Cracking of rocks due to stress and temperature changes.
- Meteoroid impacts, which send strong seismic waves deep into the planet.
Eight particular marsquakes showed clear seismic anomalies, pointing directly to these buried fragments. Scientists now believe the early impacts melted vast portions of Mars’ crust and mantle into magma oceans, where rocky debris was carried downward and trapped.
What It Means for Planetary Science.
This discovery not only changes how we view Mars but also helps scientists understand other rocky planets that lack tectonics—such as Venus and Mercury.
Co-author Tom Pike of Imperial College London said:
“We knew Mars was a time capsule bearing records of its early formation, but we didn’t anticipate just how clearly we’d be able to see with InSight.”
By studying Mars’ sluggish mantle and preserved impact fragments, scientists can glimpse the violent processes that shaped our solar system billions of years ago.
More About the InSight Mission.
- Managed by: NASA’s Jet Propulsion Laboratory (JPL) in California.
- Launched: 2018 under NASA’s Discovery Program.
- Partners: France’s CNES, Germany’s DLR, Switzerland’s ETH Zurich, UK universities, and Spain’s CAB.
- Instruments: Included the SEIS seismometer (to measure marsquakes) and the HP3 heat probe (to study subsurface properties).
Though InSight’s mission ended in 2022, its data continues to reshape our understanding of Mars’ interior—and by extension, the history of rocky planets across the solar system.