Mars mantle holds fragments from ancient giant impacts study finds

Mars mantle holds fragments from ancient giant impacts study finds
by Clarence Oxford
Los Angeles CA (SPX) Sep 01, 2025

Rocky material buried deep within Mars has been traced to colossal impacts 4.5 billion years ago, according to new findings from NASA's retired InSight lander. The discovery points to lumps of mantle rock, some up to 2.5 miles (4 kilometers) wide, scattered beneath the surface.

Scientists believe massive collisions melted large portions of early Mars into magma oceans while forcing fragments of impactors and Martian crust deep inside the mantle. Unlike Earth, where tectonic plate movement erases such features, Mars preserved them because its mantle circulates slowly.

"We've never seen the inside of a planet in such fine detail and clarity before," said lead author Constantinos Charalambous of Imperial College London. "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, features like these may well have been largely erased."

The study, published Aug. 28 in Science, analyzed eight marsquakes whose seismic waves slowed when passing through small regions of different composition inside the mantle. Computer models showed these anomalies matched the presence of rocky lumps left from giant impacts.

InSight placed the first seismometer on Mars in 2018 and recorded 1,319 quakes before its mission ended in 2022. By tracking how seismic waves traveled through the crust, mantle, and core, researchers uncovered evidence of these deep fragments.

"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," said Tom Pike, also of Imperial College London.

Unlike Earth, which has quakes tied to tectonic plates, Mars' tremors come from rock fractures and meteoroid strikes. The latter create seismic signals strong enough to reach the mantle. The altered wave patterns confirmed the presence of buried impact debris.

Charalambous compared the distribution of fragments to shattered glass, where large shards coexist with many smaller pieces. This pattern aligns with theories of a violent early solar system, when asteroids and protoplanets frequently struck young worlds.

Mars' sluggish interior motion has allowed these structures to remain intact for billions of years, offering a rare record of planetary evolution. Scientists suggest the Red Planet may serve as a window into the hidden interiors of other rocky planets lacking plate tectonics, such as Venus and Mercury.

The lumpy mantle structures revealed by InSight highlight how much remains to be learned from its seismic archive.

Research Report:Mars' ancient history and interior dynamics continue to emerge from InSight's unprecedented data.