Mars interior filled with $4.5 billion-year-old mysterious rocks

Rocky material up to 2.5 miles (4 kilometers) across remains scattered in giant lumps below the Red Planet's surface.

The study by Imperial College London and NASA reveals what appear to be fragments from the aftermath of massive impacts on Mars that occurred 4.5 billion years ago.

The discovery was made thanks to NASA’s now-retired InSight lander, which detected the entities deep below the planet’s surface before the mission’s end in 2022.

NASA's Jet Propulsion Laboratory said: "The ancient impacts released enough energy to melt continent-size swaths of the early crust and mantle into vast magma oceans, simultaneously injecting the impactor fragments and Martian debris deep into the planet’s interior."

The findings, reported in a study published by the journal Science, offer clues about Mars’ interior and its ancient past.

The paper’s lead author, Constantinos Charalambous of Imperial College London, said: "We’ve never seen the inside of a planet in such fine detail and clarity before.

"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."

InSight, which was managed by NASA’s Jet Propulsion Laboratory in Southern California, placed the first seismometer on Mars’ surface in 2018. The extremely sensitive instrument recorded 1,319 marsquakes before the lander’s end of mission in 2022.

NASA add: "There’s no way to tell exactly what struck Mars: The early solar system was filled with a range of different rocky objects that could have done so, including some so large they were effectively protoplanets.

"They offer a record preserved only on worlds like Mars, whose lack of tectonic plates has kept its interior from being churned up the way Earth’s is through a process known as convection."