The Earth’s mantle is dynamic, shifting and recycling – albeit very slowly, over vast geological timescales – thanks to the presence of active plate tectonics. In contrast, Mars’ mantle is relatively stagnant. Locked inside a single layer of crust, it provides a “time capsule” with clues to its primeval past.
Scientists writing in the journal Science lifted the lid on Mars’ crust to reveal its chunky interiors and evidence of its chaotic history. The Martian mantle is less smooth, even layers and more uneven clumps scattered haphazardly throughout its core, like Rocky Road. These clumps are the result of violent collisions with meteorites billions of years ago.
“What we are seeing is a ‘fractal’ distribution, which happens when the energy from a cataclysmic collision overwhelms the strength of an object,” Professor Tom Pike from the Department of Electrical and Electronic Engineering at Imperial College London said in a release. “You see the same effect when a glass falls onto a tiled floor as when a meteorite collides with a planet: it breaks into a few big shards and a large number of smaller pieces.”
A Rocky Past for Mars
Mars, Earth and the other rocky planets were forged some 4.5 billion years ago from dust circling the Sun. In the first tens of millions of years of the Solar System’s history, these rocky planets faced a series of extreme crashes with vast, planet-sized bodies – events that released so much energy, parts of the planets melted, creating large oceans of magma.
“As those magma oceans cooled and crystallized, they left behind compositionally distinct lumps of material – and we believe it’s these we’re now detecting deep inside Mars,” Constantinos Charalambous from the Department of Electrical and Electronic Engineering at Imperial College London explained in the release. "The fact that we can still detect its traces after four and a half billion years shows just how sluggishly Mars' interior has been churning ever since."
Read More: Wave Ripples Prove the Existence of Ice-Free Lakes on Ancient Mars
Time Capsule in the Mantle
The mantle is the layer that exists between the crust and the core. Whereas Earth’s is dynamic and changing, Mars’ is not – meaning it is far more likely to provide insights into the planet’s early history.
Using data collected by NASA’s InSight mission, the researchers analyzed seismic signatures of eight marsquakes moving through the mantle. They found that the seismic waves with higher frequencies were slower to reach sensors from the impact site, suggesting some degree of interference.
These signs of interference are “consistent with a mantle full of structures of different compositional origins,” said Charalambous in the release – which can be thought of as “leftovers from Mars’s early days.” These “structures” – some 2.5 miles (4 kilometers) wide – are thought to consist of early crust and mantle, as well as debris from meteorites and other colliding bodies.
"What happened on Mars is that, after those early events, the surface solidified into a stagnant lid," Charalambous said in the release. "It sealed off the mantle beneath, locking in those ancient chaotic features — like a planetary time capsule."
Mercury, Venus and Beyond
The implications of this research extend beyond the Red Planet and may even offer a blueprint of sorts to the evolution of other terrestrial planets, like Venus and Mercury. The Earth’s geological records remain “elusive,” the study’s authors wrote, whereas the preservation of Mars’s ancient mantle provides “an unprecedented window into the geological history” of other rocky planets with an inactive crust.
They added: “This evolution holds key implications for understanding the preconditions for habitability of rocky bodies across our Solar System and beyond.”
Read More: NASA's Crewed Mars Mission in the 2030s Could Unlock Some Geologic Mysteries
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
