Mars: A Rocky Road Beneath the Surface
We often imagine rocky planets like Earth and Mars as smooth, homogeneous layers consisting of the crust, mantle, and core. However, recent research reveals that Mars is more akin to a “rocky road” candy than a consistent piece of confectionery. This discovery is the result of efforts by scientists from Imperial College London and other institutions, based on seismic data from NASA’s InSight mission.
A History of Giant Collisions
Mars and other rocky planets formed about 4.5 billion years ago when dust and rocks orbiting the young Sun coalesced under gravity. After Mars largely formed, it experienced a series of catastrophic collisions with planet-sized objects, which are also believed to have formed Earth’s Moon.
Dr. Konstantinos Charalambous from the Department of Electrical and Electronic Engineering at Imperial College London stated, “These giant impacts released enough energy to melt large portions of the young planet into vast oceans of magma. As these oceans cooled and crystallized, they left behind distinctive chunks of material that we believe we are now detecting deep within Mars.”
Inside Mars
Seismic data recorded by the InSight lander revealed seismic oscillations that indicated disturbances deep within Mars. These disturbances were evidence of diverse structures within the mantle, indicating that Mars is not homogeneous but contains ancient chunks up to 4 kilometers wide.
This is similar to mixing ingredients in a “rocky road” candy, where different pieces of the crust and mantle distribute and leave varied chemical signatures. Unlike Earth, where tectonic plates constantly recycle the crust and mantle, Mars sealed early under a stagnant outer crust, preserving its interior as a geological time capsule.
Listening to Marsquakes
The evidence was based on seismic data recorded by InSight, especially eight clear marsquakes, including two caused by recent meteorite impacts. This data showed that high-frequency seismic waves took longer to reach sensors, confirming that the interior is not smooth but filled with different structures.
Dr. Charalambous remarked, “These signals show clear signs of interference as they travel through Mars’ depths, consistent with a mantle filled with structures of different compositional origins, remnants from Mars’ early days.”
Differences Between Mars and Earth
Mars’ interior differs significantly from Earth’s, where Earth’s crust is in constant motion, recycling material from the surface to the mantle, as seen in tectonic subduction zones. Mars retains large and small chunks in its mantle, following a pattern similar to “fractal” distribution, which occurs when the energy of a catastrophic impact exceeds the strength of a body, breaking it into large chunks and numerous smaller pieces.
Professor Tom Pike, who worked with Dr. Charalambous, noted, “What we see is a fractal distribution, and it’s amazing that we can still detect it today.”
Conclusion
This new discovery about Mars’ preserved interior offers a rare glimpse of what might lie beneath the surfaces of other stagnant worlds, such as Venus and Mercury. The data provided by InSight continues to transform our understanding of rocky planet formation, especially Mars. As Dr. Mark Banning from NASA’s Jet Propulsion Laboratory comments, “It’s exciting to see scientists uncovering new things using the detected marsquakes!”