Mars’ Crust Unveiled: Latest Study Reveals a Structure Resembling a Thick Armor

by Klaus Müller
6 comments
Mars' crust density

Mars exhibits a striking contrast between its northern lowlands and southern high plains. Credit: MOLA Science Team

NASA’s Mars InSight mission made a breakthrough in its final year. Thanks to a massive marsquake, researchers from ETH Zurich were able to uncover the density and global thickness of Mars’ crust. Notably, the crust of Mars is considerably denser than that of Earth or the Moon, with radioactive decay being the primary source of the planet’s heat.

The Marsquake Service at ETH Zurich detected the most powerful marsquake ever recorded on a celestial body other than Earth in May 2022. This seismic event, with a rough magnitude of 4.6, was captured by the seismometer of NASA’s Mars InSight mission, stationed on the Martian surface.

Doyeon Kim, a seismologist from the Institute of Geophysics at ETH Zurich, describes how the marsquake generated robust seismic waves that journeyed across Mars’ surface.

Observations from the Epicenter

Three years of persistent monitoring eventually paid off when InSight’s seismometer recorded a substantial marsquake. The surface waves produced by this event provided a panoramic view of Mars, traversing not only from the quake’s epicenter to the measuring station but also around the entire planet multiple times.

Kim, who is also the lead author of a recent study published in Geophysical Research Letters, explains, “We tracked surface waves from the largest quake ever recorded during the InSight mission, which orbited Mars up to three times.”

The researchers analyzed the speed at which these waves travelled at different frequencies to gather data on the underlying structures.

Using these seismic velocities, insights were drawn on the internal structure at different depths. Prior observations from two large meteorite impacts also yielded regional findings along their unique propagation paths.

“Now we have seismic observations that represent the global structure,” Kim asserts.

A Comparative Analysis with Earth and Moon

By integrating their latest findings with existing gravity and topography data on Mars, the researchers determined that the Martian crust has an average thickness of 42 to 56 kilometers (26 – 35 miles). In contrast, Earth’s crust, based on seismic data, averages 21 to 27 kilometers (13 – 17 miles) thick, and the Moon’s crust, determined by the Apollo mission seismometers, is 34 to 43 kilometers (21 – 27 miles) thick.

“This implies that the crust of Mars is significantly denser than that of Earth or the Moon,” points out Kim. As a rule of thumb, smaller celestial bodies in our solar system usually have a denser crust than the larger ones. He elaborates, “Observing this quake was fortuitous. On Earth, estimating the crust’s thickness using a quake of the same magnitude as that on Mars would have been challenging. Despite being smaller, Mars transmits seismic energy more efficiently.”

A key discovery of this study relates to the contrasting northern and southern hemispheres of Mars, a feature visible since the advent of telescopes and clearly depicted in satellite imagery. Mars’ northern hemisphere is marked by flat lowlands, while the southern hemisphere is distinguished by high plateaus, a contrast termed the Martian dichotomy.

Assuming Equal Crust Density and Radioactive Heat

One could assume that this disparity stems from two different rock compositions, one denser than the other. However, while the rock composition might be consistent across Mars, the crust’s thickness varies, being thinner in the north and thicker in the south. Kim and his team have proven that the density of the crust in the northern lowlands and southern highlands is essentially the same, despite the southern crust extending deeper than the northern one.

“Our study also sheds light on how the planet generates heat and unravels Mars’ thermal history,” says Kim. As a single-plate planet, the predominant heat source within Mars arises from the radioactive decay of elements like thorium, uranium, and potassium. Up to 70% of these heat-generating elements reside in the Martian crust, explaining why some regions may still undergo melting processes today.

Reference: “Global crustal thickness revealed by surface waves orbiting Mars” by Doyeon Kim, Cecilia Duran, Domenico Giardini, Ana-Catalina Plesa, Simon C. Stähler, Christian Boehm, Vedran Lekic, Scott M. McLennan, Savas Ceylan, John Clinton, Paul McEwan Davis, Amir Khan, Brigitte Knapmeyer-Endrun, Mark Paul Panning, Mark A. Wieczorek and Philippe Lognonné, 22 June 2023, Geophysical Research Letters.
DOI: 10.1029/2023GL103482

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Frequently Asked Questions (FAQs) about Mars’ crust density

What major discovery did the final year of NASA’s Mars InSight mission yield?

The final year of NASA’s Mars InSight mission yielded a crucial discovery about Mars’ crust. A substantial marsquake allowed researchers to determine the density and thickness of the Martian crust globally.

How does the crust of Mars compare to that of Earth and the Moon?

The Martian crust is considerably denser and thicker than those of Earth or the Moon. The average thickness of the Martian crust is between 42 to 56 kilometers, while Earth’s crust averages 21 to 27 kilometers, and the Moon’s crust is 34 to 43 kilometers thick.

What is unique about the seismic activity on Mars?

The seismic activity on Mars is unique because, despite being a smaller planet, Mars transmits seismic energy more efficiently than Earth. Furthermore, the surface waves produced by a marsquake on Mars not only travel from the quake’s epicenter to the measuring station, but also around the entire planet multiple times.

What explains the differences between the northern and southern hemispheres of Mars?

The differences between the northern and southern hemispheres of Mars, known as the Martian dichotomy, are due to variations in crust thickness rather than rock composition. While the rock composition might be consistent across Mars, the crust’s thickness is thinner in the north and thicker in the south.

How does Mars generate its heat?

As a single-plate planet, Mars generates most of its heat from the decay of radioactive elements such as thorium, uranium, and potassium. Up to 70% of these heat-producing elements reside in the Martian crust, explaining why some regions may still be undergoing melting processes today.

More about Mars’ crust density

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6 comments

SpaceLover47 July 19, 2023 - 9:28 pm

This is so cool, always thought Mars was just a big red rock, but there’s a lot going on under the surface. thanks for sharing!

Reply
JoeD1991 July 19, 2023 - 10:06 pm

Wow, this is crazy! Mars crust is denser than Earth’s?! Who would’ve thought!

Reply
AstroGeek July 20, 2023 - 12:25 am

Is this why mars is red, because of the dense crust? so many questions… gotta read more about this.

Reply
ScienceFan101 July 20, 2023 - 12:40 am

It’s amazing how we can learn so much from something like a marsquake! Keep the good stuff comin!

Reply
PlanetEnthusiast July 20, 2023 - 6:29 am

always amazed by space stuff, did we have similar info about the moon’s crust? Or just earth and mars?

Reply
MartianDream July 20, 2023 - 6:38 am

Guess Mars is more complex than we thought. the radioactivity thing, thats interesting. i wonder if that has any effect on potential life forms out there.

Reply

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