Unveiling the secrets of Mars' unique geology, research reveals that the Red Planet boasts a crust that is significantly thicker on average than those of Earth or the Moon. Furthermore, the primary heat source propelling Mars' geological activity is largely driven by radioactivity.
Marsquake Reveals the Thickness of Martian Crust
The most significant Marsquake observed to date in NASA’s Mars InSight mission last year has allowed ETH Zurich researchers to determine the thickness and density of the Martian crust. The data reveals that Mars’ crust is considerably thicker than Earth’s or the Moon’s, and that its primary heat source is radioactive decay.
Earth-Shaking Findings from a Martian Tremor
In May 2022, the Marsquake Service at ETH Zurich recorded a seismic event of an estimated magnitude of 4.6, the largest ever observed on another planet. According to Doyeon Kim, a seismologist at the Institute of Geophysics at ETH Zurich, this Marsquake sent out strong seismic waves that traveled along Mars’ surface.
Surface Waves Unlock a Global View of Mars
After over three years of monitoring, a significant Marsquake rewarded researchers with data that offered a comprehensive view of the planet. The seismic waves traveled around the planet multiple times, supplying local and global information about Mars.
Insights into Mars’ Global Structure
The researchers observed surface waves from this quake that circumnavigated Mars up to three times. The team measured their propagation speeds at different frequencies to glean information about the structure these waves traversed. “Now, we have seismic observations representing the global structure,” says Kim.
Measuring Mars Against Earth and the Moon
Combining new findings with existing data on Mars’ gravity and topography, the researchers determined the thickness of the Martian crust to average 42 to 56 kilometers. In contrast, seismic data indicates the Earth’s crust averages 21 to 27 kilometers in thickness, while the lunar crust is between 34 and 43 kilometers thick.
Unveiling the Martian Dichotomy
The research also addressed the long-observed contrast between Mars’ northern and southern hemispheres. Despite this dichotomy, the researchers found that the crust’s density in the northern lowlands and the southern highlands is similar, albeit the crust extends deeper in the southern hemisphere.
Decoding Martian Crust’s Radioactive Heat
The study also sheds light on Mars’ thermal history. As a single-plate planet, Mars’ primary heat source is the decay of radioactive elements such as thorium, uranium, and potassium. The researchers found that 50 to 70 percent of these heat-producing elements are in the Martian crust, potentially explaining the existence of regions where melting processes may still occur today.
The InSight Mission
The InSight (Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport) lander was a NASA mission that operated on Mars from November 2018 until its retirement on December 21, 2022. InSight was specifically designed to study the deep interior of Mars, a region that hadn’t been scrutinized before this mission. Unlike previous Mars missions that focused on the surface or atmosphere of the planet, InSight concentrated on the crust, mantle, and core.
Contributing to our understanding of Mars
InSight was equipped with a suite of scientific instruments, including a seismometer to detect marsquakes, a heat flow probe to measure the planet’s internal heat, and radio science experiments to study the planet’s rotation and interior structure. InSight provided invaluable insights into the evolutionary processes of rocky planets. Its mission ended after over four years of successful operation and scientific discovery, significantly contributing to our understanding of Mars and its geological history.
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