2023-05-27 09:00:00
Last year, the strongest earthquake ever observed on the red planet was captured by the Insight mission’s seismometer. If his magnitude of 4.6 on the Richter scale is up to today the largest ever measured on the planet or on other planets in the solar system, this earthquake has enabled scientists to obtain sometimes unpublished information on the structure and internal geology of Mars.
An earthquake bringing new information on the structure of planet Mars
This powerful earthquake (for the planet Mars), occurred on May 22, 2022 and might therefore be captured by the probes of the Insight mission, which completed its analyzes of the red planet last December following having persisted for 5 years. . Besides high magnitude, the waves from this earthquake also covered the entire Martian soil and circled the planet approximately 3 times before dissipating.
This made it possible to obtain complete seismic data of the entire planet Mars, which had not previously been possible. Indeed, the geological study of our neighbor was carried out until this earthquake via impacts of meteorites which provided precise but regional seismic data and which therefore did not allow to fully visualize the red planet.
By measuring the speed of propagation of the waves of the earthquake of May 22, 2022 on the planet at different frequencies, the scientists were able to obtain a global vision of the planet and an overview of its internal structure. Geologists have thus been able to estimate that the martian crust had a thickness of 42 to 56km on average. In comparison, the thickness of the Earth’s crust is on average 21 to 27 km and the thickness of the lunar crust of 34 to 43km.
This earthquake was also able to reveal that the northern hemisphere of Mars has a thinner crust than in its southern part. Until today, scientists thought that the difference in topography between the North and the South of the planet (martian dichotomy) was explained by a difference in the composition of the rocks of the two hemispheres, but this earthquake and the resulting data revealed that this was not the case, the Martian crust is simply much thicker in the southern hemisphere of Mars.
This discovery is very interesting and puts an end to a long-standing scientific discussion regarding the origin and structure of the Martian crust.
In addition to these differences in thickness of the Martian crust between its two hemispheres, strong contrasts might also be identified according to the region of the planet. Scientists were thus able to determine that the crust of the Red Planet was only only 10km at the impact basin of Isidis but that this thickness reached up to 90km in the province of Tharsis (near Mount Olympus, the highest volcano in the solar system).
Finally, the thickness of the Martian crust also says a lot regarding how the planet generates its heat as well as its thermal history. Mars does indeed have no tectonic activity, being a presumably single-plate planet. The main source of heat produced by the red planet is the disintegration of radioactive elements composing its rocks such as thorium, uranium, and potassium.
The data revealed that 50 to 70% of these heat sources are buried in the Martian crustwhich would explain why there are regions below the surface where rock melting (and therefore volcanic activity) is still active today.
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