The largest meteorite impact ever recorded on Mars provides unexpected details about the planet’s interior structure

The largest meteorite impact ever recorded on Mars provides unexpected details about the planet's interior structure

In December 2021, a meteorite impacted the surface of Mars, creating powerful seismic waves on the planet’s surface. That was enough for the InSight mission’s seismometer. Analysis of these seismic waves has made it possible to establish the structure of the Martian crust on a large scale for the first time.

On December 24, 2021, a major EarthquakeEarthquake Mars was shaking the surface, and this phenomenon was immediately detected and recorded Seismometer of the Insite mission, is placed on the surface. Soon, the appearance of this tremor intrigues scientists, because the red planet does not exist Tectonic platesTectonic plates, Very rarely produces large earthquakes. In fact, earthquakes have nothing to do with the planet’s intrinsic geological phenomenon. It would have been caused by a meteorite impact on the surface, a hypothesis confirmed by the study MROMRO In orbit around the planet reveals a new crater with a diameter of 150 meters!

For scientists, this kind of phenomenon is simply unexpected. Because the force of the impact created a specific type of wave that propagated across the surface. The characteristics of these waves, which have never been detected on Mars before, enabled us to study the structure of the Martian crust in its entirety.

Listen to the meteorite impact on Mars recorded by the Inside Lander. © NASA, JPL-Caltech, CNES, Imperial College London

Very special waves that make it possible to study the surface of Mars

surface waves In fact, very special waves occur on Earth during strong earthquakes. For this reason, they have not been seen before on Mars, which produces only low-level earthquakes. Although these waves only propagate at the surface, they transmit most of the earthquake’s energy. On Earth, they are especially feared because they cause so much damage.

Unlike waves BlocksBlocks (B and S), The SpeedSpeed Surface waves depend on them frequencyfrequency. However, lower frequencies are more sensitive to larger depths. This is an interesting feature for studying the Martian crust. For the first time, measurement of the dispersion of these waves has made it possible to directly observe the variations in velocity as a function of depth and create a complete picture. The crustal structure of Mars.

The meteorite impact dug boulder-sized chunks of ice from the Martian surface. The existence of ice so close to the surface has scientists wondering and questioning. An overview of the affected area created from images captured from space by the MRO probe. © NASA, JBL-Caltech, University of Arizona

The crustal structure of Mars, for the first time on a large scale

such as Earth’s crustEarth’s crustThe Martian crust shows major variations in topography, thickness, and age, but is alternately affected by craters, erosion, and cratering. VolcanoVolcano. The crust of Mars presents an important differenceNorthern HemisphereNorthern Hemisphere And thisSouthern HemisphereSouthern Hemisphere, the origin of which remains highly debated. A dichotomy characterized by a topographic difference of about five kilometers. The southern part, which is higher, shows a more concave surface compared to the northern surface, which is characterized by wide plains.

The SeismometerSeismometer Insight has so far made it possible to better control the thickness of the crust in the area where it is located (Elysium Planitia), i.e. 39 +/- 8 km. Despite the importance of this result, it is only a specific point and the Martian crust, as a whole, is largely unknown. However, the meteorite impact made it possible to create a universal model. Analysis of surface waves has enabled scientists to study the structure of the crust up to a depth of 30 kilometers below the surface.

A precursor uniform crust between north and south

The results were published in the journal Science, the Martian crust reveals a relatively uniform structure between the meteorite impact site and the insite location. Overall, the crust has a higher density than suggested by observations made at the level of the seismometer. The crust beneath Insite appears to be actually less dense and may have been formed by a large meteorite impact 3 billion years ago. However, it appears that this part of the Martian crust is not representative General crustal structure of Mars.

The study suggests that the northern and southern crusts may be relatively similar in composition or structure, contrary to previous theory regarding the bifurcation of Mars. Variations in density may explain this perception of difference in crustal thickness. The origin of the bifurcation is still debated and may be linked to significant meteorite impacts, or a irregularityirregularity In ConvectionConvection from CodeCodeor a combination of the two processes.

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