For over four years, NASA's InSight lander has been collecting valuable data on Mars' interior through the use of seismic investigations. By analyzing the waves produced by marsquakes, scientists have gained insight into the structure and layers of the Red Planet. Recently, a meteor impact provided an opportunity for researchers to study the Martian crust in greater detail.
On December 24, 2021, InSight registered vibrations similar to a magnitude 4.0 marsquake. Satellite images later revealed a 150-meter-wide crater, confirming that a meteor had struck the planet. While meteor impacts on Mars are not uncommon, this particular event was significant because it was strong enough to produce surface waves. These waves, which travel through a planet's outermost layer, had never before been observed on a planetary body other than Earth.
Seismologists use seismic waves to study a planet's interior, much like doctors use X-rays to image the human body. As seismic waves pass through matter, their speed and energy change depending on the physical properties of the medium. By analyzing these changes, researchers can determine a planet's structure and composition. InSight's data has previously provided information on Mars' core and mantle, but the structure of the Martian crust has remained largely unknown.
The detection of surface waves offered a unique opportunity to study the Martian crust in more detail. Unlike body waves, which only sample a small portion of the crust directly beneath a seismometer, surface waves spread across the surface of a planet and interact with a wider area of the crust. Using data from the meteor impact, researchers were able to create an image of the Martian crust, revealing some surprising findings.
Previous studies using body waves suggested that the crust near InSight's equatorial location was porous and low in density. The impactor data confirmed this characterization, but also revealed that the crust in other areas was significantly different. In some regions, the crust was found to be much denser and less porous, indicating the presence of different geological processes at work.
The study, published in the journal Science, highlights the value of surface waves in understanding the structure of other planetary bodies. It also highlights the importance of continued exploration and research on Mars, as new discoveries continue to shed light on the mysteries of the Red Planet.
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