Marsquakes caused by meteorite impacts
On Earth, seismic data plays a crucial role in understanding the planet’s interior structure, tectonic activity and earthquake dynamics. Seismic waves on Earth are caused by earthquakes or human activities, such as explosions. Shifting focus to Mars, the use of seismic data provides a comparable method for exploration, though it comes with distinct goals and challenges. Recently, an international research team, led by institutions like ETH Zurich and Imperial College London, has applied seismic techniques to study Mars. The current rate of meteoroid impacts on Mars is crucial for determining accurate absolute ages of surfaces across the Solar System. In addition to this, it contributes to the understanding of the formation of the Solar System.
Meteoritic impacts can be classified such as we do with earthquakes on Earth. The impact of the meteorite creates seismic waves, when this happens on Mars it causes a marsquake. Quakes have been well-documented on the Moon and evidence suggests quakes on Venus. The first time marsquakes have been detected was by the Viking mission in 1976, at that time they were yet to be confirmed. In 2019 the InSight mission confirmed the detection of the marsquakes for the first time. The NASA Mars InSight mission is aimed to study the deep interior of Mars and was launched by NASA in 2018. InSight detects and analyses seismic waves that travel through the Martian crust and mantle. That meteorites can reach the Martian surface has to do with the relatively thin atmosphere, which provides circumstances for a burning meteorite to reach the surface.
Data of the InSight mission recently revealed a previously unknown class of marsquakes; very-high-frequency (VF) marsquakes. The VF’s marsquakes are characterized by, as the name shows, high-frequency signals and their short duration. The more typical and previously known marsquakes have different characteristics and are associated with tectonic activity or other geological processes. There is compelling evidence that Mars was more seismically active in the past, indicated by significant magnetic striping in southern Mars. On Earth, such striping is typically a sign of thin crust splitting and spreading, as seen in the Mid-Atlantic Ridge. However, no spreading ridge has been identified in this Martian region, suggesting an alternative, possibly non-seismic explanation may be necessary. The data of the InSight mission also shows that meteorite impacts occur on a daily basis on Mars. The daily meteorite impacts on Mars form craters of circa 8 meter in diameter. The larger measured impacts, ones that cause craters of circa 30 meters in diameter, occur on a monthly basis on the planet.
The counting of craters is a fundamental method used in planetary geology for determining surface ages. In general, regions with relatively few crater impacts are young and regions with relatively many crater impacts are old. When a meteorite impacts a planetary surface, it creates a crater. Over time, the number of craters on a surface accumulates. By comparing crater densities across different regions and correlating them with known ages of specific features scientists can construct a timeline of planetary surface evolution.
Crater counting has revealed that the Martian highlands are older, with heavy cratering, whereas the volcanic plains and regions like Tharsis are younger and less cratered. There are three important geological eras on Mars. The Noachian Period (about 4.1 to 3.7 billion years ago): characterized by heavy bombardment, resulting in a heavily cratered surface. Most of the highlands of Mars date back to this period. The Hesperian Period (about 3.7 to 3.0 billion years ago): marked by volcanic activity and the formation of large lava plains, which have fewer craters compared to Noachian terrains. And the Amazonian Period (about 3.0 billion years ago to present): includes the youngest surfaces on Mars, with relatively few craters. This period is also associated with ongoing volcanic and erosional processes.
