During its stay on the surface of Mars, NASA’s InSight apparatus, whose tasks included studying seismic activity, heat transfer, internal structure and composition of the Red Planet, recorded over 1,300 seismic events, known as marsquakes. The most powerful of them, magnitude 4.7 on the Richter scale, was recorded by InSight on May 4, 2022.
The event, designated S1222a, was similar to two marsquakes that occurred a year earlier and were caused by the fall of two meteorites. Craters measuring 100-200 meters in size, left at the site of these impact events, were expectedly found in previously predicted locations. According to the calculations of planetary scientists, for S1222a a crater with a diameter of more than 300 meters should have been located in the geologically active zone of the Cerberus Furrows, one and a half kilometers from the InSight landing site.
All countries that support the operation of their vehicles in Mars orbit were searching for a new crater or its traces in the form of a cloud of dust. After several months, the efforts of five space agencies found neither the crater itself, nor its traces, nor any candidates for the role of an explosion crater. An international group of scientists spoke about this in an article, published In the magazine Geophysical Research Letters.
The absence of traces of an impact event indicates a different nature of the origin of the S1222a marsquake, namely geological. And although, as the researchers suggested, on Mars, unlike Earth, there is no active plate tectonics, the seismic event could be caused by a release of stress within the Martian crust. Such stresses result from billions of years of evolution, cooling and contracting of different parts of the planet at different rates.
Nevertheless, the results of the new work, more precisely, the likely connection of the most powerful recorded Marsquake with a subsurface source, indicate that the planet is much more seismically active than previously thought. In subsequent work, scientists plan to study in more detail the potential subsurface tectonic sources that could provide this event. According to the authors of the work, one day this information could help people understand where it will be safe to live on Mars, and which places are best avoided.
Seismograms of event S1222a and two confirmed events S1000a and S1094b caused by a meteorite / © Fernando B., et al., Geophysical Research Letters2023
The question of the presence of geological activity on the fourth planet has another side. If there is one there, then the temperature of the Martian interior may be higher than what was previously modeled. And if the surface of Mars is warmer than expected, this could also explain the presence of large subglacial lakes near its south pole.
The very existence of these objects, discovered just a few years ago, is constantly being questioned, including on the grounds that the estimated temperature under the Martian surface is too low. If it is actually higher, underground reservoirs may not only be located under the poles. And it is possible that they are potentially suitable for simple life.
Unfortunately, Marsquake S1222a was one of the last events recorded by InSight before the end of the mission was announced in late December 2022. The fact is that the solar panels of the device, which were its only source of energy, became covered with a thick layer of dust during four years of operation on the surface of Mars and ceased to generate enough electricity for research. During the mission, InSight compiled a detailed diagram of the subsurface layers of the Red Planet, estimated the size of its core, and identified the seasonality of marsquakes, linking some of them with meteorite falls, and others with the geological features of this celestial body.
