(NASA)
German scientists working with the seismograph SEIS of the Martian station InSight have published new results of the analysis of data collected over two Martian years.
They were able to identify periodic changes in the frequency of Marsquakes.
They are associated with the declination of the Sun, solar tides and the cycle of carbon dioxide on the planet.
Temporary changes in seismic activity on planets cannot be considered unusual. Moon activity is associated with the movement of the Moon around the Earth.
Some deep seismic sources are active near the perigee or apogee of the orbit, while others are active in orbital nodes.
In the case of the Earth, variations in the frequency of earthquakes are also observed, in particular, the annual seismic cycle in Nepal with a maximum from January to March is associated with the summer monsoons in the Ganges region.
The seismic activity of Mars is not associated with precipitation (it doesn’t rain on Mars).
However, it may depend on tidal forces from the Sun and Phobos, daily fluctuations in atmospheric pressure or seasonal changes in weather conditions.
A group of planetary scientists led by Martin Knapmeyer of the DLR Institute for Planetary Research has published the results of an assessment of the seasonality of seismic activity on Mars.
They were made on the basis of data obtained by the seismograph SEIS of the automatic station InSight, which has been operating on Mars for two years.
The goal of the scientists was to determine the dependence of the frequency of high-frequency seismic events recorded by the device on the observation time, which could provide information about possible sources of tremors.
A total of 415 events recorded from February 2019 to August 31, 2020 were analyzed.
The frequency of seismic events at the maximum, which was reached near the aphelion of the orbit of Mars, ranged from 3.5 to 4.5 events per day, the base frequency was 0.5 events per day.
Scientists came to the conclusion that Phobos did not cause changes in the frequency of the investigated Marsquakes, as well as falls of meteoroids or annual changes in wind strength.
Instead, the most likely factor in changing the frequency of Marsquakes may be the declination of the Sun and annual solar tides.
At the same time, the CO2 cycle (the sublimation of ice and its subsequent deposition and accumulation on the planet's surface during the Martian year) is the least likely factor affecting the seismic activity of the planet.
The physical mechanism of how the solar illumination of the surface of Mars is associated with the sources of Marsquakes remains to be determined.
This may be due to thermal shock and the rate of erosion of rocks, avalanches, or, less likely, landslides or other processes.
To understand this and refine theoretical models, researchers need more observational data and reliable cases of detecting sources of seismic activity.
Sources:
- Earth and Planetary Science Letters: https://www.sciencedirect.com/science/article/pii/S0012821X2100426X?via%3Dihub#br0360