Before InSight discovered Marsquakes, seismic shocks had been directly observed only on the Moon.
In 2019, NASA’s SEIS seismometer installed on Mars by the InSight lander recorded the first seismic event on the Red Planet. Since then, the instrument has detected more than 500 marsquakes and made other massive discoveries.
Recently, the SEISS seismometer completed its first full year of data. That is, it worked during each day of the last Martian year. Apart from hundreds of marsquakes, data results revealed some unexpected surprises.
The following list of important facts summarizes all that has been achieved and discovered by InSight, including previous scientific results.
10 important things you should know about Marsquakes
1. Since the first registration of the “Marsquake” in April 2019, the instrument has recorded more than 500 such events, and their maximum magnitude has never been more than 4, which is unusual.
2. Scientists offer two versions of what is happening: either Mars is a seismically quieter planet than previously thought, or this is only a temporary period.
3. The frequency of such events was also unusual. Since April 2019, their number grew and soon the seismometer began to register tremors every day, but at the end of June 2020, there were practically no registered cases. For example, SEIS detected only five seismic events in September 2020.
4. The researchers speculate that the change of seasons may be to blame, due to which strong winds, which create small fluctuations in the planet’s surface layer, interfere with the operation of the instrument, which has very high sensitivity.
5. Another interesting fact was the absence of cases of detection of surface seismic waves on Mars. To date, only P-waves and S-waves propagating in the inner layers of the planet have been recorded.
6. Despite detecting hundreds of marsquakes per year, researchers can rarely calculate the direction and origin of the seismic waves. This is because few have clear seismic phase arrivals.
7. In the rare cases when marsquakes could be traced, they came from one of the youngest geological structures on the Red Planet – Cerberus Fossae.
8. Scientists suggest that the SEIS seismometer needed some time before it could confidently distinguish between the types of vibrations, distinguish weak signals from rich and varied background noise, and be able to systematically characterize these new signals.
9. Yet, NASA researchers need to understand the noises on Mars completely before they could find the most accurate way of interpreting InSight’s data. Even the lander interferes with the recordings and scientists need to find a way to exclude its noise entirely.
10. Although the scientific mission itself is devoted specifically to the study of Mars, the results of its study will shed light on the geophysics of all terrestrial planets, including ours, and will also help in compiling mathematical models of possible geophysical processes on exoplanets.
Seismicity in the Solar System
Until marsquakes became a thing, seismic shocks have been directly observed only on the Moon – with the help of seismographs delivered there by the Apollo.
The first seismometer flew to Mars aboard the Viking landing probes in 1976, but the Viking-1 failed to bring this device into working order. The same device on the Viking-2 began to work, but it turned out that the very position of the device and its relatively low sensitivity did not allow obtaining real data – it reacted mainly to the vibrations of the probe itself and the wind.
There is evidence that it felt a shock in November 1976, but it is more likely that the device was triggered by a strong gust of wind.
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Sources:
• Banerdt, W., Smrekar, S., Banfield, D., Giardini, D., Golombek, M., Johnson, C., . . . Wieczorek, M. (2020, February 24). Initial results from the Insight mission on Mars.
• EurekAlert. (n.d.). Seismicity on Mars full of surprises, in first continuous year of data.
• Giardini, D., Lognonné, P., Banerdt, W., Pike, W., Christensen, U., Ceylan, S., . . . Yana, C. (2020, February 24). The
seismicity of Mars.
• Johnson, C., Mittelholz, A., Langlais, B., Russell, C., Ansan, V., Banfield, D., . . . Banerdt, W. (2020, February 24). Crustal and time-varying magnetic fields at the Insight landing site on Mars.
• Seismological Society of America. (2021, April 23). Seismicity on Mars Full of Surprises, in First Continuous Year of Data Collection.
