June 19, 2021

NASA records more than 500 Martian earthquakes in a year


InSight mission seismometer.

InSight mission seismometer.

NASA’s InSight mission seismometer has collected its first continuous Martian year of data, revealing some surprises among the more than 500 earthquakes detected so far on Mars.

According to the balance, presented at the 2021 Annual Meeting of the Seismological Society of America (SSA), ‘Marsquakes’ are much smaller than earthquakes, with the largest event recorded at teleseismic distances around magnitude 3.6. The SEIS (Seismic Experiment for Interior Structure) seismometer is capable of detecting these small events because the background seismic noise on Mars can be much lower than on Earth, without the constant trembling produced by ocean waves.

“For much of a Martian year, from around sunset to the early hours, the Martian atmosphere becomes very calm, so there is no local noise either,” he explains. it’s a statement the member of the Savas Ceylan seismometer team from ETH Zürich. “In addition, our sensors are optimized and protected to operate in severe Martian conditions, such as extremely low temperatures and extreme daytime temperature fluctuations on the red planet.”

Martian earthquakes also come in two distinct varieties: low-frequency events with seismic waves propagating at various depths in the planet’s mantle, and high-frequency events with waves that appear to propagate through the crust. “In terms of how seismic energy decays over time, low-frequency events appear to be more like earthquakes” in which the shaking wears off relatively quickly, Ceylan said, “while high-frequency events resemble lunar earthquakes” by persisting for longer periods.

High frequency power

The vast majority of events are high frequency and occur hundreds of kilometers away from the lander. “It is not very clear to us how these events could be limited to high-frequency energy while occurring at such great distances,” He said. “On top of that, the frequency of those events appears to vary during the Martian year, which is a pattern we don’t know at all from Earth.”

Only a handful of seismic movements have clear seismic phase arrivals, the order in which different types of seismic waves arrive at a location, allowing researchers to calculate the direction and distance from which the waves are coming. All these seismic movements originate in a sunken area of ​​the surface called Cerberus Fossae, about 1,800 kilometers from InSight.

Cerberus Fossae is one of the youngest geological structures on Mars and may have formed from extensional faults or subsidence due to levee placement. Recent studies suggest that the spreading mechanism may be the source of the Cerberus Fossae earthquakes, Ceylan noted, “however, we have a long way to go in explaining the main tectonic mechanisms behind these earthquakes.”

The biggest challenge for the scientific team has been “adapt to unexpected signals in the data of a new planet”, Ceylan said. Although there were significant efforts to protect SIX from non-seismic noise by covering it and placing it directly on the Martian surface, your data is still tainted by the weather and lander noise. “We needed to understand the noise on Mars from scratch, find out how our seismometers behave, how the atmosphere of Mars affects seismic recordings, and find alternative methods to interpret the data correctly,” said Ceylan.

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