Mars chilled for aeons, but stayed so stressed it gets crusty marsquakes

Mars doesn’t have tectonic activity but still manages to have marsquakes, according to a paper that probed a 2022 shake detected by the InSight lander.

As explained in a Geophysical Research Letters paper titled A Tectonic Origin for the Largest marsquake Observed by InSight, in May 2022 the InSight lander detected the strongest rumble it observed during its working life.

Previous such incidents of this sort were correlated to objects hitting Mars. Mars boffins therefore examined data gathered by seven orbiters resident around the red planet in the hope of finding evidence, but could not find evidence suggesting an extramartian origin for the shake, which is known as “S1222a”.

“We undertook a comprehensive search of the region in which the marsquake occurred,” the paper states, but “did not identify any fresh craters in the area, implying that the marsquake was likely caused by geological processes.”

Mars, however, is thought not to have active tectonic plates, the source of earthquakes down here on Terra.

Lead author Dr Benjamin Fernando, a postgraduate fellow the University of Oxford’s Department of Physics, suggested the quake “was likely caused by the release of stress within Mars’ crust.”

“These stresses are the result of billions of years of evolution; including the cooling and shrinking of different parts of the planet at different rates,” Fernando opined. “We still do not fully understand why some parts of the planet seem to have higher stresses than others, but results like these help us to investigate further.”

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The paper explains that the region where the quake was detected displays signs of “wrinkle ridges”, a feature that forms when tectonic forces compress a lava sheet that’s not yet set rock hard. The region also shows signs of “enhanced avalanche rates”, which the paper rates as “potentially indicative of surface-wave induced shaking”.

The region is also dusty, so a meteor whacking it would likely leave abundant evidence. Nor did spacecraft spot a dust cloud that would suggest a hidden impact zone.

“These lines of reasoning lead us to conclude with a high level of confidence that the S1222a event was not associated with a meteoroid impact event,” the paper concludes. “The only explanation which is consistent with current observations is a subsurface tectonic source.”

Dr Fernando suggested “One day, this information may help us to understand where it would be safe for humans to live on Mars and where you might want to avoid!”

Oxford’s article about the paper includes quotes from Chinese, European, and Dhabyani scientists, all chuffed to have been able to collaborate.

Dr Daniela Tirsch, science coordinator for the High Resolution Stereo Camera on board the European Space Agency’s Mars Express Spacecraft said: “This experiment shows how important it is to maintain a diverse set of instruments at Mars” – fair comment given that Mars InSight has been retired, without a replacement in prospect. ®