Unprecedented quake on Mars wasn't caused by what you think

In May 2022, a potent temblor hit Mars.

The quake, at 4.7 magnitude, would cause dishes to rattle and a building's wooden frames to creak on Earth, but wouldn't be regionally catastrophic. Yet on Mars — a world much more geologically quiet — such an event is still considered a monster quake, at the limit of what planetary scientists would expect to record on the arid, desert world.

Since the temblor, scientists have poured over the event, recorded by NASA's InSight lander, its now-retired geologic probe. Some researchers supposed such a large quake came from a meteor slamming into Mars, as the planet is blanketed in meteor impacts. Yet new research, published in the peer-reviewed science journal Geophysical Research Letters, concludes that the source of the major marsquake came from deep inside the planet.

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Unlike Earth, Mars doesn't have erupting volcanoes or any molten rock brewing near the surface. It's unlikely to have any colossal structural, or tectonic, plates gradually moving around atop hot, circulating rock, which on Earth creates mountain ranges and triggers quakes.

Yet Mars may still have significant activity deep underground, as the planet's ancient rocky crust continues to evolve.

"We still think that Mars doesn’t have any active plate tectonics today, so this event 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," Ben Fernando, who researches planetary geophysics at the University of Oxford and led the new study, said in a statement.

A spectrogram from the InSight lander's recording of a large quake (shown on left) in May 2022. Credit: NASA / JPL-Caltech / ETH Zurich

Fernando and the research team used satellite imagery to scour the surface of Mars. They looked for a potential meteorite culprit that could have triggered such potent Martian shaking, receiving imagery contributions from the likes of the European Space Agency, the Chinese National Space Agency, and the Indian Space Research Organisation. They scrutinized the landscape for fresh impacts or dust clouds just after May 4, 2022.

None were found.

"We are willing to collaborate with scientists around the world to share and apply this scientific data to get more knowledge about Mars, and are proud to have provided data from the colour imagers on Tianwen-1 to contribute to this effort," Jianjun Liu, of the National Astronomical Observatories, Chinese Academy of Sciences, said in a statement.

NASA's dust-covered InSight seismometer on Mars' surface. Credit: InSight's seismometer

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NASA's InSight lander, which ran out of power in 2022, recorded over 1,300 marsquakes. In future missions, planetary scientists want to continue to probe Mars' interior and record quakes, improving our understanding of what's transpiring below the Red Planet's surface. There might even be places that are prone to relatively big quakes.

"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," Fernando said. "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!"