Mars' Grand Canyon Is Still Cracking: A Marsquake Reveals Active Faults
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Mars is often described as a dead planet: cold, dry and geologically quiet. A study published on 15 October 2026 in Nature Communications says that is not the whole story. Using a Valles Marineris marsquake recorded years ago, scientists showed that faults beneath the largest canyon in the solar system are still slipping today.
Valles Marineris in numbers
Valles Marineris is a network of canyons that runs nearly 3,900 km across Mars, reaches up to 600 km wide and drops more than 9 km deep. Put on Earth, it would stretch roughly from New York to Los Angeles.
Compared with the Grand Canyon, it is about nine times longer and about five times deeper. It formed billions of years ago as the Martian crust split apart near a huge volcanic region called Tharsis.
The quake that gave it away
NASA's InSight lander carried the first seismometer ever placed on Mars. Between 2018 and the end of its mission in December 2022, it recorded more than a thousand marsquakes.
One of them, catalogued as S0976a, was recorded on 25 August 2021, InSight's 976th Martian day. Earlier work had placed it near western Valles Marineris, but nobody knew its cause. Researchers at Imperial College London and Columbia University went back to the data.
They analyzed the strength and arrival direction of different seismic waves to reconstruct how the ground moved at the source. Their conclusion: a fault slipping roughly 20 to 40 km below the surface of western Valles Marineris.
Ruling out impacts and landslides
A shake on Mars is not automatically a fault. Meteorite impacts and landslides can produce seismic signals too, and Valles Marineris is lined with giant landslide deposits.
The team checked orbital images of the area for fresh craters or new slope collapses around the time of the quake. They found none. A deep fault was the best remaining explanation.
How can Mars have active faults without plate tectonics?
On Earth, most quakes happen where moving tectonic plates grind past each other. Mars has no moving plates. Its outer shell is one rigid piece.
The study suggests that ancient fractures, formed when the canyon opened billions of years ago, are still weak spots. Stresses inside the planet today, from its slowly cooling interior and the weight of the Tharsis volcanoes, find those old weak spots and make them slip. In other words, old scars still decide where the crust breaks.
Part of a bigger pattern
Valles Marineris joins a short list of places where InSight data show active faulting:
- Cerberus Fossae, a set of young fissures that produced many of InSight's strongest quakes
- Southern Elysium Planitia, the plains where InSight itself sat
- Valles Marineris, now confirmed
The different styles of faulting in these regions suggest stresses in the Martian crust vary from place to place.
Why this matters
Knowing where Mars still moves helps scientists understand how the planet's interior is cooling and evolving. It also matters for the future: any long-term base on Mars will want to know which regions are seismically quiet. And since the same quake also carried information about the planet's deep core, one recording has paid off twice.
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Frequently asked questions
Is Mars still geologically active?
Yes, in places. InSight recorded many marsquakes, and studies now link several to active faults, including beneath Valles Marineris.
How big is Valles Marineris?
About 3,900 km long, up to 600 km wide and more than 9 km deep.
What is marsquake S0976a?
A quake recorded by NASA's InSight lander on 25 August 2021, now traced to a fault under western Valles Marineris.
How deep was the marsquake?
The study places it roughly 20 to 40 km below the surface.
Does Mars have plate tectonics?
No. Its crust is a single rigid shell, but old fractures can still slip under modern stresses.