We have long imagined Mars as a world that has finished its work—a planet of dust and silence, its mountains built, its canyons carved, its interior cooled into stillness. The images returned by rovers and orbiters show a landscape of ancient scars, a place where the geological clock has wound down. But a new study suggests that beneath the vast canyon system of Valles Marineris, something is still moving. The planet, it seems, has not entirely stopped speaking .
Researchers at Imperial College London and Columbia University have found direct seismic evidence that a marsquake detected by NASA's InSight lander originated beneath Valles Marineris, the largest canyon system in the solar system. The event, recorded on August 25, 2021, was caused by rocks sliding sideways along a fault roughly 20 to 40 kilometers beneath the surface . The findings were published in Nature Communications.
Valles Marineris is difficult to hold in the mind's eye. It stretches nearly 3,900 kilometers across Mars, reaches up to 600 kilometers wide, and plunges more than nine kilometers deep—nearly nine times longer, more than twenty times wider, and about five times deeper than the Grand Canyon . It was formed billions of years ago, likely by tectonic forces associated with the Tharsis volcanic region, and has long been considered a relic of a more active past.
The marsquake, designated S0976a, was unusual. It came from the opposite side of the planet from the InSight lander and was the only event during the mission that could be located in Mars' western hemisphere . Previous work had placed it near western Valles Marineris, but the cause remained uncertain. On Mars, seismic signals can come from meteoroid impacts, landslides, or other processes. The team tested those alternatives and found they could not reproduce the observed seismic waves. Satellite images of the source region showed no fresh crater or large landslide .
The best explanation was a strike-slip event, in which blocks of crust move horizontally past one another along a steep, deeply rooted fault. The orientation of the faulting matches what scientists would expect if ancient structures, established billions of years ago, were slipping again today under stresses from the planet's long-term cooling and the nearby Tharsis volcanic region .
Mars does not have plate tectonics like Earth. Its outer shell behaves as a single, slowly cooling lid. The finding that ancient faults can remain weak enough to rupture under present-day stresses is significant not only for understanding Mars but for understanding how other seemingly inactive planetary bodies might behave . "It shows that on a planet without plate tectonics, structures created billions of years ago can remain important and still control where the crust breaks today," said co-author Folarin Kolawole of Columbia University .
The InSight mission ended in 2022, its solar panels coated with dust, but its data continues to yield insights. The marsquake beneath Valles Marineris adds to a growing list of regions where active faulting has been detected on modern Mars, including the Cerberus Fossae fissures and southern Elysium Planitia. The stresses within the Martian crust, it appears, do not follow a single pattern.
Valles Marineris is not a dead landscape. It is a place where the planet's ancient architecture still shifts and settles, generating quakes that no human ear will hear but that instruments can record. Mars is quieter than Earth, but it is not silent.
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Sources: Lamont-Doherty Earth Observatory, Imperial College London, Nature Communications, Universe Today
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