A single marsquake recorded by NASA’s retired InSight lander proves that the colossal canyon system Valles Marineris remains geologically active, with deep faults still slipping billions of years after their formation. The seismic event, designated S0976a, originated 20 to 40 kilometers beneath the western portion of the canyon, according to research published in Nature Communications.
Mars lacks moving tectonic plates, making the discovery of active fault movement unexpected. The planet’s exterior cools and contracts as a single stagnant shell, a process that normally allows ancient crustal fractures to heal and strengthen over time. Yet the new seismic analysis demonstrates that at least one deep fault beneath the vast Martian canyon has not sealed itself off from ongoing planetary stresses.
How a Single Seismometer Decoded a Far-Side Quake
InSight carried only one seismometer, and event S0976a struck on the opposite side of the planet at a distance of roughly 8,600 kilometers. Direct seismic waves failed to reach the lander in usable form. Instead, researchers tracked PP- and SS-waves, which are compression and shear waves that bounced once off the Martian surface halfway through their journey.
Jung-Hun Song of Imperial College London led the study alongside Doyeon Kim, also of Imperial, and Folarin Kolawole of Columbia University. The team modeled the wave trains against simulated interiors for Mars, testing every combination of fault orientation and depth down to 50 kilometers. To validate the single-station technique, they applied the exact same method to a magnitude 6.5 earthquake in Nevada recorded by a single seismometer in Australia. The test successfully pinpointed the correct fault.
The resulting data pointed to a strike-slip fault, where two crustal blocks slide horizontally past one another along a steep fracture, much like the San Andreas Fault in California. Eighty-two percent of the solutions that fit the wave data pointed to this family of movement. When matched with mapped fault networks, the source localized near Ius Chasma in the western reaches of the canyon.
Landslides and Impacts Cannot Explain Seismic Signals
Seismic signals on Mars do not automatically indicate tectonic shifting. Valles Marineris features extensive debris slopes, and meteorite impacts also shake the crust. The research team tested these alternative sources directly by modeling blast explosions and mass-wasting events.
Neither landslides nor impacts could replicate the polarity, timing, or horizontal shaking strength recorded by InSight. Images from the Context Camera on NASA's Mars Reconnaissance Orbiter revealed no fresh impact craters or massive new landslide scarps in the target area. Verified impacts on Mars typically produce high-frequency data, whereas S0976a registered as a low-frequency event.
Reevaluating the Origins of a Canyon Nine Times Longer Than Grand Canyon
Valles Marineris stretches nearly 3,900 kilometers long, reaches up to 600 kilometers wide, and plunges more than nine kilometers deep. It dwarfs Earth’s Grand Canyon, measuring roughly five times deeper and nearly nine times longer. Geologists have long debated whether the trench opened as a rift valley, collapsed under its own weight, or tore open via oblique pulling.
The recorded marsquake supports the oblique-tearing hypothesis rather than gravitational collapse. The stress pattern matches the compression estimated for the canyon’s early formation during the Hesperian period. Three forces likely load these ancient faults today: the thermal contraction of the cooling planet, the immense weight of the Tharsis volcanic rise, and the structural unloading caused by ongoing erosion within the canyon.
Unanswered Questions in Martian Seismology
Because InSight mission operations ended in December 2022 and no other seismometers currently operate on Mars, researchers must rely entirely on the archived data catalog. The study rests on a single marsquake captured by a single instrument.
While the findings confirm that ancient structures can still govern where the Martian crust breaks, the data nonetheless extract a dual reward from InSight’s historic mission log, illuminating both the planet’s deep core and the active tectonic scars stretching across its surface.
