NASA’s InSight lander recorded a low-frequency marsquake on August 25, 2021, originating 20 to 40 kilometers beneath Valles Marineris. Researchers from Imperial College London and Columbia University concluded that the largest canyon system in the solar system remains tectonically active today, driven by ancient faults slipping inside a cooling, single-plate planet.
Marsquakes Reveal Faults Beneath Valles Marineris
Planetary scientists long viewed Mars as a geologically quiet world. Its crust behaved as a single stagnant lid without the grinding movement of tectonic plates seen on Earth.
That view changed when researchers analyzed data from a seismic event designated S0976a, recorded by NASA’s InSight lander on August 25, 2021. The signal was unique because it originated on the opposite side of the planet from the lander.
By examining the amplitudes and directions of the seismic waves as they traveled through the Martian interior, the team mapped the source to a depth of 20 to 40 kilometers beneath Valles Marineris. The data revealed a strike-slip marsquake event, where distinct blocks of the crust slid horizontally past one another along a steep fault.
Researchers tested alternative explanations, including meteorite impacts and surface landslides. Satellite images captured by NASA’s Mars Reconnaissance Orbiter showed no fresh impact craters or slide zones.
Models of mass-wasting events failed to reproduce the specific wave timings and strong horizontal shaking recorded by the lander.
Valles Marineris is one of the most spectacular geological structures anywhere in the solar system, but until now we didn’t know for certain that its faults are still active.
Jung-Hun Song, lead author of the study from Imperial’s Department of Earth Science and Engineering
Measuring the Grand Canyon of Mars
The canyon system dwarfs any terrestrial geological feature. Valles Marineris stretches nearly 3,900 kilometers across the Martian surface, reaches up to 600 kilometers in width, and plunges more than nine kilometers deep. Those dimensions make it roughly nine times longer, more than 20 times wider, and about five times deeper than Earth’s Grand Canyon at their respective maximum measurements.
| Feature | Valles Marineris (Mars) | Grand Canyon (Earth) |
|---|---|---|
| Maximum Length | Nearly 3,900 kilometers | Not specified |
| Maximum Width | Up to 600 kilometers | Not specified |
| Maximum Depth | More than nine kilometers | Not specified |
Geologists proposed mechanisms ranging from tensional tectonic forces linked to the volcanic Tharsis region during the Noachian and Late Hesperian periods to gravitational collapse and erosion. The confirmation of active faulting inside the canyon provides fresh evidence that structures formed billions of years ago still dictate where the crust breaks under modern stresses.
Deep Martian Faults Can Still Rupture
Unlike Earth, where moving tectonic plates continuously create and destroy fault zones, Mars operates under a single, slowly cooling lid. Scientists previously assumed that faults within such a rigid shell would heal and strengthen over time, rendering ancient canyon systems entirely dormant. The new findings demonstrate that deep pre-existing faults can remain weak enough to rupture under contemporary pressures.
This makes our new results particularly important as Mars gives us a very different natural experiment,
said study co-author Folarin Kolawole, an assistant professor at Columbia University. The orientation of the S0976a faulting aligns with stresses generated by the planet’s long-term cooling, volcanic stresses, and local forces tied directly to the canyon.
InSight Data Reveals Active Faulting in Valles Marineris
The study adds Valles Marineris to a small set of regions where InSight data have revealed active modern faulting. Although the InSight mission is no longer operational, the archived seismic catalog continues to yield discoveries.
S0976a has turned out to be an extraordinary event, playing an important role in our understanding of the Red Planet.
Not specified
Researchers noted that the seismic waves from S0976a previously traveled through the Martian core to map the planet’s deepest interior layer. The publication of the findings in Nature Communications links the same single event to the mechanics of an active fault beneath its most famous canyon.