Imperial and Columbia team confirms active faulting beneath Valles Marineris

Researchers from Imperial College London and Columbia University have demonstrated that the largest canyon system in the solar system remains tectonically active. Analyzing data collected by NASA's InSight lander on 25 August 2021, the team established that the seismic event designated S0976a originated along a fault 20 to 40 kilometers beneath the surface of western Valles Marineris, according to imperial.ac.uk imperial.ac.ukimperial.ac.ukimperial.ac.ukOpen source ↗.

Mechanism of the S0976a rupture

Event S0976a was the sole seismic event located in the Martian western hemisphere during the InSight mission. By evaluating the amplitudes and propagation paths of the seismic waves through the planet, the researchers reconstructed the focal mechanism at the source imperial.ac.ukimperial.ac.ukimperial.ac.ukOpen source ↗. The data correspond to a strike-slip marsquake, wherein crustal blocks displaced horizontally along a steep, deeply rooted fault zone.

The investigators systematically modeled alternative mechanisms, including meteorite impacts and mass movements such as large-scale landslides. Neither mass-movement simulations nor subsequent orbital satellite imagery of the source region revealed impact craters or fresh debris slides capable of generating the observed waveform signatures imperial.ac.ukimperial.ac.ukimperial.ac.ukOpen source ↗. The findings confirm that the signal stems directly from tectonic slippage along pre-existing ancient fractures.

Crustal stress on a single-plate planet

Unlike Earth, Mars lacks mobile tectonic plates, functioning instead as a single cooling planetary shell. The team found that the orientation of the fault slip matches stress fields generated by long-term planetary cooling, lithospheric loading from the adjacent Tharsis volcanic province, and localized stress fields around the canyon itself imperial.ac.ukimperial.ac.ukimperial.ac.ukOpen source ↗.

Valles Marineris spans nearly 3,900 kilometers in length, up to 600 kilometers in width, and exceeds nine kilometers in depth. With this identification, the canyon joins Cerberus Fossae and southern Elysium Planitia as Martian regions exhibiting active faulting, demonstrating that internal lithospheric stresses vary locally across the modern Martian crust imperial.ac.ukimperial.ac.ukimperial.ac.ukOpen source ↗.