Researchers link a Mars quake to a deep fault beneath Valles Marineris

A study published in Nature Communications points to rocks slipping along a deep fault beneath Valles Marineris, the vast canyon system on Mars. The researchers interpret a quake recorded in 2021 as evidence that faults formed billions of years ago remain capable of moving under stress.

Earlier studies had placed the quake near western Valles Marineris, but its cause remained unclear. A meteoroid impact, a landslide or another movement of surface material could also have generated seismic waves—the vibrations that travel through a planet during a quake.

How the researchers tested the quake’s source

NASA’s InSight lander recorded the event, labelled S0976a, on August 25, 2021. The study was led by Jung-Hun Song of Imperial College London, with researchers from Columbia University and the University of Illinois Urbana-Champaign.

The team built models to test whether impacts, landslides or other movements of material could explain the recorded vibrations. Those models could not reproduce the observed waves. Images taken after the event by NASA’s Mars Reconnaissance Orbiter also showed no evidence of a corresponding impact crater or landslide.

The researchers’ best-fitting explanation was a strike-slip quake about 20–40 kilometres beneath the valley. In this kind of movement, blocks of crust slide horizontally past one another along a steep fault—a fracture in the rock. The wave pattern pointed to movement deep below the surface, while orbital observations showed long-lived fault systems in the region.

Analysis

Fault movement without moving plates

Mars has a single outer plate rather than the system of moving tectonic plates found on Earth. A fault can still slip within that outer shell. The researchers say their result is consistent with old faults moving under stresses associated with long-term cooling, volcanic activity and local conditions around the canyon; it does not establish Earth-like plate tectonics.