Mars' Grand Canyon Is Still Tectonically Active, Study Finds

How did researchers find the marsquake?

The story begins on August 25, 2021, when NASA's InSight lander detected a tremor from its position in Elysium Planitia, on the opposite side of Mars from Valles Marineris. At first, researchers could not be sure it was a quake at all. Tremors on Mars can also come from landslides or meteorite impacts.

The event, named S0976a, turned out to be extraordinary. Its seismic waves had traveled through Mars' core, allowing scientists to study the planet's deepest interior. Its epicenter lay somewhere in the western Valles Marineris region, though its exact location and cause remained obscure.

The new research closed that gap. By analyzing the amplitudes and directions of the seismic waves, the team pinpointed the epicenter 12 to 25 miles (20 to 40 km) beneath the canyon and reconstructed what caused it.

Co-author Doyeon Kim of Imperial College London said: "S0976a has turned out to be an extraordinary event, playing an important role in our understanding of the red planet. Its waves traveled through the core and helped us investigate the deepest part of Mars, and now they are telling us what happened at the source itself. From a single marsquake, we can learn both about the center of the planet and about an active fault beneath one of its most remarkable landscapes."

What kind of quake was it?

The researchers concluded that a strike-slip marsquake was the most likely cause. A strike-slip event occurs when two chunks of crust move horizontally past one another along a steep fault with a deep root — the same basic mechanism as the San Andreas Fault, though on a planet with no moving plates.

Lead author Jung-Hun Song of Imperial College London said: "What makes the result compelling is that several completely different types of evidence point in the same direction. The seismic waves tell us that there was a sideways sliding motion on a fault well below the surface, while the geology seen from orbit shows a region crossed by long-lived fault systems."

Song added: "What we see is that this is not just a 'dead' fossil landscape, as faults deep beneath the canyon can still slip and generate marsquakes, long after the geological processes that originally formed them have ceased."

What comes next?

The result carries a built-in limitation. InSight ceased operations in 2022 after dust accumulated on its solar panels, and no active lander is currently recording marsquakes on the surface. Follow-up observations are, for now, impossible.

The next marsquake may go unrecorded until astronauts stand on the red planet and feel it shake beneath them.