A new analysis of data from NASA’s InSight lander suggests that Mars’ enormous Valles Marineris canyon is still tectonically active, despite the planet’s surface being considered geologically “dead.” Researchers traced one of the largest marsquakes ever detected to a deep fault beneath the canyon, indicating that tectonic movement may continue long after the processes that formed the landscape ended.
On Aug. 25, 2021, InSight detected a powerful marsquake designated S0976a. The quake had a Mars-equivalent magnitude of 4.2, making it the strongest tremor observed by InSight or any other Mars lander at the time. A magnitude 4.7 marsquake detected in May 2022 later took the top spot, leaving S0976a as the second-largest recorded marsquake.
Unlike most marsquakes, which are small tremors caused by meteorite impacts near InSight, S0976a was a deep rumble that originated on the opposite side of the planet, in the western hemisphere near Valles Marineris.
In a new study published Oct. 15 in Nature Communications, researchers reanalyzed the seismic data from S0976a and concluded that the quake originated within a fault beneath the giant canyon. They argue that tectonic movement along this hidden fracture is the most likely explanation for the event.
“Valles Marineris is one of the most spectacular geological structures anywhere in the solar system, but until now, we did not know whether its faults were still active,” study lead author Jeonghun Song, a researcher in the Department of Earth Science and Engineering at Imperial College London, said in a statement.
“What we are seeing is that this is not simply a ‘dead,’ fossilized landform,” Song said. “Faults deep beneath the canyon can continue to slip and generate marsquakes long after the geological processes that originally formed it have stopped.”
A geologically “dead” world
Valles Marineris is a network of interconnected canyons and valleys stretching up to 2,500 miles (4,000 kilometers) across Mars—about 10 times the length of the Grand Canyon. It is also up to 20 times wider and five times deeper than the Grand Canyon. The feature is so vast that climbing out from its floor could potentially take months.
The enormous rift is named after the Mariner 9 spacecraft, which helped discover it in 1971. From space, it appears as a giant scar across the Martian surface. The nearby Tharsis region is also visible from orbit and contains some of Mars’ largest volcanoes, including Olympus Mons, which is at least three times taller than Mount Everest.
These features show that Mars was once geologically active, perhaps even more active than Earth. However, scientists think much of the planet’s surface has remained relatively unchanged for nearly 3 billion years, according to the European Space Agency.
Mars is thought to have become less active for two main reasons. First, the planet is smaller than Earth, so its core and mantle cooled much faster and are no longer as dynamic. Second, Mars does not have plate tectonics. Instead of its crust being divided into enormous plates that push against one another, the planet’s outer layer is mostly intact and acts like a giant lid over its cooling, partially molten interior.
A study published earlier this week challenged the idea that Mars is entirely inactive, suggesting that magma may still lie beneath some of the planet’s dormant volcanoes.
Mars nevertheless has fault lines. Rather than marking boundaries between tectonic plates, these faults resemble enormous cracks in the crust and are visible at the surface.
Signs of tectonic activity
The researchers found evidence of what is known as a strike-slip marsquake, in which blocks of crust move horizontally past one another along a steep, deep-rooted fault. They believe the movement occurred somewhere between 12 and 25 miles (20 and 40 kilometers) beneath Valles Marineris.
The team also simulated several other possible causes of the marsquake, including a large asteroid impact and landslides within the canyon. None of those scenarios could explain the observed pattern as well as tectonic movement.
“What makes this result compelling is that several completely different types of evidence all point in the same direction,” Song said.
The finding raises the possibility that similar tectonic activity could eventually be detected on other worlds in the solar system.
“Our work opens up the exciting possibility of discovering ongoing seismic activity on other planetary bodies that are considered geologically inactive,” Song said.
Mapping vibrations inside Mars
The study also highlights the value of detecting and analyzing marsquakes. InSight made the first officially confirmed detection of a marsquake in 2019. Scientists have since identified older quakes using data collected by the Viking landers in the late 1970s.
“S0976a turned out to be an unusual event,” study co-author Doyeon Kim, director of the Earth and Planetary Seismology Laboratory at Imperial College London, said in a statement. “Its waves traveled through the core, helping us probe the deepest parts of Mars. And now those waves are telling us what happened on Mars itself. From a single marsquake, we can learn about the center of Mars and about active faults beneath one of its most remarkable landforms.”
Scientists have also used InSight’s seismic vibrations to map Mars’ interior, leading to discoveries that include dozens of remnants from an ancient protoplanet, a possible hidden cause of the planet’s hemispheric asymmetry, a potentially active “mantle plume” and a huge underground reservoir containing enough liquid to cover Mars in an ocean 1 mile (1.6 kilometers) deep.
Unfortunately, InSight’s mission ended in December 2022 after dust accumulated on its solar panels. The reduced power eventually prevented the lander from sending signals back to Earth.
That means scientists currently have no way to detect new major marsquakes. However, the new research shows that InSight’s archived data can still produce important discoveries.
Song, J., Kim, D., Kolawole, F., Davis, J. M., Parry, R., & Maguire, R. (2026). Active crustal strain and fault reactivation in Valles Marineris. Nature Communications, 17(1).
Source: www.livescience.com