Mars’s Giant Canyon Is Still Alive Billions of years after it tore open, the solar system’s largest canyon system is still shifting. Scientists analyzing data from NASA’s InSight lander have found direct seismic evidence that a marsquake originated deep beneath Valles Marineris. The event, recorded on August 25, 2021, and labeled S0976a, was caused by rocks sliding sideways past one another along a steep fault roughly 20 to 40 kilometers (12 to 25 miles) below the surface. Valles Marineris stretches nearly 3,900 kilometers (2,400 miles) long, up to 600 kilometers (370 miles) wide, and more than 9 kilometers (5.6 miles) deep—nearly nine times longer, more than 20 times wider, and about five times deeper than the Grand Canyon at their greatest dimensions. Unlike Earth’s Grand Canyon, it was not carved primarily by a river. It formed as the Martian crust stretched and cracked during the rise of the massive Tharsis volcanic region. Mars lacks Earth’s moving tectonic plates. Its crust behaves more like a single, slowly cooling shell. Yet the new analysis shows that ancient faults created during the canyon’s formation can still rupture under modern stresses from planetary cooling, the weight of nearby Tharsis, and the canyon itself. Researchers ruled out alternative explanations such as meteoroid impacts or landslides. The seismic waves matched a strike-slip motion, and post-event orbital images showed no fresh impact crater or major new landslide. Multiple lines of evidence point to the same conclusion: the faults are not just a fossil landscape. They remain capable of generating marsquakes today. “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,” said lead author Jung-Hun Song of Imperial College London. “This is not just a ‘dead’ fossil landscape… Our study opens up exciting possibilities for discovering ongoing seismic activity on other planetary bodies that we might otherwise consider geologically inactive.” The finding adds Valles Marineris to a small set of regions—alongside Cerberus Fossae and southern Elysium Planitia—where InSight revealed active faulting on present-day Mars. Even though the mission ended in 2022, its data continue to reveal that the Red Planet is more dynamic than long assumed. Research by scientists at Columbia University and Imperial College London, published in Nature Communications. Credit for the original reporting: State of the Planet / Columbia Climate School.