Valles Marineris

Valles Marineris runs broadly east–west along Mars’s equatorial region, just east of Tharsis. NASA describes it as about 2,500 miles (4,000 kilometres) long and up to 4 miles (about 7 kilometres) deep, spanning roughly one-fifth of the planet’s circumference. ESA gives dimensions of more than 4,000 kilometres long, about 200 kilometres wide and locally as much as 10 kilometres deep. These figures are approximate and vary with the boundaries and measurement used. The system consists of linked valleys and chasms rather than one uniform trench.

The western end includes the fractured terrain of Noctis Labyrinthus, while long chasms and broad depressions dominate much of the central region. Farther east, the terrain includes broad valleys and chaotic ground. Steep walls, faults, landslide deposits and varied canyon floors record a complex geological history.

The leading explanation is that Valles Marineris began as a major rift or set of fractures in the Martian crust. NASA links its formation to stresses associated with crustal and interior cooling and the Tharsis region; ESA describes the crust as stretching as the Tharsis bulge developed, then faulting and collapsing into troughs. The precise sequence and contribution of individual processes remain subjects of research. Erosion, landslides and other mass-wasting processes have modified the chasms, and orbital observations indicate that water altered some of the terrain after the initial structures formed.

Valles Marineris has been mapped in detail by orbiting spacecraft. ESA’s Mars Express assembled a broad view from observations across multiple orbits, while NASA provides a three-dimensional representation based on spacecraft data. Orbital imaging and topographic measurements let researchers compare canyon walls, floors and surrounding terrain to investigate how the system formed and changed.