What is the name of the vast canyon system on Mars that stretches about 4,000 kilometres?

Valles Marineris is the vast canyon system on Mars that stretches about 4,000 kilometres.

The system extends across roughly one-quarter of Mars’s circumference, mainly east of the Tharsis volcanic region. In places it reaches about 200 kilometres wide and up to around 7 kilometres deep. It is far longer and generally wider than Earth’s Grand Canyon, although the two features formed through different geological processes.

Valles Marineris is not a single narrow river-cut canyon. It is a connected network of enormous troughs, chasms, and smaller valleys. The system probably began as tectonic fracturing associated with the uplift and volcanic activity of Tharsis. Later landslides, wind erosion, and possible water or ice-related processes modified its walls and floors.

NASA’s Mariner 9 spacecraft provided the first detailed orbital views of the feature in 1971 and 1972. The name honours the Mariner program. Researchers continue to examine layered deposits inside the chasms because they preserve evidence about Mars’s ancient climate and geological history.