What is the name of Mars’s largest canyon system?

Valles Marineris is the name of Mars’s largest canyon system.

This immense network of valleys stretches roughly 4,000 kilometres across Mars, near the equator. It is far longer and wider than Earth’s Grand Canyon, though it formed through different geological processes and is not simply a scaled-up river canyon.

The system includes several connected troughs, including Tithonium Chasma, Coprates Chasma, and Melas Chasma. Scientists generally link its origin to enormous crustal fracturing associated with the rise of the Tharsis volcanic region.

The name honours NASA’s Mariner 9 mission, which photographed the feature in detail in 1971. Valles Marineris is commonly called a canyon, but the term describes a complex tectonic rift system as well as eroded valleys.