Valles Marineris, that cuts a wide swath across the face of Mars, is a system of canyons that runs along the Martian surface. This rift system is one of the larger canyons of the Solar System, surpassed only by the rift valleys of Earth and (in length only) by Baltis Vallis on Venus.
The Valles Marineris system is a network of interconnected valleys that begin in the west. The rift extends in a west-east direction just south of the Martian equator, on the east side of the Tharsis Bulge. It would stretch from Los Angeles to New York if it were on the Earth.
Noctis Labyrinthus is considered the starting point of the system, and then it moves east, to include the Tithonium chasmata and Ius chasmata. In the mid region are the Melas, Ophir, Coprates, Ganges, Capri, and Eos chasmata. The canyon moves through an area of chaotic terrain (ridges, cracks, and plains jumbled together) before it ends in the basin region of Chryse Planitia.
The entire system extends over 4000 km (2490 mi), covering nearly a quarter of the planet’s circumference and 59% of its diameter. Some parts of the canyon run as deep as 7 km (4 mi) and as wide as 200 km (125 mi). Valles Marineris dwarfs the Grand Canyon.
Most researchers agree that Valles Marineris is a large tectonic “crack” in the Martian crust that formed billions of years ago as the planet cooled, and was subsequently widened by erosional forces and collapsing of the rift walls. However, near the eastern flanks of the rift there appear to be some channels that may have been formed by water or carbon dioxide.
There have been many different theories about the formation of Valles Marineris since the 1970’s. One idea was erosion by water or thermokarst activity (the melting of permafrost in glacial climes). Liquid water can not exist in current Martian conditions, but has in the past, making the feature billions of years old. Another was that the canyons formed by withdrawal of subsurface magma. And then there was a theory of formation by tensional fracturing. The most agreed upon theory today is that Valles Marineris was formed by rift faults (like the East African Rift), later made bigger by erosion and collapsing of the rift walls. A rift valley is usually formed between two mountain ranges and is caused by the formation of the mountains. In this case, the formation is tied to the Tharsis Bulge.
Valles Marineris (latin for Mariner Valleys) was named after Mariner 9, the 1971-1972 mission that discovered it.
Image Credit: NASA/JPL/USGS