This 2,500-mile system is one of the larger canyons in the solar system.
Covering nearly a fifth the circumference of Mars, the canyon system Valles Marineris reigns as the largest canyon system on the red planet. Dwarfing its Earthly counterpart, the Grand Canyon, the Martian feature is one of the larger canyons in the solar system.
Valles Marineris is a system of canyons that spans 2,500 miles (4,000 kilometers). At some points, the canyon is 125 miles (200 km) wide. Regions can reach depths of 6 miles (10 km). If the system were located on Earth, it would stretch across the United States, from Los Angeles to the Atlantic coast.
By comparison, Earth's natural wonder, the Grand Canyon, is only 227 miles (446 km) long, 18 miles (30 km) wide, and 1 mile (1.6 km) deep. A windy channel on Venus, Baltis Valles, extends longer than the Martian system, as do a handful of rift valleys on Earth, which form along fault lines as the crust breaks apart.
Valles Marineris stretches east-west just below the Martian equator. It starts in the west in the Noctis Labyrinthus, a system of maze-like valleys and canyons, and stretches around 20 percent of the planet to the chaotic terrain near the Chryse Planitia basin.
The canyon system contains a number of different features that give clues to its formation. Collapse pits created by rushing water eating away at the land, massive floods, and seeping along canyon walls all point to water just at or beneath the surface at some point in the Martian history. Cracks in the crust, cliffs and walls, and landslides also exist along the expanse of Valles Marineris.
The vast canyon can be seen from Earth through a telescope as a dark scarring on the planet's surface. Features known as chasmata, steep depressions that resemble canyons on Earth, dominate the canyon.
The canyon begins in the Noctis Labyrinthus on the western edge, a region of material thought to have volcanic origins. Two parallel chasmata, Ius and Tithonium, stretch eastward, and contain lava flows and faults from the Tharsis Bulge.
Three more chasmata, Melas, Candor and Ophir, are connected on the east side of the parallel features. Their floors contain eroded material and volcanic ash. The floor of the Melas chasma contains the deepest point of the canyon system. Coprates Chasma lies farther east, with well-defined layered deposits. These deposits may have formed from landslides or wind-blown material, although the region may once have housed isolated lakes. Eos and Ganges are another set of chasmata that contain volcanic or windblown deposits that have slowly eroded over time.
The Valles Marineris system empties into the Chryse region, one of the lowest regions on Mars. Any water from the canyon system would have flown into the lowlands, and it may have once contained an ancient lake or ocean.