Valles Marineris

How big is Valles Marineris?

About 3,870 km (2,400 mi) long, up to 600 km (370 mi) wide and about 9.3 km (5.8 mi) deep from rim to floor, NASA says.[1] It is long enough to stretch from California to New York.[1] Mars is 6,779 km (4,212 mi) wide,[19] so the canyon reaches nearly a fifth of the way around the planet.

Figures differ a little from source to source. ESA describes it as more than 4,000 km (2,500 mi) long and up to 700 km (435 mi) wide from north to south.[5] The USGS Gazetteer of Planetary Nomenclature, the official list of named features, gives the named system an extent of about 3,760 km (2,340 mi).[3] NASA’s figure covers the whole system, from Noctis Labyrinthus in the west to the broken ground in the east.[2]

Valles Marineris vs the Grand Canyon

Valles Marineris is nearly nine times as long as the Grand Canyon, about 20 times as wide at its widest and about five times as deep at its deepest. Those comparisons use NASA’s figures for Mars and the National Park Service’s for Arizona.[1][6][7]

Valles Marineris from NASA; Grand Canyon from the National Park Service. The ratios are our own, rounded. NASA describes Valles Marineris as more than 10 times longer and wider than the Grand Canyon.[1][6][7][8][9]

The two formed in different ways. A valley is either carved by water or ice, or made by the crust pulling apart, which geologists call rifting, the National Park Service explains.[8] The Grand Canyon is the first kind: the region was lifted between 70 and 30 million years ago, and the Colorado River began cutting down through it 5 to 6 million years ago.[8] Valles Marineris is thought to be mostly the second kind.[4][12]

Is Valles Marineris the largest canyon in the solar system?

Yes. NASA calls it the largest canyon in the solar system,[1] and ESA calls it “the biggest and most dramatic canyon system in the Solar System.”[5] It isn’t a single canyon but several parallel, connected troughs.[12] NASA’s own image pages call it the Grand Canyon of Mars.[2][9]

How did Valles Marineris form?

Mostly by the crust cracking and pulling apart, then widening as its walls collapsed. Geologists think it began to open along faults about 3.5 billion years ago, NASA says. As magma pushed into Tharsis, the giant volcanic region just to the west, the whole region rose, and the crust around it stretched and broke.[9] As the cracks opened, the ground between them sank, “much as the keystone in an arch drops when the ends of the arch move apart.”[9] On Earth, the same kind of process is happening on a smaller scale in the Kenya rift in East Africa, ESA says.[4]

The faults also let water escape from underground, which undermined the ground. The steep new walls collapsed in landslides that widened the canyon further.[9] Below one wall in the central canyons, landslide debris traveled up to 70 km (43 mi).[4] The main growth seems to have stopped about 2 billion years ago, though small landslides still happen in places, NASA says.[9] Olympus Mons and the other Tharsis volcanoes have their own page.

The story isn’t settled. ESA says it remains unclear how the canyon formed, and notes another idea: ice under the surface melted, the water drained away, and the ground above the empty spaces collapsed.[4] Huge ancient river channels start in the broken ground at the canyon’s eastern end and run north.[2] Laser maps from NASA’s Mars Global Surveyor turned up a surprise there: part of the eastern canyon lies about 1 km (half a mile) below the nearby outflow channels and slopes away from them.[13]

What are the parts of Valles Marineris?

From west to east: a maze of valleys, a chain of deep canyons called chasmata, and broken ground where it ends. A chasma is “a deep, elongated, steep-sided depression,” in the official terms for planetary features.[18] Lengths below are each feature’s extent in the Gazetteer.[17]

• Noctis Labyrinthus. A complex of intersecting valleys at the western end, toward Tharsis, about 1,190 km (740 mi) across.[2][17][18]
• Ius and Tithonium Chasmata. Two long canyons side by side in the west, each roughly 800 km (500 mi) long.[17]
• Melas, Candor and Ophir Chasmata. The center of the system, where it is widest from north to south.[4] Candor Chasma holds layered deposits up to 3 km (2 mi) tall.[14]
• Coprates Chasma. A trough about 960 km (600 mi) long, running east from the central canyons.[17]
• Ganges, Capri and Eos Chasmata. The eastern canyons, where the system opens into chaotic terrain. In the official terms, a chaos is a “distinctive area of broken terrain.”[2][17][18]

What is inside the canyon?

Thick layers of sediment, some holding minerals that form in water. Light-toned, finely layered deposits sit inside the canyons, unlike the rugged rock of the rims. They have puzzled scientists for decades. Ideas include lake deposits, windblown dust and sand, or volcanic material that erupted after the canyon formed.[14] One of them, Ceti Mensa in west Candor Chasma, rises 3 km (2 mi) above the canyon floor.[14]

Instruments that identify minerals from orbit found hydrated sulfate salts, such as gypsum and kieserite, in these deposits: OMEGA on ESA’s Mars Express and CRISM on NASA’s Mars Reconnaissance Orbiter. On Earth these minerals usually form in wet places.[14] In a mound in east Candor Chasma, CRISM found layers of two kinds of sulfate taking turns. The layers show no signs of slumping or channels, so still water, or material settling from the air, are the likeliest origins, the HiRISE team says.[15]

CRISM also found opal-like hydrated silica, often in thin layers that run for long distances around the rim and sometimes inside the canyon. It formed where liquid water altered volcanic or impact material. In 2008 NASA said the find suggests liquid water lasted on Mars until perhaps 2 billion years ago, a billion years later than scientists had believed.[16] Water on Mars covers the bigger story.

Why is it called Valles Marineris?

It is named for NASA’s Mariner 9 mission. The International Astronomical Union adopted the name in 1973 to honor the mission’s science team.[3] The name is Latin; the THEMIS team at Arizona State University translates it as “Mariner Valley.”[3][12]

Mariner 9 reached Mars on Nov 14, 1971, and became the first spacecraft to orbit another planet. A planet-wide dust storm hid the surface at first, and photos taken before about mid-January 1972 showed little detail.[10][11] Once the dust cleared, the orbiterOrbiterAn orbiter circles Mars without landing, studying the planet from above — and many also relay rover data back to Earth.More in the glossary gave the first detailed views of the canyon system.[10][11]

The best pictures of Valles Marineris

Orbiters have photographed it from end to end, from NASA’s Viking missions to ESA’s Mars Express.

• Viking mosaic. NASA joined 102 images from Viking Orbiter 1 into one view of the whole canyon system, with the three big Tharsis volcanoes to the west.[2]
• THEMIS mosaic. Released in 2006, this view from NASA’s Mars Odyssey combines more than 500 daytime infrared images. Details as small as about 100 m (328 ft) show.[9]
• Mars Express color views. ESA’s High Resolution Stereo Camera has imaged the central canyons at about 21 to 30 m (69 to 98 ft) per pixel.[4] A global color mosaic made in 2023 for the mission’s 20th anniversary shows sulfate deposits, and fog and haze lying in the canyon’s depths.[5]
• HiRISE close-ups. This camera on NASA’s Mars Reconnaissance Orbiter shows single layers in the deposits, such as the cliffs of Ceti Mensa and the layered mound in east Candor Chasma.[14][15]

Valles Marineris is one of the big landmarks on the surface of Mars. The other giant scar in Mars’s crust is the Hellas impact basin.

Sources

1. NASA Science — Mars: FactsPrimary · checked Oct 6, 2026
2. NASA Science — Valles Marineris: The Grand Canyon of Mars (PIA04304)Primary · checked Oct 6, 2026
3. USGS / IAU — Gazetteer of Planetary Nomenclature: Valles MarinerisPrimary · checked Oct 6, 2026
4. ESA — Melas, Candor and Ophir Chasmas: centre of Valles MarinerisPrimary · checked Oct 6, 2026
5. ESA — Close-up of Valles Marineris from global Mars colour mosaic (annotated)Primary · checked Oct 6, 2026
6. U.S. National Park Service (Grand Canyon) — Park StatisticsPrimary · checked Oct 6, 2026
7. U.S. National Park Service (Black Canyon of the Gunnison) — Canyon DimensionsPrimary · checked Oct 6, 2026
8. U.S. National Park Service (Grand Canyon) — GeologyPrimary · checked Oct 6, 2026
9. NASA Science — The Grand Canyon of Mars – Valles Marineris (13 Mar 2006)Primary · checked Oct 6, 2026
10. NASA Science — Mariner 9Primary · checked Oct 6, 2026
11. NASA NSSDCA — Mariner 9 (1971-051A)Primary · checked Oct 6, 2026
12. Arizona State University, Mars Odyssey THEMIS team — Valles Marineris, a Martian Rift ZonePrimary · checked Oct 6, 2026
13. NASA Goddard Space Flight Center — Mars Topography (MOLA)Primary · checked Oct 6, 2026
14. HiRISE, University of Arizona — A Window into the Past (ESP_051841_1750)Primary · checked Oct 6, 2026
15. HiRISE, University of Arizona — Mound of Layers in East Candor Chasma (PSP_006968_1735)Primary · checked Oct 6, 2026
16. NASA JPL — NASA Orbiter Reveals Details of a Wetter MarsPrimary · checked Oct 6, 2026
17. USGS / IAU — Gazetteer of Planetary Nomenclature: MarsPrimary · checked Oct 6, 2026
18. USGS / IAU Gazetteer of Planetary Nomenclature — Descriptor Terms (Feature Types)Primary · checked Oct 6, 2026
19. NASA NSSDCA — Mars Fact SheetPrimary · checked Oct 6, 2026