Valles Marineris

Valles Marineris is a huge system of canyons on the planet Mars. It was named after the Mariner 9 spacecraft that first discovered it in 1971–72. This canyon is the largest in our whole Solar System. It stretches for more than 4,000 kilometers, which is about a quarter of Mars's circumference, and it can be up to 7 kilometers deep.

The canyon runs along the equator of Mars, just to the east of a big volcanic area called Tharsis. It starts in a place known as Noctis Labyrinthus and then continues with many sections such as Tithonium, Ius, Melas, Candor, Ophir, Coprates Chasma, Ganges, Capri, and Eos. Finally, it ends in a flat area called Chryse Planitia.

Scientists think Valles Marineris might have started as a big crack in Mars's surface caused by the planet's changing shape. Over time, wind, water, or even lava from nearby volcanoes may have made the canyon even wider and deeper. This amazing feature helps us learn more about the history and geology of Mars.

Formation

The most agreed upon theory today is that Valles Marineris was formed by rift faults, later enlarged by erosion and collapsing of the rift walls, similar to how the East African Rift was formed. The formation of Valles Marineris is thought to be closely tied with the formation of the Tharsis Bulge. The Tharsis Bulge was formed from the Noachian to Late Hesperian period of Mars, in three stages.

Landslides have left deposits on the floor of Valles Marineris and helped to widen it. Possible triggers of these landslides are quakes caused by tectonic activity or impact events. Mars is much less tectonically active than Earth, and large quakes are unlikely to have caused these landslides. However, some craters may have formed and caused some of the landslides.

Regions of Valles Marineris

Noctis Labyrinthus is located on the western edge of the Valles Marineris Rift System, north of the Syria Planum and east of Pavonis Mons. This area features a jumbled terrain made of huge, fractured blocks. These blocks have canyons running in different directions and surround larger blocks of older land. The upper parts of these blocks are made of younger, fractured material that seems to come from volcanic activity linked to the Tharsis bulge. The sides of the blocks consist of undivided material believed to be basement rock. The spaces between the blocks have either rough or smooth floor material. The rough material is thought to be debris from the walls, while the smooth material might be from flowing water or lava.

Further east are Ius and Tithonium chasmata, running parallel to each other with Ius to the south and Tithonium to the north. Ius is wider and leads to Melas Chasma, featuring a central ridge called Geryon Montes made of undivided basement rock. The floor of Ius Chasma is mostly made of landslide material, while its walls have short valleys stretching out, similar to features near the Grand Canyon. Tithonium Chasma looks much like Ius but lacks these valley features on its south side and has a small area of smooth floor material that seems to be eroded ash.

The next part of Valles Marineris includes three chasmata: Melas, Candor, and Ophir. Melas Chasma’s floor is about 70% younger material, likely volcanic ash shaped by wind, mixed with rough material from eroded canyon walls. Between Candor and Melas chasmata, the floor has grooved material, possibly from ancient water or ice, along with layers of volcanic ash.

Coprates Chasma, further east, resembles Ius and Tithonium chasmata but has distinct layered deposits that might be from ancient lakes or repeated landslides. Near its deepest point, the canyon could have held a lake over a kilometer deep before spilling over.

To the east lie Eos and Ganges chasmata. Eos Chasma’s western floor is etched massive material, possibly volcanic or wind-deposited, while its eastern end shows streamlined bars and striations from ancient flowing water. Ganges Chasma, a branch of Eos, has a floor made of alluvial deposits from its canyon walls.

Finally, Valles Marineris flows into the Chryse region, emptying into the northern plains of Mars. This area features chaotic terrain and outflow channels similar to flood-scarred lands on Earth, suggesting ancient catastrophic flooding on Mars.