|Astronomy Unbound. Bill Arnett. 2000.||"Valles Marineris: a system of canyons 4000 km long and from 2 to 7 km deep"||2-7 km|
|Considine, Glenn D. Van Nostrand's Scientific Encyclopedia. New York: Wiley, 2002.||"This huge equatorial canyon is about 2 km (1.2 miles) deep."||2 km|
|Hartman, William K. A Traveler's Guide to Mars. New York: Workman Publishing, 2000.||"According to the altitudes measured by the MGS laser instruments, parts of the Valles Marineris floor lie as much as 5.7 km below the mean surface of Mars, making it one of the lowest regions on the planet."||5.7 km|
|Lowell, Percival, Mapping Mars. New York: Workman Publishing, 1984.||"The depth of the canyon of Mars is 5 kms yet it varies because of landslides on the planet dipping it further into the planet."||5 km|
|Masda, Frank. Valles Marineris. Welcome to the Planets. NASA. 2003.||"Nearly half of the Valles Marineris canyon system is visible here. The entire system extends over 4000 km (2490 mi), covering about one fifth the circumference of Mars. Some parts of the canyon run as deep as 7 km (4 mi) and as wide as 200 km (125 mi). Compared to Valles Marineris, the Grand Canyon on Earth seems quite small at 446 km (277 mi) long, 30 km (18 mi) wide and 1.6 km (1 mi) deep."||7 km|
Valles Marineris is a vast canyon system that runs along the Martian equator just east of the Tharsis region. Valles Marineris is 4000 km (2500 miles) long and reaches depths of up to 7 km (4 miles). For comparison, the Grand Canyon in Arizona is about 800 km (500 miles) long and 1.6 km (1 mile) deep. In fact, the extent of the Valles Marineris is as long as the United States and it spans about 20 percent (1/5) of the entire distance around Mars.
The Valles Marineris was first discovered in 1971, by the spacecraft, Mariner 9. Mariner 9 was the very first obiter of Mars to reach Mars. During its years in orbit around Mars, it returned more than 7,329 images. These images provided the first global mapping of Mars. Mariner 9 also took the first detailed pictures of moons Phobos and Deimos. After discovering the great canyon, the scientists behind this mission decided to name it after he spacecraft, thus, it was named, Valles Marineris (Valley or Mariner).
The depth of the canyon varies from place to place. The depth has a range of 2000 meters to 7000 meters, since it was predicted that massive landslides causes parts of the surface of Mars to sink beneath the surface of Mars which causes a difference in depth.
Max Eisenstat -- 2004