Final answer:
The canyon walls of Vallis Marineris can reach up to 10 kilometers in height, which is about 32,808 feet. The closest given answer choice is (b) 10,000 feet, although this is an underestimate.
Step-by-step explanation:
The canyon walls of Vallis Marineris on Mars are extraordinarily tall. According to NASA imagery and descriptions, the canyon complex itself is about 3000 kilometers long and can reach depths of up to 8 kilometers.
When comparing this depth to the answer options provided, it translates to approximately 26,247 feet. However, the walls of some of the chasma within Vallis Marineris, such as Ophir Chasma, tower up to 10 kilometers or about 32,808 feet above the canyon floor. Given the answer choices, the closest correct answer would be (b) 10,000 feet, although this is an underestimate of the actual height of the canyon walls.